Motorcycle tyre

Abstract

A tyre (1 ) for motorcycle wheels is described comprising an equatorial plane (X- X) free from transversal grooves and a tread band (8) extending according to an axial development (L), wherein the tread band (8) comprises, in a plan development thereof, two lateral annular portions (L2, L3) arranged on opposite sides with respect to said equatorial plane (X-X) and each comprising a first lateral annular sub-portion (L2', L3'), proximal with respect to the equatorial plane (X-X), and a second lateral annular sub-portion (L2", L3"), distal with respect to the equatorial plane (X-X). In the tread band (10), a plurality of transversal grooves (12) is defined, which are formed in the lateral annular portions (L2, L3), each having an axial extension equal to at least 30% of the axial half-development (L / 2) of the tread band (10) and a first directrix (g') forming with the equatorial plane (X-X) an angle (alpha) having a minimum value (alpha'a) comprised between 15° and 50° at an end (12'a) proximal to the equatorial plane (X-X). The transversal grooves (12) form a circumferential succession of transversal ribs (13) extending up to the axial ends of the tread band (10) and having a first portion (13') having an increasing width moving away from the equatorial plane (X-X) in a first annular sector (S) proximal to the equatorial plane (X-X).

Description

[0001] Motorcycle tyre

[0002] Field of the invention

[0003] The present invention refers to a tyre for two / three-wheeled vehicles controlled essentially by the inclination (camber) of the wheels.

[0004] In the rest of the description and in the following claims, such a type of tyre will also be indicated by the name “motorcycle tyre”.

[0005] In particular, the present invention refers to a high-performance tyre intended to be mounted on the front or rear wheel of two-wheeled racing or track motorcycles but also approved for road use.

[0006] Related Art

[0007] Two-wheeled motorcycle tyres are known for example from patent application EP 1 473 176 A1 and from patent application EP 1 918 131 A1.

[0008] Summary of the invention

[0009] In relation to two-wheeled motorcycles belonging to the racing segment, the Applicant has noted an increasing demand for tyres that perform well both in demanding sports driving (for example on track), and in the case of supersports motorcycles approved for road use, for road uses of the motorcycle throughout the year in wet or humid surface conditions and / or in cold weather conditions or conditions of non-optimal road surface, all in combination with good resistance to wear.

[0010] In order to provide a motorcycle tyre in which it is possible to obtain both resistance to wear and driving stability on wet ground, the aforementioned patent application EP 1 473 176 A1 describes a first tyre having a tread pattern comprising a pair of zigzag circumferential grooves having a width in the axial direction such as to prevent sudden detachment of the zigzag groove from the ground contacting area of the tyre so as to suppress the deterioration of the driving stability on wet ground.

[0011] In accordance with this document, when the camber angle increases, the water present under the ground contacting area is drained from substantially curvilinear grooves, axially arranged externally to the zigzag-shaped circumferential grooves, and comprising a first axially inner portion with high inclination forming an angle comprised between 0° and 20° with respect to the equatorial plane of the tyre and PIR478B

[0012] 2 a second axially outer portion with ever decreasing inclination towards the shoulder areas of the tyre.

[0013] Thanks to this configuration of the tread pattern, the tread band portions defined in the shoulder areas of the tyre between the axially outer portions of the substantially curvilinear grooves have a stiffness that is said to be capable to withstand the stresses in the presence of high camber angles so that the resistance to wear is high.

[0014] Patent application EP 1 473 176 A1 also describes a comparative tyre, illustrated in Fig. 8 of this document, provided with a tread pattern comprising a first plurality of inclined grooves extending from the end of the tread band to the equatorial plane of the tyre and ending in proximity thereto, and a second plurality of inclined grooves having a smaller axial extension and alternately arranged between the grooves of the first plurality of grooves. Furthermore, the first and second inclined grooves are circumferentially arranged offset with each other along the tread band.

[0015] In relation to the comparative tyre described in Figure 8 of patent application EP 1 473 176 A1 , the Applicant has observed that this tyre has in the tread band portion spanning from the equatorial plane of the tyre to the axially inner end of the grooves having a smaller axial extension a discontinuity in the width of the ribs defined between circumferentially consecutive grooves (and therefore a discontinuity in the width of the tyre solid part that can discharge the stresses imparted to the tyre itself on the ground) that can negatively affect the dynamic behaviour of the tyre when the camber angle changes from travel along a straight course to cornering.

[0016] In particular, the Applicant has observed that shifting from travel along a straight course (in which the tyre is substantially perpendicular to the ground) to a slight bend of the motorcycle, the configuration of the tread pattern with inclined grooves of different axial extension alternated with each other can trigger a discontinuity in the type of interaction between the tyre and the ground that can jeopardize the handling and traction performance in wet or humid driving conditions giving the rider driving sensations (or feeling) that do not allow to fully exploit the power of the motorcycle in a sport type driving or in races.

[0017] This results in an undesirable worsening of the driving safety characteristics as the camber angle increases, particularly on a wet or humid ground. PIR478B

[0018] 3

[0019] The aforementioned patent application EP 1 918 131 A1 discloses a motorcycle tyre purportedly capable of improving cornering performance on wet ground with respect to conventional tyres.

[0020] This motorcycle tyre comprises a tread pattern consisting of a central portion of the tread having an axial extension equal to 60% of the axial extension of the tread and lateral portions of the tread pattern arranged outside of the central portion of the tread in the direction of the axial extension of the tyre.

[0021] In the central portion of the tread pattern a plurality of circumferential grooves is formed, arranged on opposite sides of the equatorial plane of the tyre, whereas in the lateral portions of the tread pattern a plurality of inclined grooves is formed connected to the axially outermost circumferential grooves and forming a fixed angle with respect to a transversal direction of the tyre. The inclined grooves are circumferentially arranged pitch-wise so as to define therebetween a corresponding plurality of inclined ribs.

[0022] The inclined grooves comprise wide and narrow grooves inclined at an angle of less than 90° with respect to the circumferential direction of the tyre so that the grooves extend continuously over a region of 50% or more of an axial extension of the lateral portion of the tread.

[0023] In relation to the tyre described by patent application EP 1 918 131 A1 , the Applicant has observed that also in this case when shifting from travel along a straight course (in which the tyre is substantially perpendicular to the ground) to a slight bend of the motorcycle, the configuration of the tread pattern with inclined grooves connected to the circumferential grooves can trigger discontinuity in the type of interaction between the tyre and the ground that can jeopardize the handling and grip performance in the driving conditions on wet ground.

[0024] In particular, the Applicant has observed that with a tyre of this type when shifting from travel along a straight course to a slight bend of the motorcycle, there can be a deterioration in the grip of the motorcycle that can imply a worsening in confidence and driving comfort, in particular in sports type driving or in races.

[0025] In its search for a further improvement in the driving and grip performance on wet or humid ground and / or in cold weather or in non-optimal road surface conditions of a motorcycle tyre, the Applicant has surprisingly found that it is possible to achieve a substantial improvement in terms of consistency of such performance PIR478B

[0026] 4 as the camber angle of the tyre changes with a suitable configuration of the tread pattern.

[0027] In particular, the Applicant has surprisingly found that it is possible to achieve the aforementioned objective thanks to a combination of the following provisions:

[0028] - forming, in lateral annular portions of the tread band, transversal grooves obliquely extending with respect to the equatorial plane of the tyre and having a first groove portion lying in a first lateral annular sub-portion of the tread band proximal to the equatorial plane of the tyre and a second groove portion lying in a second lateral annular sub-portion of the tread band distal with respect to the equatorial plane of the tyre;

[0029] - arranging the transversal grooves next to each other along the circumferential development of the tyre so as to define a circumferential succession of transversal ribs extending up to the axial ends of the tread band;

[0030] - defining in an annular sector of the first lateral annular sub-portion of the tread band proximal to the equatorial plane transversal ribs having a width that increases moving away from the equatorial plane; and

[0031] - suitably inclining the transversal grooves in a portion thereof proximal to the equatorial plane of the tyre.

[0032] In one aspect, the present invention therefore relates to a motorcycle tyre as defined in the attached claim 1 .

[0033] More particularly, said tyre comprises an equatorial plane free from transversal grooves and a tread band extending according to an axial development.

[0034] Preferably, the tread band comprises, in a plan development thereof, two lateral annular portions arranged on opposite sides of the central annular portion with respect to the equatorial plane of the tyre.

[0035] Preferably, the lateral annular portions of the tread band each comprise a first lateral annular sub-portion, proximal with respect to the equatorial plane, and a second lateral annular sub-portion, distal with respect to the equatorial plane.

[0036] Preferably, the tread band comprises a plurality of transversal grooves formed in the lateral annular portions of the tread band having an axial extension equal to at least 30%, of the axial half-development of the tread band. PIR478B

[0037] 5

[0038] Preferably, said first lateral annular sub-portion of the lateral annular portions axially extends along 10%-32% of the axial development of the tread band.

[0039] Preferably, said first lateral annular sub-portion of the lateral annular portions comprises a first annular sector proximal with respect to the equatorial plane.

[0040] Preferably, said first annular sector axially extends along 7%-32% of the axial development of the tread band.

[0041] Preferably, said transversal grooves comprise a first groove portion lying in said first lateral annular sub-portion and a second groove portion lying in said second lateral annular sub-portion of the tread band.

[0042] Preferably, the first groove portion of the transversal grooves has a first directrix forming with the equatorial plane of the tyre an angle having a minimum value comprised between 15° and 50° at an end of the first groove portion proximal to the equatorial plane and a maximum value comprised between 50° and 80° at an end of the first groove portion distal with respect to the equatorial plane.

[0043] Preferably, said transversal grooves are arranged according to a circumferential succession configured so as to form between the transversal grooves a circumferential succession of transversal ribs extending up to the axial ends of the tread band.

[0044] Preferably, said transversal ribs comprise a first transversal rib portion lying in said first lateral annular sub-portion and a second transversal rib portion lying in said second lateral annular sub-portion.

[0045] Preferably, in said first lateral annular sub-portion a reference system is defined comprising a plurality of axially adjacent annular areas each having an axial extension equal to 3% of the axial development of the tread band.

[0046] Preferably, in the first annular sector of the first lateral annular sub-portion of the lateral annular portions, the aforementioned first transversal rib portion has a width, as defined in the present document, increasing moving away from the equatorial plane between an axially inner end of the first annular sector proximal to the equatorial plane and an axially outer end of the first annular sector distal with respect to the equatorial plane.

[0047] Preferably, in said first annular sector defined in the first lateral annular subportion and moving away from the equatorial plane of the tyre, the width of the PIR478B

[0048] 6 first transversal rib portion increases passing from a given annular area to an axially adjacent annular area of said reference system.

[0049] Preferably, the second groove portion of the transversal grooves has a second directrix forming an angle comprised between 50° and 80° at an end of the second groove portion proximal to the equatorial plane.

[0050] Preferably, the second groove portion of the transversal grooves has a second directrix forming an angle comprised between 80° and 90° with reference to the equatorial plane, or to a plane parallel to the equatorial plane and passing through the axially outer end of the tread band, according to the definition reported above, at an end of the second groove portion distal with respect to the equatorial plane.

[0051] Preferably, said second transversal rib portion has a substantially constant width comprised between 5% and 60% of an axial half-development of the tread band.

[0052] Without wishing to be bound by any interpretative theory, the Applicant considers that by adequately limiting the width increase of the first transversal rib portion in the first annular sector of the first lateral annular sub-portion and moving away from the equatorial plane and by adopting an appropriate angle arrangement of the transversal grooves with respect to the equatorial plane of the tyre, it is possible to have a very homogeneous handling response by varying the camber angle when shifting from travel along a straight course (with a camber angle substantially equal to 0°) to travel conditions with slight bend (for example with camber angles less than 30°).

[0053] More in particular, the Applicant has found that thanks to the aforementioned characteristics of the tread pattern it is advantageously possible to obtain an improvement of the thrust during braking or acceleration of the tyre thanks to a “continuity” of shape and size of the ribs along the circumferential direction under the ground contacting area of the tyre as the camber angle increases (i.e. entering or exiting a bend).

[0054] The Applicant has in fact experimentally observed that the aforementioned configuration of the tread pattern allows to achieve an important improvement in terms of constancy of driving and grip performance of the tyre in wet or humid conditions and / or in cold weather or non-optimal road conditions as the camber angle of the tyre changes.

[0055] Still without wishing to be bound by any interpretative theory, the Applicant considers that the achievement of this technical effect can be correlated to the PIR478B

[0056] 7 fact that the aforementioned gradual width increase of the ribs in the first annular sector of the first lateral annular sub-portion of the tread band and moving away from the equatorial plane of the tyre allows to have a dynamic behaviour of the vulcanised elastomeric material that forms the same ribs that varies “continuously” in relation to its ability to absorb the stresses imposed on the material when the camber angle varies, in particular at low bend angles.

[0057] The Applicant has in particular experimentally found in track tests, which will be discussed below, that the tyre of the invention, in particular a front motorcycle tyre, allows the driver to have a significantly improved driving confidence (“feeling”) when shifting from travel along a straight course (with a camber angle substantially equal to 0°) to travel conditions with slight bend (for example with camber angles less than 30°) on a wet ground.

[0058] This translates into an increased safety feeling of the driver that allows him to follow several trajectories and therefore to improve the so-called “limit” performance, achieving significant improvements in terms of lap time in case of sports use and significantly improved safety margins in the case of road use.

[0059] All this, while maintaining both an optimal water draining performance under the ground contacting area of the tyre, and an adequate wear resistance performance of the tyre itself.

[0060] For the purposes of the present invention, the following definitions apply.

[0061] The term “motorcycle tyre” is used to indicate a tyre having a high curvature ratio, typically greater than or equal to 0.20 and lower than or equal to 0.40 for a rear tyre and greater than or equal to 0.20 and lower than or equal to 0.50 for a front tyre, and capable of reaching high camber angles (for example 50°-60°) while driving the motorcycle along a bend.

[0062] The term “tread pattern” is used to indicate the representation of all of the points of the tread band (grooves included) on a plane perpendicular to the equatorial plane of the tyre and tangent to the maximum diameter of the tyre, such a representation corresponding to the plan development of the outer profile of the tread band.

[0063] The values of angles, and / or linear entities (distances, widths, lengths, etc.) and / or surfaces are deemed to refer to the tread pattern as defined above.

[0064] The term “average inclination” or “average angle” of a groove is used to indicate PIR478B

[0065] 8 the arithmetic average of the inclinations / angles arrangement of the portions that form the groove with respect to the equatorial plane of the tyre. For grooves with a curvilinear development, the average inclination or angle can be expressed as: where a(x) represents the angle of the groove at the longitudinal “height” x and L represents the extension of the groove.

[0066] The term “equatorial plane” of the tyre is used to indicate a plane perpendicular to the rotation axis of the tyre and that divides the tyre into two equal parts.

[0067] The term “axial development” of the tread pattern, of the tread band or of portions thereof, is used to indicate the development of the radially outermost profile of the tread band or of portions thereof in a cross-section of the tyre taken in a plane containing the rotation axis of the tyre.

[0068] The term “axial half-development” of the tread pattern, of the tread band or of portions thereof is used to indicate the development, from the equatorial plane and towards an axially outer end of the tyre, of the radially outermost profile of the tread band or of portions thereof in a cross section of the tyre taken in a plane containing the rotation axis of the tyre.

[0069] The term “curvature ratio” of the tyre is used to indicate the ratio between the distance of the radially highest point of the tread band from the maximum cord of the tyre, and the same maximum chord of the tyre, in a cross section of the tyre.

[0070] The term “maximum cord” or “maximum width of radial section”, is used to indicate the maximum width of the profile of the tyre, i.e. the dimension of the segment having the two axially outermost points of the profile of the tread band as extremities.

[0071] The term “annular portion”, “annular sub-portion” or “annular sector” is used to indicate a portion or sub-portion of tread band circumferentially extending for the entire tread band and of predetermined axial development.

[0072] The term “central annular portion” is used to indicate a tread portion circumferentially extending for the entire tread band and having an axial development defined by the distance between axially inner ends of transversal grooves formed in lateral annular portions of the tread band. PIR478B

[0073] 9

[0074] The distance of an annular portion of tread band from the equatorial plane or the distance between annular portions of tread band is axially evaluated by referring to the central plane parallel to the equatorial plane of the portion(s).

[0075] Unless specified otherwise, the term “extension” or “length” of a groove or of parts thereof is used to indicate the length of the groove or of a part thereof measured along the development thereof.

[0076] The term “rib” is used to indicate a solid portion of vulcanized elastomeric material that is located between consecutive grooves, for example axially or circumferentially consecutive grooves.

[0077] The term “directrix” of a groove or rib is used to indicate the line (straight, broken or curved) that represents the development of the groove or of the rib along the main direction thereof, similar to an axis of symmetry; it can also be seen as the location of the centres of all possible circles, tangent to the walls of the groove or to the edges of the rib.

[0078] The term “circumferential” or “longitudinal” direction is used to indicate a direction generically directed according to the direction of rotation of the tyre (and thus substantially parallel to the equatorial plane of the tyre), or in any case inclined with respect to the direction of rotation of the tyre by an angle lower than or equal to about 2°, preferably lower than or equal to about 1 .5°, more preferably lower than or equal to about 1 °.

[0079] The term “circumferential groove” or “circumferential rib” is used to indicate a groove or rib that extends in a substantially circumferential direction, i.e. along a direction that, in the circumferential development of the tread band (and therefore in the tread pattern), is parallel to the line defined by the equatorial plane of the tyre or inclined with respect to such a line by an angle lower than or equal to about 2°, preferably lower than or equal to about 1 .5°, more preferably lower than or equal to about 1 °.

[0080] The term “transversal groove” or “transversal rib” is used to indicate a groove or rib comprising at least one portion that, in the axial development of the tread band (and therefore in the tread pattern), extends along one or more directions inclined with respect to the equatorial plane of the tyre by an angle as defined in the present document.

[0081] With reference to the angle of the grooves or of the ribs of the tread band with respect to the equatorial plane of the tyre, such an angle is in particular deemed PIR478B

[0082] 10 for each point of the groove or of the rib as referring to the angle, comprised in an absolute value between 0° and 90°, formed by carrying out a rotation that, starting from the direction defined, in the tread pattern, by the equatorial plane or by a plane parallel to the equatorial plane, proceeds up to the direction tangent to the groove or rib passing through such a point.

[0083] The direction tangent to the groove passing through a certain point of the groove or of the rib is parallel to the directrix of the groove or of the rib as defined in the present document. In other words, the angle of the grooves, of the ribs or of portions thereof can be obtained from the angle of the directrix of the grooves, of the ribs or of portions thereof.

[0084] When the groove comprises several groove portions inclined with respect to one another, such a groove is defined as “transversal groove” if, in the axial development of the tread band (and therefore in the tread pattern), the groove extends along a respective direction inclined with respect to the equatorial plane of the tyre by an angle as defined in the present document.

[0085] When the groove comprises several groove sub-portions separated by solid parts of tread band, the latter have a length, measured along a directrix of the groove, not greater than 25%, preferably comprised between 2.5% and 25%, of the total length of the transversal grooves measured along said directrix.

[0086] The expression “substantially parallel to one another” with reference to the transversal grooves or to the transversal ribs or to parts thereof, is used to indicate that in any plane parallel to the equatorial plane of the tyre, the angle formed by the directrix of the groove or of the rib, or of a part thereof, with respect to the equatorial plane does not differ from the angle formed by the directrix of any other groove or rib, or of a part thereof, or it differs from such an angle by an angle equal to or less than about 5°, preferably equal to or less than about 3°, more preferably equal to or less than about 1 °.

[0087] The term “width” of the grooves is used to indicate the distance between opposite edges thereof. Such a dimension can for example be defined by the diameter of a circle tangent to the opposite edges of the grooves and inscribed in the grooves themselves.

[0088] The term “width” of the ribs defined between consecutive grooves is used to indicate the distance between facing edges of the aforementioned grooves in the circumferential direction and in the measuring portion. Such a dimension can for PIR478B

[0089] 11 example be defined by the diameter of a circle tangent to the facing edges of consecutive grooves and inscribed between said grooves.

[0090] The term “pitch” of the tyre is used to indicate the group of grooves and solid parts arranged so as to form a portion of pattern that repeats on the tread band, substantially equal to itself and without interruption along the circumferential development of the tread band. Along the circumferential development of the tread band, the pitches can have different circumferential lengths.

[0091] The term “substantially curvilinear” course of a groove is used to indicate a course with substantial continuity of the derivative of the curve that represents the course itself. Typically, this is obtained with a course without sharp points. The present definition also includes cases in which a groove is formed by or comprises a succession of short straight sections, provided that the difference in the angular arrangement between such sections is not too large (for example equal to or greater than about 25°).

[0092] The term “ground contacting area” of the tyre is used to indicate the portion of tyre in contact with the road surface when the tyre is mounted on a wheel rim and a predetermined vertical load is exerted on the tyre.

[0093] In the present description and in the following claims, all numerical entities indicating amounts, parameters, percentages and so forth are to be understood as being preceded in all instances by the term “about” unless indicated otherwise. Moreover, all the ranges of numerical entities include all the possible combinations of the maximum and minimum numerical values and all the possible intermediate ranges, in addition to those specifically indicated hereinbelow.

[0094] Unless otherwise indicated, all ranges of numerical quantities also include maximum and minimum numerical values.

[0095] The tyre of the present invention can comprise one or more of the features indicated hereinafter, taken singularly from one another or in combination with one another.

[0096] In a preferred embodiment, the tyre of the invention is a tyre intended to equip two-wheeled motorcycles belonging to the so-called “Supersport” and / or “Hypersport” segment, having a high displacement (for example 600 cm3or more), and / or high power (for example 200 horsepower or more), used both on road and on track. PIR478B

[0097] 12

[0098] In recent times, it has in fact been observed that there is a tendency to introduce on the market motorcycles belonging to the so-called “Supersport” and / or “Hypersport” segment, having a high power both for road use and for track use and having a displacement of 1000 cm3and more, with powers of 200 horsepower or even more.

[0099] In a further preferred embodiment, the tyre of the invention is a tyre intended to equip two-wheeled motorcycles belonging to the so-called “miniGP” segment, i.e. motorcycles of smaller weight and displacement and used for recreational and / or training purposes on dedicated tracks.

[0100] In recent times, it has in fact been observed that there is a tendency to introduce on the market motorcycles belonging to the so-called “miniGP” segment, i.e. motorcycles of lower weight (for example 60 to 90 kg), displacement (for example 150 to 190 cc) and power (15-25 horsepower), and used for recreational and / or training purposes on track.

[0101] Preferably, the transversal grooves formed in the lateral annular portions of the tread band have an axial extension comprised between 39% and 49%, more preferably between 44% and 49%, of the axial half-development of the tread band

[0102] In this way, it is advantageously possible to achieve optimal results in terms of improvement of the homogeneity of the driving and grip performance on wet or humid ground and / or in cold weather or in non-optimal road surface conditions of the tyre as the camber angle of the tyre changes. All this, without jeopardizing the water drainage performance under the ground contacting area of the tyre and the wear resistance of the tyre itself.

[0103] Preferably, the aforementioned first lateral annular sub-portion of the lateral annular portions of the tread band axially extends along 20%-32% of the axial development of the tread band.

[0104] In this way, it is advantageously possible to optimize the technical effect of ensuring an adequate axial development of the area of the tread band affected by the transition between travel along a straight course and cornering at limited camber angles.

[0105] Preferably, the first annular sector axially extends along 7%-32% of the axial development of the tread band.

[0106] Preferably, the first directrix of the first groove portion of the transversal grooves PIR478B

[0107] 13 forms with the equatorial plane of the tyre an angle having a minimum value comprised between 20° and 30° at an end of the first groove portion proximal to the equatorial plane.

[0108] Preferably, the second transversal rib portion has a substantially constant width comprised between 6% and 12% of the axial half-development of the tread band.

[0109] Preferably, said transversal ribs are substantially parallel to one another substantially for the entire axial extension thereof.

[0110] Preferably, said transversal ribs are substantially continuous for the entire axial extension thereof.

[0111] In particular, the number of the transversal ribs defined between circumferentially consecutive transversal grooves does not vary in the axial direction going from the first to the second transversal annular sub-portions of the tread band.

[0112] Preferably, said tread band comprises, in a plan development thereof, a central annular portion arranged astride of the equatorial plane of the tyre.

[0113] Preferably, said first annular sector of the first lateral annular sub-portion is axially arranged outside and adjacent to said central annular portion.

[0114] Preferably, the central annular portion of the tread band axially extends along 1 %-22% of the axial development of the tread band.

[0115] If there are no circumferential grooves in the central annular portion of the tread band, the central annular portion of the tread band axially extends along 1 %-4.5% of the axial development of the tread band.

[0116] If and as will be illustrated below in the central annular portion of the tread band there are one or more circumferential grooves, the central annular portion of the tread band axially extends along 12%-22% of the axial development of the tread band.

[0117] Thanks to these characteristics of axial extension of the central annular portion of the tread band, it is advantageously possible to achieve optimal performance of an improved thrust under braking or acceleration of the tyre on a wet or humid surface and / or in cold weather conditions or conditions of non-optimal road surface.

[0118] Preferably, each of said lateral annular portions of the tread band axially extends PIR478B

[0119] 14 along 38% -49.5% of the axial development of the tread band.

[0120] In preferred embodiments and if no circumferential grooves are present in the central annular portion of the tread band, each of said lateral annular portions of the tread band axially extends along 47.75% -49.5% of the axial development of the tread band.

[0121] In preferred embodiments and if circumferential grooves are present in the central annular portion of the tread band, each of said lateral annular portions of the tread band axially extends along 38%-46% of the axial development of the tread band.

[0122] In this way, it is advantageously possible to optimize the technical effect of ensuring, in all travel conditions of the motorcycle, both adequate water drainage and a continuity of interaction between the tyre and the road surface as the camber angle changes, allowing to increase the grip with the road surface and, in the case of a front tyre, to improve the braking thrust of the tyre.

[0123] Preferably, the second lateral annular sub-portion of the lateral annular portions of the tread band axially extends along 10%-32%, more preferably along 20%- 28%, of the axial development of the tread band.

[0124] In this way, it is advantageously possible to achieve optimal water drainage performance, drivability, in particular contact feeling, and improvement of the braking or acceleration thrust of the tyre on wet or humid surface and / or in cold weather conditions or conditions of non-optimal road surface at high camber angles.

[0125] Preferably, the tread band comprises a circumferential solid portion in said central annular portion axially arranged between axially inner ends of first groove portions proximal to the equatorial plane arranged on opposite sides with respect to the equatorial plane.

[0126] Preferably, the aforementioned circumferential solid portion of tread band is arranged astride of the equatorial plane of the tyre.

[0127] Preferably, the aforementioned circumferential solid portion of tread band is integral with the first transversal rib portion of said transversal ribs.

[0128] Preferably, the aforementioned circumferential solid portion of tread band has an axial extension comprised between 2% and 9%, of the axial development of the tread band. PIR478B

[0129] 15

[0130] In this way, it is advantageously possible to ensure an adequate axial stiffness of the tyre, i.e. an adequate stability and precision when driving along a straight course.

[0131] Preferably, said first transversal rib portion has a minimum width, measured at an axially inner end thereof, comprised between 3% and 25%, more preferably between 4% and 6%, of the axial half-development of the tread band.

[0132] Preferably, the first transversal rib portion has a maximum width, measured at an axially outer end thereof, comprised between 5% and 55% of the axial halfdevelopment of the tread band.

[0133] More preferably, the first transversal rib portion has a maximum width, measured at an axially outer end thereof, comprised between 20% and 55%, even more preferably 25% and 40%, of the axial half-development of the tread band in the case of tyres approved for road use.

[0134] More preferably, the first transversal rib portion has a maximum width, measured at an axially outer end thereof, comprised between 6% and 15%, even more preferably 8% and 12%, of the axial half-development of the tread band in the case of tyres approved for use on track.

[0135] Preferably, the first transversal rib portion has a width, measured at an axially outer end of the first annular sector, comprised between 4% and 35% of the axial half-development of the tread band.

[0136] More preferably, the first transversal rib portion has a width, measured at an axially outer end of the first annular sector, comprised between 13% and 35%, even more preferably 15% and 25%, of the axial half-development of the tread band in the case of tyres approved for road use.

[0137] More preferably, the first transversal rib portion has a width, measured at an axially outer end of the first annular sector, comprised between 4% and 11 %, even more preferably 5.5% and 9%, of the axial half-development of the tread band in the case of tyres approved for use on track.

[0138] Preferably, a ratio between a width of said first transversal rib portion measured at an axially outer end of the first annular sector and a minimum width measured at an axially inner end of said first transversal rib portion is comprised between 1.3 and 3.7. PIR478B

[0139] 16

[0140] In this way, it is advantageously possible to maintain essentially constant the shear elastic characteristics of the tread thereby optimising the aforementioned gradualness in the response to the stresses of the elastomeric material that constitutes the ribs optimising the driving and feeling characteristics of the tyre as the camber angle varies.

[0141] Preferably, the aforementioned first directrix of the first groove portion forms with the equatorial plane of the tyre an increasing angle, more preferably progressively increasing, moving away from the equatorial plane of the tyre between said minimum value and said maximum value.

[0142] In this way, it is advantageously possible to optimize the aforementioned gradualness in the response to the stresses of the elastomeric material that constitutes the ribs optimizing the driving and feeling characteristics of the tyre as the camber angle varies, allowing in particular to have limited and monotonous variations of the tyre stiffness as the camber angle varies, both when entering and exiting a bend.

[0143] Preferably, in said first annular sector defined in the first lateral annular subportion of the tread band and moving away from the equatorial plane, the width of the first transversal rib portion increases not more than 70%, more preferably, increases from 1 % to 40%, even more preferably from 3% to 40%, even more preferably from 3% to 35%, passing from a given annular area to an axially adjacent annular area of said reference system defined in the first lateral annular sub-portion of the tread band.

[0144] More preferably, in said first annular sector the first transversal rib portion has a width, as defined above, progressively increasing moving away from the equatorial plane between an end of the first transversal rib portion proximal to the equatorial plane and an end of the first transversal rib portion distal with respect to the equatorial plane.

[0145] Thanks to the aforementioned characteristics, it is advantageously possible to further optimize the improvement of the braking or acceleration thrust of the tyre thanks to a “continuity” of shape and sizes in the circumferential direction of the ribs under the ground contacting area of the tyre as the camber angle increases from the conditions of slight bend to full bend of the tyre (i.e. entering or exiting a bend).

[0146] Preferably, the first groove portion of the transversal grooves has a substantially PIR478B

[0147] 17 curvilinear course forming a concavity circumferentially oriented in the same direction or in opposite direction with respect to the rolling direction of the tyre.

[0148] In this way, it is advantageously possible to mitigate the effects of the performance degradation of the tyre due to wear.

[0149] Preferably, the first groove portion of the transversal grooves having a substantially curvilinear course is arranged at an average angle comprised between the aforementioned values 15° and 50°, more preferably between 20° and 30° indicated above for the first direction of the first groove portion, with respect to the equatorial plane of the tyre.

[0150] In this way, it is advantageously possible to mitigate the effects of the performance degradation of the tyre due to wear.

[0151] Preferably, the aforementioned first transversal groove portion is at least partially tapered in a direction from a shoulder portion of the tyre towards the equatorial plane of the tyre.

[0152] In this way, it is advantageously possible to give adequate continuity to the tread pattern between axially inner and axially outer portions of the first lateral annular sub-portion thereof in particular in the case of transversal grooves comprising portions forming therebetween a circumferentially oriented vertex or in the case of curvilinear transversal grooves.

[0153] Preferably, the aforementioned first transversal groove portion has a minimum width, measured at an axially inner end thereof, comprised between 2.5% and 6.5%, more preferably between 3% and 5%, of an axial half-development of the tread band.

[0154] In this way, it is advantageously possible to both optimize the water drainage characteristics under the ground contacting area of the tyre, and to have an optimal compromise between rib mobility and water drainage characteristics in the transition between travel along a straight course and cornering at low camber angles.

[0155] Preferably, the aforementioned first transversal groove portion has a maximum width, measured at an axially outer end thereof, comprised between 3.5% and 9%, more preferably between 5% and 8%, of an axial half-development of the tread band. PIR478B

[0156] 18

[0157] In this way, it is advantageously possible to optimize the water drainage characteristics under the ground contacting area of the tyre in cornering conditions at high camber angles.

[0158] Preferably, in said first lateral annular sub-portion a ratio between a maximum width of said first transversal groove portion measured at an axially outer end of said first transversal groove portion and a minimum width measured at an axially inner end of said first transversal groove portion is comprised between 1 .2 and 2.

[0159] In this way, it is advantageously possible to optimize the shear stiffness of the of the tread band portion present under the ground contacting area of the tyre, limiting possible phenomena of local deformability that can worsen water drainage and the continuity characteristics of the tread pattern.

[0160] Preferably, the aforementioned second transversal groove portion has a width comprised between 2% and 10%, more preferably between 3.5% and 6% of an axial half-development of the tread band.

[0161] In this way, it is advantageously possible to optimize the water drainage characteristics under the ground contacting area of the tyre in cornering conditions and in particular at high camber angles, so-called “high bend”.

[0162] Preferably, the aforementioned first transversal groove portion comprises at least two substantially rectilinear sub-portions forming therebetween a vertex that is circumferentially oriented in the same direction or in an opposite direction with respect to the rolling direction of the tyre.

[0163] In this way, it is advantageously possible to mitigate the effects of performance degradation of the tyre due to wear.

[0164] Preferably, the aforementioned rectilinear sub-portions of the first transversal groove portion form therebetween a vertex angle comprised between 135° and 179°.

[0165] In other words, the second axially outer portion of the transversal grooves forms an angle comprised between 1 ° and 15° with the first axially inner portion.

[0166] In this way, it is advantageously possible to mitigate the effects of performance degradation of the tyre due to wear.

[0167] In a preferred embodiment, the tread band comprises a plurality of transversal grooves formed in the lateral annular portions of the tread band comprising a PIR478B

[0168] 19 plurality of groove sub-portions separated by a solid portion of tread band.

[0169] In this way, it is advantageously possible to modulate the shear stiffness of the tread band portion present under the ground contacting area of the tyre.

[0170] Preferably, said solid part of tread band has a length, measured along a directrix of said transversal grooves, not greater than 25%, more preferably comprised between 2.5% and 25%, of the total length of the transversal grooves measured along said directrix.

[0171] In this way, it is advantageously possible to optimize the shear stiffness of the tread band portion present under the ground contacting area of the tyre, limiting possible phenomena of local deformability that can worsen water drainage and the continuity characteristics of the tread pattern.

[0172] Preferably, said groove sub-portions of the transversal grooves formed in the lateral annular portions of the tread band have a length, measured along the directrix of said transversal grooves, comprised between 20% and 75% of the total length of the transversal grooves.

[0173] In this way, it is advantageously possible to optimize the shear stiffness of the tread band portion present under the ground contacting area of the tyre, limiting possible phenomena of local deformability that can worsen water drainage and the continuity characteristics of the tread pattern.

[0174] In a preferred embodiment, the tread band comprises at least one longitudinal groove formed in the central annular portion of the tread band.

[0175] Preferably, said at least one longitudinal groove is formed at, even more preferably astride of, the equatorial plane of the tyre.

[0176] Preferably, the tread band comprises at least two longitudinal grooves formed in the central annular portion arranged on opposite sides with respect to the equatorial plane of the tyre.

[0177] Preferably, the aforementioned at least two longitudinal grooves formed in the central annular portion of the tread band are symmetrically arranged on opposite sides with respect to the equatorial plane of the tyre.

[0178] Preferably, said at least one or said at least two longitudinal grooves have an axial extension comprised between 1 % and 8%, of the axial half-development of the tread band. PIR478B

[0179] 20

[0180] In this way, it is advantageously possible to have a tread pattern that combines adequate water drainage under the ground contacting area of the tyre and traction characteristics along a straight course.

[0181] Preferably, the aforementioned at least two longitudinal grooves formed in the central annular portion of the tread band and arranged on opposite sides with respect to the equatorial plane of the tyre define a circumferential rib arranged astride of the equatorial plane of the tyre.

[0182] Preferably, the tread band comprises four longitudinal grooves, formed in the central annular portion thereof.

[0183] Preferably, the aforementioned four longitudinal grooves define a circumferential rib arranged astride of the equatorial plane of the tyre.

[0184] Preferably, said four longitudinal grooves are symmetrically arranged on opposite sides with respect to the equatorial plane of the tyre.

[0185] Preferably, said four longitudinal grooves are arranged in two pairs symmetrically positioned on opposite sides with respect to the equatorial plane of the tyre.

[0186] Preferably, the aforementioned circumferential rib arranged astride of the equatorial plane of the tyre has an axial extension comprised between 10% and 16%, of the axial half-development of the tread band if two or more circumferential grooves are present in the central annular portion of the tread band.

[0187] In this way, it is advantageously possible to ensure an adequate axial stiffness of the tyre, i.e. adequate stability and precision when driving along a straight course.

[0188] Preferably, the tread band comprises a longitudinal groove formed at, more preferably astride of, the equatorial plane of the tyre and two further longitudinal grooves formed in the central annular portion and preferably symmetrically arranged on opposite sides with respect to said longitudinal groove formed at the equatorial plane of the tyre.

[0189] In this way, it is advantageously possible to achieve an optimal performance in terms of water drainage under the ground contacting area of the tyre in combination with adequate axial stiffness of the tyre, i.e. adequate stability and precision when driving along a straight course, imparted by the circumferential ribs axially defined between the aforementioned longitudinal grooves.

[0190] Preferably, an axially inner end of said first transversal groove portion is arranged PIR478B

[0191] 21 at a predetermined distance from said at least one longitudinal groove, or from an axially outermost longitudinal groove of said at least two longitudinal grooves.

[0192] In this preferred embodiment, a circumferential solid portion of tread band is thus formed which is axially arranged between the axially inner end of the first transversal groove portion and the aforementioned at least one longitudinal groove, or the aforementioned axially outermost longitudinal groove of said at least two longitudinal grooves.

[0193] Preferably, the aforementioned circumferential solid portion of tread band is integral with said first transversal rib portion.

[0194] Preferably, the distance between the axially inner end of the transversal grooves formed in the lateral annular portions of the tread band and i) said at least one longitudinal groove formed in the central annular portion of the tread band, or ii) an axially outermost longitudinal groove of said at least two longitudinal grooves formed in the central annular portion of the tread band, is comprised between 1 % and 9% of the axial half-development of the tread band.

[0195] Correspondingly, therefore, the circumferential solid portion of tread band axially arranged between the axially outermost longitudinal groove and the axially inner end of the transversal grooves has an axial extension, identifiable with the aforementioned distance, comprised between 1 % and 9%, of the axial halfdevelopment of the tread band.

[0196] In this way, it is advantageously possible to optimise the technical effect of ensuring a continuity of interaction between the tyre and the road surface in all the driving conditions when the camber angle varies, allowing to increase the grip with the road surface and, in the case of a front tyre, to improve the handling and feeling characteristics of the tyre at low camber angles.

[0197] In a preferred embodiment, the second transversal rib portion of the transversal ribs lying in the second lateral annular sub-portion of the tread band has a width comprised between 6% and 15% of the axial half-development of the tread band in the case of racing tyres (for example miniGP, Hypersport or Superbike) approved for use on track in wet road conditions called “full rain”.

[0198] In a preferred embodiment, the second transversal rib portion of the transversal PIR478B

[0199] 22 ribs lying in the second lateral annular sub-portion of the tread band has a width comprised between 22% and 57% of the axial half-development of the tread band in the case of racing tyres (for example miniGP, Hypersport or Superbike) approved for use on track in wet road conditions called “wet”.

[0200] In a further preferred embodiment, the second transversal rib portion of the transversal ribs lying in the second lateral annular sub-portion of the tread band has a width comprised between 22% and 55%, more preferably comprised between 25% and 40%, of the axial half-development of the tread band in the case of tyres approved for road use.

[0201] In this way, it is advantageously possible to optimise the technical effect of ensuring an adequate interaction between the tyre and the road surface in all travel conditions of the motorcycle, allowing to increase the grip with the latter and to improve, in the case of a front tyre, the braking thrust of the tyre.

[0202] In this way, it is advantageously possible to exploit the geometry of the pattern both for tyres for track use in wet conditions and for road use.

[0203] Preferably, the tyre is a tyre for a front motorcycle wheel.

[0204] In this case, the tyre preferably has a transversal curvature ratio greater than or equal to 0.20, more preferably greater than or equal to 0.25, even more preferably greater than or equal to 0.30.

[0205] The tyre for a front motorcycle wheel preferably has a transversal curvature ratio lower than or equal to 0.50, preferably lower than or equal to 0.45.

[0206] Preferably, the tyre is a tyre for a rear motorcycle wheel.

[0207] In this case, the tyre preferably has a transversal curvature ratio greater than or equal to 0.20, more preferably greater than or equal to 0.25, even more preferably greater than or equal to 0.29.

[0208] The tyre for a rear motorcycle wheel preferably has a transversal curvature ratio lower than or equal to 0.40, preferably lower than or equal to 0.35.

[0209] In a preferred embodiment, the tyre can have a nominal fitting diameter comprised between 10” and 18”.

[0210] In this way, the tyre advantageously allows to equip a wheel, for example the rear wheel, of motorcycles belonging to the so-called “Supersport” and / or “Hypersport” PIR478B

[0211] 23 segment, having a high displacement (for example 600 cm3or more), and / or high power (for example 200 horsepower or more), used both on road and on track.

[0212] In a further preferred embodiment, the tyre can have a nominal fitting diameter comprised between 10” and 12”.

[0213] In this way, the tyre advantageously allows to equip a wheel, for example the rear wheel, of motorcycles belonging to the so-called “miniGP” segment, i.e. motorcycles having more limited weight (for example from 60 to 90 kg), power (for example 15-25 horsepower) and displacement (for example from 150 to 190 cc) and used for recreational and / or training purposes on dedicated circuits.

[0214] Brief Description of the Figures

[0215] Additional features and advantages of the invention will be better apparent from the following description of some preferred embodiments thereof, made below, for illustrative and not limiting purposes, with reference to the attached drawings.

[0216] Such drawings are schematic and are not to scale.

[0217] In the drawings:

[0218] - Figure 1 shows a perspective view of a front motorcycle tyre according to a preferred embodiment of the invention;

[0219] - Figure 2 is an enlarged view of a cross section of the tyre of Figure 1 ;

[0220] - Figure 3 is a schematic view of a plan development of a portion of the tread band of the tyre of Figure 1 ;

[0221] - Figures 4-9 are as many schematic views of a plan development of a portion of alternative preferred embodiments of the tread pattern of the front tyre of Figure 1 ;

[0222] - Figures 10-13 show as many graphs illustrating the course of the width of the transversal ribs formed in the tread band as a function of the distance from the equatorial plane within the axial half-development of the tread band for the preferred embodiments of the tyre illustrated in Figures 3 and 8 and, respectively, 6 and 9.

[0223] Detailed description of embodiments

[0224] In Figures 1 -3, a tyre for motorcycle wheels according to a first preferred PIR478B

[0225] 24 embodiment of the present invention is generally indicated at 1 .

[0226] Preferably, the tyre 1 is a front tyre having a nominal fitting diameter comprised between 10” and 18”, more preferably intended to be used on a wheel of a motorcycle for a supersports motorbike having large displacement, for example 600cc.

[0227] An equatorial plane X-X and a rotation axis Z are defined in the tyre 1 (see Figure 2).

[0228] A circumferential direction (indicated in Figures 1 and 3 with the arrow F oriented in the rotation direction of the tyre 1 ) and an axial direction perpendicular to the equatorial plane X-X are also defined.

[0229] The tyre 1 comprises a carcass structure 2 having a central crown portion 3 including at least one carcass ply 4, described hereinafter in greater detail.

[0230] The carcass structure 2 is preferably coated, on the inner walls thereof, by a sealing layer 5, or so-called “liner”, essentially consisting of an airtight layer of elastomeric material, adapted to impart a hermetic seal to the tyre itself once inflated.

[0231] The carcass ply 4 has its axially opposite lateral edges 4a facing respective annular reinforcing structures 6 intended to hold the tyre 1 on a corresponding mounting rim. The annular reinforcing structures 6 are typically called “bead cores”.

[0232] The outer perimetral edge of the bead cores 6 has a tapered elastomeric filler 7 applied thereon, which occupies the space defined between the carcass ply 4 and the corresponding turned-up side edge 4a of the carcass ply 4.

[0233] In an alternative embodiment, not illustrated, the carcass ply has the opposite side edges thereof associated without a turn-up to special annular reinforcing structures provided with two metallic annular inserts. In this case, a filler made of elastomeric material can be arranged at an axially outer position with respect to the first annular insert. The second annular insert is, on the other hand, arranged at an axially outer position with respect to the end of the carcass ply. Finally, at an axially outer position with respect to said second annular insert, and not necessarily in contact therewith, a further filler may be provided that completes the configuration of the annular reinforcing structure. PIR478B

[0234] 25

[0235] The area of the tyre comprising the bead core 6 and the filling 7 forms the so- called “bead”, globally indicated in figure 1 with 8, intended for anchoring the tyre on a corresponding mounting rim, not illustrated.

[0236] A belt structure 9, also described in greater detail hereinafter, is provided at a radially outer position with respect to the aforementioned carcass structure 2.

[0237] A tread band 10, by means of which the contact of the tyre 1 with the ground takes place, is provided at a radially outer position with respect to the belt structure 9.

[0238] The tyre 1 can also comprise a pair of sidewalls 11 laterally applied to the carcass structure 2 on axially opposite sides with respect to the equatorial plane X-X. The sidewalls 11 extend from the tread band 10 to the bead 8 of the tyre 1 .

[0239] The tyre 1 of the present invention is distinguished by a high transversal curvature.

[0240] The transversal curvature of a tyre is defined by the particular value of the curvature ratio or “arrow” of the tyre. With reference to Figure 2 and in accordance with the definition given above, the curvature ratio is the ratio between the distance f of the radially outermost point P (or top) of the tread band 10 from the line b-b passing through the ends E of the tread band 10, measured along the equatorial plane X-X, and the distance wt between the ends E of the tread band 10. In all cases, even if the ends of the tread band are not easily identifiable, for example due to the lack of a precise reference such as for example the ends indicated in figure 2 with E, the measurement of the maximum cord, or maximum width of radial section, of the tyre 1 , may be taken as distance wt.

[0241] The tyre 1 of the present invention preferably has a transversal curvature ratio of 0.20, more preferably greater than or equal to 0.25, even more preferably greater than or equal to 0.30, and preferably less than or equal to 0.50, more preferably less than or equal to 0.45.

[0242] As to the sidewalls 11 , the tyre 1 of the present invention is preferably a tyre with low profile sidewalls, i.e. in which the ratio between the distance f and the height H, measured on the equatorial plane X-X between the top of the tread band 10 and the fitting diameter, identified by the reference line LR passing through the beads 8 of the tyre 1 , is lower than 0.65, more preferably lower than 0.6, for example equal to 0.55.

[0243] The carcass ply 4 is preferably made of elastomeric material and comprises a PIR478B

[0244] 26 plurality of reinforcing elements (not illustrated) arranged parallel to one another and perpendicular to the equatorial plane.

[0245] The reinforcing elements included in the carcass ply 4 preferably comprise textile cords selected among those usually adopted in the manufacture of carcasses for tyres, for example nylon, rayon, PET, PEN, Lyocell, each cord comprising elementary wires each having a diameter comprised between 0.35 mm and 1.5 mm, or metallic cords made of steel with an elementary wire of diameter comprised between 0.10 mm and 0.5 mm.

[0246] The belt structure 9 preferably comprises rubber-coated cords, not better illustrated in figure 2, arranged substantially parallel and side-by-side in the axial direction on the crown portion 3 of the carcass structure 2, to form a plurality of coils. These coils are substantially oriented according to the rolling direction of the tyre 1 (in particular with an angle comprised between 0° and 5° with respect to the equatorial plane X-X), such a direction being usually called “zero degrees”. The aforementioned coils preferably extend over the entire crown portion 3 of the carcass structure 2.

[0247] Preferably, the belt structure 9 comprises windings of a single cord, or of a band of rubber-coated fabric comprising side-by-side cords, preferably up to five cords, spirally wound from one end to the other on the crown portion 3 of the carcass structure 2.

[0248] Preferably, such cords can be made of steel wires having a high carbon content (HT), i.e. steel wires with a carbon content greater than 0.9%.

[0249] Alternatively, the belt structure 9 can comprise at least two radially juxtaposed layers, each consisting of elastomeric material reinforced with cords arranged parallel to each other. The layers are arranged so that the cords of the first belt layer are oriented obliquely with respect to the equatorial plane of the tyre, whereas the cords of the second layer also have an oblique orientation, but symmetrically crossed with respect to the cords of the first layer, to form the so- called “crossed belt”.

[0250] In this case, generally, the cords of the belt structure 9 are generally textile cords, for example textile cords made of synthetic fibre, for example nylon, rayon, PEN, PET, preferably of synthetic fiber having a high modulus, in particular synthetic aramid fiber (aromatic polyamide). Alternatively, it is possible to use hybrid cords comprising at least one low modulus wire, i.e. with a modulus not greater than 15 PIR478B

[0251] 27

[0252] GPa (for example made of nylon or rayon), interwoven with at least one high modulus wire (for example aramid fiber - AR, aromatic polyamide), i.e. with a modulus not less than 25 GPa.

[0253] For aramid fibers (AR) the elastic modulus is evaluated according to BISFA - Testing methods for para-aramid fibre yams, 2002 edition, Determination of the linear density - Chapter 6, Determination of the tensile properties - Chapter 7 - Test procedure - Paragraph 7.5 - with procedure with initial pretensioning.

[0254] For the other fibers (nylon, rayon, etc.) the elastic modulus is evaluated according to: BISFA - Testing methods for viscose, cupro, acetate, triacetate and lyocell filament yams - 2007 edition, Determination of tensile properties - Chapter 7 - Tensile test conditions: oven dry test - Table 7.1 - Test procedure - Paragraph 7.5 - With oven dry test on relaxed samples - Subparagraph 7.5.2.4.

[0255] In both cases, the cords of the belt structure 9 are textile or metallic cords. Preferably, such cords are made of steel wires having a high carbon content (HT), i.e. steel wires with a carbon content greater than 0.9%. If textile cords are used, these can be made of a synthetic fiber, for example nylon, rayon, PEN, PET, preferably synthetic fiber having a high modulus, in particular synthetic aramid fiber (aromatic polyamides).

[0256] Preferably, the belt structure 9 may comprise a support layer, not better illustrated in figure 2, substantially consisting of a sheet of elastomeric material arranged between the layer of cords and the carcass ply 4 and on which the coils are wound. Said support layer preferably extends over a surface having an axial extension substantially corresponding to the surface on which the coils develop. Alternatively, the support layer can extend over a surface smaller than the development surface of the coils, for example only over opposite lateral portions of the belt structure 9.

[0257] In a further embodiment, also not illustrated, an additional layer of elastomeric material is arranged between the belt structure 9 and the tread band 10. Such a layer preferably extends over a surface corresponding to the development surface of the belt structure 9. Alternatively, the aforementioned additional layer can extend over a surface smaller than the development surface of the belt structure 9, for example only over opposite lateral portions of the belt structure 9.

[0258] In a preferred embodiment of the tyre 1 of the present invention, at least one of the support layer interposed between the cord layer of the belt structure 9 and PIR478B

[0259] 28 the carcass ply 4 and the aforementioned additional layer arranged between the belt structure 9 and the tread band 10 comprises short aramid fibres, for example made of Kevlar®, dispersed in the elastomeric material.

[0260] The tread band 10 has a tread pattern defined by a plurality of grooves formed on the outer surface of the tread band 10 by means of a molding operation carried out simultaneously with the vulcanization of the tyre 1 .

[0261] Figures 1 -3 show, as an example, a first preferred embodiment of a tread pattern that allows to achieve the desired characteristics of improved constancy in drainage, contact feeling and braking thrust on a wet or cold road surface when shifting from travel along a straight course to travel conditions with slight bend by varying the camber angle of the tyre 1 , keeping at the same time the wear characteristics thereof substantially unchanged.

[0262] In the present description and in the following claims, all the quantities of the elements of the tread band 10 are indicated and are deemed to be measured with reference to the plan development of the tread band itself.

[0263] The tread pattern of the tyre 1 comprises a modulus T repeated along a circumferential direction of the tyre 1 .

[0264] In the tyre 1 of the invention the modulus T corresponds to the portion of tread band 10 that, in the plan development illustrated in Figure 3, is circumferentially delimited by the two broken lines ti and t2.

[0265] As better illustrated in Figure 3, in which all the quantities - as indicated above - are measured in the plan development of the tread band 10, the modulus T has a circumferential length, indicated with C1 , and an axial development equal to the axial development L of the tread band 10.

[0266] In the preferred embodiment illustrated in Figures 1-3, the tread band 10 of the tyre 1 comprises a central annular portion L1 arranged astride of the equatorial plane X-X of the tyre 1 .

[0267] Preferably, the central annular portion L1 of the tread band 10 transversally extends along 1 %-4.5%, of the axial development L of the tread band 10.

[0268] In the preferred embodiment illustrated in Figures 1-3, the tread band 10 of the tyre 1 also comprises two lateral annular portions L2, L3 arranged on opposite sides of the central annular portion L1 with respect to the equatorial plane X-X of PIR478B

[0269] 29 the tyre 1 .

[0270] Preferably, the lateral annular portions L2, L3 of the tread band 10 extend axially along 38% -49.5%, preferably along 47.75% -49.5%, more preferably along 38%- 46%, of the axial development L of the tread band 10.

[0271] Each of the lateral annular portions L2, L3 comprises a first lateral annular subportion L2’, L3’, proximal with respect to the equatorial plane X-X, and a second lateral annular sub-portion L2”, L3”, distal with respect to the equatorial plane X- X.

[0272] Preferably, the first lateral annular sub-portion L2’, L3’ of the lateral annular portions L2, L3 axially extends along 7%-40%, preferably along 20%-32% of the axial development L of the tread band 10.

[0273] Preferably, the first lateral annular sub-portion L2’, L3’ of the lateral annular portions L2, L3 of the tread band 10 comprises a first annular sector S proximal to the equatorial plane X-X.

[0274] In the preferred embodiment illustrated, the first annular sector S is arranged axially outside of and adjacent to the central annular portion L1 .

[0275] Preferably, the first annular sector S axially extends along 7%-32% of the axial development L of the tread band 10.

[0276] Preferably, the second lateral annular sub-portion L2” L3” of the lateral annular portions L2, L3 axially extends along 10%-32%, preferably along 20%-28%, of the axial development L of the tread band 10.

[0277] In each of the lateral annular portions L2, L3 of the tread band 10 a plurality of transversal grooves 12 is formed obliquely extending with respect to the equatorial plane X-X of the tyre 1 and having a directrix “g”, which represents the course thereof along the main direction thereof.

[0278] Preferably, the transversal grooves 12 have an axial extension equal to at least 30%, more preferably an axial extension comprised between 39% and 49%, even more preferably an axial extension comprised between 44% and 49%, of the axial half-development L / 2 of the tread band 10.

[0279] Preferably, the transversal grooves 12 comprise a first groove portion 12’ lying in the first lateral annular sub-portion L2’, L3’ and a second groove portion 12” lying in the second lateral annular sub-portion L2”, L3”. PIR478B

[0280] 30

[0281] Preferably, the first groove portion 12’ of the transversal grooves 12 has a substantially curvilinear course forming a concavity circumferentially oriented in the same direction with respect to the rolling direction F of the tyre 1 .

[0282] Preferably, the first groove portion 12’ of the transversal grooves 12 has a first directrix g’ forming with the equatorial plane X-X an angle alpha which increases moving away from the equatorial plane X-X between a minimum value alpha’a comprised between 15° and 50° at an end 12’a of the first groove portion 12’ proximal to the equatorial plane X-X and a maximum value alpha’b comprised between 50° and 80° at an end 12’b of the first groove portion 12’ distal with respect to the equatorial plane X-X.

[0283] Preferably, the first directrix g’ of the first groove portion 12’ forms with the equatorial plane X-X an angle alpha which increases, preferably progressively increasing, moving away from the equatorial plane X-X between said minimum value alpha’a and said maximum value alpha’b.

[0284] Preferably, the central annular portion L1 of the tread band 10 is axially delimited by the axially inner ends 12’a of the first groove portion 12’ of the transversal grooves 12 formed in the first lateral annular sub-portion L2’, L3’ of the tread band 10 on opposite sides of the equatorial plane X-X.

[0285] Preferably, the transversal grooves 12 are arranged according to a circumferential succession configured so as to form between the transversal grooves 12 a circumferential succession of transversal ribs 13 extending up to the axial ends of the tread band 10.

[0286] Preferably, the transversal ribs 13 comprise a first transversal rib portion 13’ lying in the first lateral annular sub-portion L2’, L3’ and a second transversal rib portion 13” lying in the second lateral annular sub-portion L2”, L3” of the tread band 10.

[0287] Preferably, in the first lateral annular sub-portion L2’, L3’ a reference system is defined comprising a plurality of axially adjacent annular areas A each having an axial extension equal to 3% of the axial development L of the tread band 10 (see Figure 3).

[0288] Preferably, in the first lateral annular sub-portion L2’, L3’ and therefore also in the first annular sector S, the first transversal rib portion 13’ has a width, defined by the diameter of a circle tangent to the facing edges of the first circumferentially consecutive groove portions 12’ and inscribed between said first groove portions 12’, which is increasing, preferably progressively, moving away from the PIR478B

[0289] 31 equatorial plane X-X between an axially inner end Si of the first annular sector S proximal to the equatorial plane X-X and an axially outer end Se of the first annular sector S distal with respect to the equatorial plane X-X.

[0290] The above circle, indicated by reference C, is illustrated by way of example in Figure 3 in three different positions axially spaced apart from each other.

[0291] Preferably, in the first lateral annular sub-portion L2’, L3’ and therefore also in the first annular sector S, the width of the first transversal rib portion 13’ moving away from the equatorial plane X-X increases passing from a given annular area A to an axially adjacent annular area A of said reference system.

[0292] Preferably, the width of the first transversal rib portion 13’, in said first annular sector S defined in the first lateral annular sub-portion L2’, L3’ and moving away from the equatorial plane X-X, increases not more than 70%, more preferably increases from 1 % to 40%, even more preferably from 3% to 40%, even more preferably from 3% to 35% passing from a given annular area A to an axially adjacent annular area A of said reference system.

[0293] Preferably, the second groove portion 12” of the transversal grooves 12 has a second directrix g” forming with the equatorial plane X-X a substantially constant angle alpha”a comprised between 50° and 80° at an end 12”a of the second groove portion 12” proximal to the equatorial plane X-X and an angle alpha”b comprised between 80° and 90°, with reference to the equatorial plane X-X or to a plane parallel to the equatorial plane X-X and passing through the axially outer end of the tread band 10, according to the definition reported above, at an end 12”b of the second groove portion 12” distal with respect to the equatorial plane X-X.

[0294] Preferably, the second transversal rib portion 13” has a substantially constant width comprised between 5% and 60%, more preferably between 6% and 12%, of the axial half-development L / 2 of the tread band 10.

[0295] Preferably, the transversal grooves 12 are circumferentially offset from each other by a predetermined distance O, preferably comprised between 0% and 50%, more preferably between 30% and 50% of the circumferential length C1 of the module T.

[0296] Preferably, the tread band 10 comprises a circumferential solid portion 14 in said central annular portion L1 axially arranged between the axially inner ends 12’a of the first groove portions 12’ proximal to the equatorial plane X-X arranged on PIR478B

[0297] 32 opposite sides with respect to the equatorial plane X-X itself.

[0298] In the preferred embodiment illustrated in figures 1 -3, therefore, the circumferential solid portion 14 of the tread band 10 is integral with the first transversal rib portion 13’ of the transversal ribs 13.

[0299] Preferably, the first transversal groove portion 12’ is at least partially tapered in a direction from a shoulder portion of the tyre 1 towards the equatorial plane X-X of the tyre 1 .

[0300] Preferably, the first transversal groove portion 12’ has a minimum width, measured at an axially inner end 12’a thereof, comprised between 2.5% and 6.5%, more preferably between 3% and 5%, of the axial half-development L / 2 of the tread band 10.

[0301] Preferably, the width of the first transversal groove portion 12’ measured at an axially outer end Se of the first annular sector S is comprised between 3% and 7%, more preferably between 4% and 6%, of the axial half-development L / 2 of the tread band 10.

[0302] Preferably, the first transversal groove portion 12’ has a maximum width, measured at an axially outer end 12’b thereof, comprised between 3.5% and 9%, more preferably between 5% and 8%, of the axial half-development L / 2 of the tread band 10.

[0303] Preferably, in the first lateral annular sub-portion L2’, L3’ of the tread band 10, the ratio between the maximum width of the first transversal groove portion 12’ measured at an axially outer end 12’b thereof and the minimum width of the first transversal groove portion 12’ measured at an axially inner end 12’a thereof is comprised between 1 ,2 and 2.

[0304] Preferably, in the first lateral annular sub-portion L2’, L3’ of the tread band 10, the ratio between a width of said first groove portion 12’ measured at an axially outer end Se of the first annular sector S and a minimum width measured at an axially inner end 12’a of said first groove portion 12’ is comprised between 1.1 and 1 .5.

[0305] Preferably, the transversal grooves 12 have a substantially curvilinear course forming a concavity circumferentially oriented in the same direction with respect to the rolling direction F of the tyre 1 . PIR478B

[0306] 33

[0307] Preferably, the first groove portion 12’ of the transversal grooves 12 having a substantially curvilinear course is arranged at an average angle of about 25° with respect to the equatorial plane X-X of the tyre 1 .

[0308] In this preferred embodiment, the first transversal rib portion 13’ also has a substantially curvilinear course, preferably at an average angle similar to that of the first groove portion 12’ of the transversal grooves 12.

[0309] Preferably, the first transversal rib portion 13’ formed in the first lateral annular sub-portion L2’, L3’ of the lateral annular portions L2, L3 of the tread band 10 is tapered in a direction from a shoulder portion of the tyre 1 towards the equatorial plane X-X of the tyre 1 .

[0310] Preferably, the first transversal rib portion 13’ has a minimum width, measured at an axially inner end 13’a thereof, comprised between 3% and 25%, more preferably between 4% and 6%, of the axial half-development L / 2 of the tread band 10.

[0311] Preferably, the first transversal rib portion 13’ has a width, measured at an axially outer end Se of the first annular sector S, comprised between 4% and 35% of the axial half-development L / 2 of the tread band 10.

[0312] More preferably, the first transversal rib portion 13’ has a width, measured at an axially outer end Se of the first annular sector S, comprised between 13% and 35%, even more preferably 15% and 25%, of the axial half-development L / 2 of the tread band 10 in the case of tyres approved for road use.

[0313] More preferably, the first transversal rib portion 13’ has a width, measured at an axially outer end Se of the first annular sector S, comprised between 4% and 11 %, even more preferably 5.5% and 9%, of the axial half-development L / 2 of the tread band 10 in the case of tyres approved for use on track.

[0314] Preferably, the first transversal rib portion 13’ has a maximum width, measured at an axially outer end 13’b thereof, comprised between 5% and 55% of the axial half-development L / 2 of the tread band 10.

[0315] More preferably, the first transversal rib portion 13’ has a maximum width, measured at an axially outer end 13’b thereof, comprised between 20% and 55%, even more preferably 25% and 40%, of the axial half-development of the tread band 10 in the case of tyres approved for road use. PIR478B

[0316] 34

[0317] More preferably, the first transversal rib portion 13’ has a maximum width, measured at an axially outer end 13’b thereof, comprised between 6% and 15%, even more preferably 8% and 12%, of the axial half-development of the tread band 10 in the case of tyres approved for use on track.

[0318] Preferably, a ratio between a width of said first transversal rib portion 13’ measured at an axially outer end Se of the first annular sector S and a minimum width measured at an axially inner end 13’a of the first transversal rib portion 13’ is comprised between 1 .3 and 3.7.

[0319] Preferably, the second transversal groove portion 12” has a width comprised between 2% and 10%, preferably between 3.5% and 6% of the axial halfdevelopment L / 2 of the tread band 10.

[0320] Preferably, the transversal grooves 12 are substantially parallel to each other substantially for the entire axial extension thereof.

[0321] Preferably, the transversal ribs 13 are substantially continuous for the entire axial extension thereof.

[0322] Preferably, the transversal ribs 13 are substantially parallel to one another substantially for the entire axial extension thereof.

[0323] Figure 10 illustrates the course of the width of the transversal ribs 13 formed in the tread band 10 as a function of the distance from the equatorial plane X-X within the axial half-development L / 2 of the tread band 10 with reference to a tyre 1 having a size of 120 / 70 R17.

[0324] In particular, in this figure, the absolute values in mm of the width of the transversal ribs 13 as a function of the % distance from the equatorial plane X-X of the tyre 1 are indicated in ordinate.

[0325] By way of example, the graph of figure 10 refers to the right half of the plan development of the tread band 10 of the tyre 1 of figure 3, with the left half having a mirror-like course.

[0326] As can be seen from the graph reported in figure 10, the width of the transversal ribs 13 gradually increases in the first annular sector S defined in the first lateral annular sub-portion (L2’ in this case) and moving away from the equatorial plane X-X.

[0327] In particular, in this specific example, in the first annular sector S the width of the PIR478B

[0328] 35 first transversal rib portion 13’ increases from 3% to 35% passing from a given annular area A to an axially adjacent annular area A of said reference system.

[0329] Conversely, the width of the transversal ribs 13 in the second lateral annular subportion L2” of the tread band 10 remains substantially constant moving away from the equatorial plane X-X of the tyre 1 .

[0330] With reference to figures 4-9 additional preferred embodiments of the tread pattern of the tyre 1 according to the invention will now be described.

[0331] In the following the description and in such figures, the elements of the tyre 1 structurally or functionally equivalent to those illustrated earlier with reference to figures 1-3 will be indicated with the same reference numbers and will not be described any further.

[0332] In the embodiment of Figure 4, a variant of the tread band 10 is illustrated in which the transversal grooves 12 formed in the lateral annular portions L2, L3 of the tread band 10 comprise:

[0333] - a first plurality of transversal grooves 12 having a substantially curvilinear course along their directrix g and are substantially continuous for the entire axial extension thereof; and

[0334] - a second plurality of transversal grooves 12A, 12B having a substantially curvilinear course along their directrix g and each comprising a plurality of subportions separated by solid parts 15A’ 15A” and 15B of tread band 10.

[0335] Preferably, the transversal grooves 12A, 12B of the aforementioned second plurality of transversal grooves 12 are circumferentially interposed between substantially continuous and circumferentially consecutive transversal grooves 12.

[0336] More preferably, the second plurality of transversal grooves 12A, 12B comprises:

[0337] - a first transversal groove 12A having a substantially curvilinear course along its own directrix gA and comprising three groove sub-portions 12A’, 12A” and 12A’”, separated by solid parts 15A’ and 15A” of tread band 10, and

[0338] - a second transversal groove 12B having a substantially curvilinear course along its own directrix gB and comprising two groove sub-portions 12B’ and 12B” separated by solid parts 15B of tread band 10. PIR478B

[0339] 36

[0340] Preferably, the transversal groove 12A and the transversal groove 12B are circumferentially consecutive to each other and form a set of grooves circumferentially interposed between substantially continuous and circumferentially consecutive transversal grooves 12.

[0341] Preferably, the solid parts 15A’ and 15A” and 15B have a length, measured along their directrix gA and gB not greater 25% preferably comprised between 2.5% and 25%, of the total length of the transversal grooves 12 measured along said directrix gA, gB.

[0342] In relation to this preferred embodiment, the total length of the transversal grooves 12A, 12B is meant to be measured as if they were substantially continuous for the entire axial extension thereof, i.e. devoid of the solid parts 15A’, 15A” and 15B.

[0343] Preferably, the curvature characteristics of the grooves 12A, 12B may be similar to those described above with reference to the preferred embodiment illustrated in figures 1-3.

[0344] In particular, the groove sub-portions 12A’ and 12B’ have a geometric configuration and curvature characteristics similar to those of the first groove portion 12’ illustrated in figures 1-3, the groove sub-portions 12A’” and 12B” have a geometric configuration and curvature characteristics substantially similar to those of the second groove portion 12” illustrated in figures 1 -3.

[0345] Conversely, the groove sub-portion 12A”, arranged astride between the first lateral annular sub-portion L2’, L3’ and the second lateral annular sub-portion L2”, L3” of the tread band 10, has a geometric configuration and curvature characteristics substantially similar to those of the first groove portion 12’ in a part of the groove sub-portion 12A” proximal to the equatorial plane X-X, and similar to those of the second groove portion 12” in a part of the groove sub-portion 12A” distal with respect to the equatorial plane X-X.

[0346] In the embodiment of figure 5, a variant of the tread band 10 is illustrated in which the transversal grooves 12 formed in the lateral annular portions L2, L3 of the tread band 10 comprise the aforementioned first and second transversal grooves 12A and 12B illustrated above with reference to the preferred embodiment of figure 4.

[0347] In this case, however, the transversal grooves 12A and the transversal grooves 12B are preferably circumferentially consecutive and are arranged alternate with PIR478B

[0348] 37 each other along the circumferential development of the tyre 1 .

[0349] In the embodiment of figure 6, a variant of the tread band 10 is illustrated in which the transversal grooves 12 formed in the lateral annular portions L2, L3 of the tread band 10 comprise a first groove portion 12’ lying in the first lateral annular sub-portion L2’, L3’ comprising a plurality of substantially rectilinear sub-portions or, segments, consecutive and substantially rectilinear, for example the two segments indicated with the references 12’c and 12’d.

[0350] In the embodiment of figure 6, the segment indicated with the reference 12’c is entirely arranged in the first annular sector S, while the segment 12’d is substantially arranged for its almost totality (except for a small portion of substantially triangular shape indicated with k in figure 6), in the first lateral annular sub-portion L2’, L3’ between the axially outer end Se of the first annular sector S and the axially outer end of the first lateral annular sub-portion L2’, L3’.

[0351] Preferably, the consecutive segments 12’c and 12’d of the first groove portion 12’ form therebetween a vertex V1 that is circumferentially oriented in the same direction with respect to the rolling direction F of the tyre 1 .

[0352] Preferably, the consecutive segments 12’c and 12’d of the first groove portion 12’ form therebetween a vertex angle betaccomprised between 130° and 165°, while the axially outermost segment 12’d from the equatorial plane X-X forms with the second groove portion 12” a vertex angle betad comprised between 130° and 170°.

[0353] In this preferred embodiment, the directrix g’ of the first groove portion 12’ comprises in turn two segments g'c and g'd forming with the equatorial plane X- X respective increasing angles alpha’c and alpha’d moving away from the equatorial plane X-X.

[0354] Specifically, the angle alpha’c may be comprised between 15° and 50° and the angle alpha’d may be comprised between 30° and 65°. For the sake of clarity, these angles have been indicated in figure 6 with reference to first groove portions 12’ belonging to different grooves 12.

[0355] In this preferred embodiment, the first transversal rib portion 13’ of the transversal ribs 13 comprises a plurality of substantially rectilinear sub-portions or, segments, consecutive and substantially rectilinear, for example the three segments indicated with the references 13’c and 13’d. PIR478B

[0356] 38

[0357] In this preferred embodiment, the segment indicated with the reference 13’c is entirely arranged in the first annular sector S, while the segment 13’d is substantially arranged in the first lateral annular sub-portion L2’, L3’ between the axially outer end Se of the first annular sector S and the axially outer end of the first lateral annular sub-portion L2’, L3’.

[0358] In this preferred embodiment, the first transversal rib portion 13’ of the transversal ribs 13 formed in the lateral annular portions L2, L3 of the tread band 10 is substantially tapered in a direction from a shoulder portion of the tyre 1 toward the equatorial plane X-X of the tyre 1 .

[0359] In this preferred embodiment, the second transversal rib portion 13” of the transversal ribs 13 is substantially rectilinear.

[0360] Figure 12 illustrates the course of the width of the transversal ribs 13 formed in the tread band 10 as a function of the distance from the equatorial plane X-X within the axial half-development L / 2 of the tread band 10 with reference to the tyre 1 of figure 6 having a size of 120 / 70 R17.

[0361] Similarly to figure 10, mentioned above, also in figure 12, the absolute values in mm of the width of the transversal ribs 13 as a function of the % distance from the equatorial plane X-X of the tyre 1 are indicated in ordinate.

[0362] As can be seen from the graph shown in figure 12, the width of the transversal ribs 13 increases from 3% to 68% passing from a given annular area A to an axially adjacent annular area A of said reference system in the first annular sector S defined in the first lateral annular sub-portion (L2’ in this case) and moving away from the equatorial plane X-X. In addition, in this embodiment, in the remaining part of the first lateral annular sub-portion L2’ axially outside the first annular sector S, the width of the first transversal rib portion 13’ increases with a “step-like” course moving away from the equatorial plane X-X.

[0363] Conversely, the width of the transversal ribs 13 in the second lateral annular subportion L2” of the tread band 10 remains substantially constant also in this case moving away from the equatorial plane X-X of the tyre 1 .

[0364] In the embodiment of figure 7, an additional variant of the tread band 10 is illustrated in which the transversal grooves 12 formed in the lateral annular portions L2, L3 of the tread band 10 comprise a first groove portion 12’ lying in the first lateral annular sub-portion L2’, L3’ comprising a plurality of substantially rectilinear sub-portions or, segments, consecutive and substantially rectilinear, PIR478B

[0365] 39 for example the three segments indicated with the references 12’c, 12’d and 12’e.

[0366] In the embodiment of figure 7, the segments indicated with the references 12’c, 12’d are entirely arranged in the first annular sector S, while the segment 12’e is substantially arranged for its almost totality (except for a small portion of substantially triangular shape indicated with k in figure 7), in the first lateral annular sub-portion L2’ , L3’ between the axially outer end Se of the first annular sector S and the axially outer end of the first lateral annular sub-portion L2’ , L3’.

[0367] Preferably, the consecutive segments 12’c, 12’d and 12’e of the first groove portion 12’ form therebetween vertices V1 and V2 that are circumferentially oriented in the same direction with respect to the rolling direction F of the tyre 1 .

[0368] Preferably, the consecutive segments 12’c, 12’d and 12’e of the first groove portion 12’ form therebetween a vertex angle betaccomprised between 130° and 165° and betad comprised between 130° and 170°, while the axially outermost segment 12’e from the equatorial plane X-X forms with the second groove portion 12” a vertex angle betaecomprised between 130° and 178°.

[0369] In this preferred embodiment, the directrix g’ of the first groove portion 12’ comprises in turn three segments g'c, g 'd and g'e forming with the equatorial plane X-X respective increasing angles alpha’c, alpha’d and alpha’e moving away from the equatorial plane X-X.

[0370] Specifically, the angle alpha’c may be comprised between 15° and 35°, the angle alpha’d may be comprised between 25° and 50°, and the angle alpha’e may be comprised between 35° and 80°. For the sake of clarity, these angles have been indicated in figure 7 with reference to first groove portions 12’ belonging to different grooves 12.

[0371] In this preferred embodiment, the first transversal rib portion 13’ of the transversal ribs 13 comprises a plurality of substantially rectilinear sub-portions or, segments, consecutive and substantially rectilinear, for example the three segments indicated with the references 13’c, 13’d and 13’e.

[0372] In this preferred embodiment, the three segments indicated with the references 13’c and 13’d are entirely arranged in the first annular sector S, while the segment 13’e is substantially arranged in the first lateral annular sub-portion L2’, L3’ between the axially outer end Se of the first annular sector S and the axially outer end of the first lateral annular sub-portion L2’, L3’. PIR478B

[0373] 40

[0374] In this preferred embodiment, the first transversal rib portion 13’ of the transversal ribs 13 formed in the lateral annular portions L2, L3 of the tread band 10 is substantially tapered in a direction from a shoulder portion of the tyre 1 toward the equatorial plane X-X of the tyre 1 .

[0375] In this preferred embodiment, the second transversal rib portion 13” of the transversal ribs 13 is also substantially rectilinear.

[0376] In the preferred embodiments illustrated in figures 8 and 9, variants of the embodiment of the tyre 1 are illustrated in which the tread band 10 comprises at least one longitudinal groove 20 formed in the central annular portion L1 of the tread band 10.

[0377] In the preferred embodiment illustrated in figure 8, the tyre 1 has a configuration of the tread band 10 substantially similar to that illustrated above with reference to the preferred embodiment illustrated in figures 1 -3.

[0378] In the preferred embodiment of figure 8, the tread band 10 of the tyre 1 comprises at least two longitudinal grooves 20 formed in the central annular portion L1 and symmetrically arranged on opposite sides with respect to the equatorial plane X- X of the tyre 1 .

[0379] Similarly to the previous embodiments, the central annular portion L1 of the tread band 10 is axially delimited by the axially inner ends 12’a of the first groove portion 12’ of the transversal grooves 12 formed in the first lateral annular sub-portion L2’, L3’ of the tread band 10 on opposite sides of the equatorial plane X-X.

[0380] In a preferred alternative embodiment, not illustrated, the tread band 10 can comprise four longitudinal grooves 20, formed in the central annular portion L1 and symmetrically arranged on opposite sides with respect to the equatorial plane X-X of the tyre 1 .

[0381] Preferably, the longitudinal grooves 20 have an axial extension comprised between 1 % and 8%, of an axial half-development L / 2 of the tread band 10.

[0382] The two longitudinal grooves 20, or the two axially innermost longitudinal grooves 20 of the four longitudinal grooves 20, define a circumferential rib 21 arranged astride of the equatorial plane X-X of the tyre 1 .

[0383] Preferably, the circumferential rib 21 arranged astride of the equatorial plane X- X of the tyre 1 has an axial extension comprised between 10% and 16% of the PIR478B

[0384] 41 axial half-development L / 2 of the tread band 10.

[0385] In an additional alternative preferred embodiment, not illustrated, the tread band 10 can comprise a longitudinal groove 20 formed astride of the equatorial plane X-X of the tyre 1 .

[0386] In an additional alternative preferred embodiment, not illustrated, the tread band 10 can comprise a central longitudinal groove 20 formed astride of the equatorial plane X-X of the tyre 1 and two longitudinal grooves 20 formed in the central annular portion L1 and symmetrically arranged on opposite sides with respect to said central longitudinal groove 20.

[0387] Preferably, the axially inner end 12’a of the first groove portion 12’ of the transversal grooves 12 formed in the first lateral annular sub-portion L2’, L3’ of the tread band 10 is arranged at a predetermined distance “d” from an axially outer longitudinal groove 20 of the longitudinal grooves 20 formed in the central annular portion L1 of the tread band 10.

[0388] In this way, a circumferential solid portion 16 of tread band is defined in the tread band 10 which is axially arranged between the axially outermost longitudinal groove 20 of the longitudinal grooves 20 and the axially inner end 12'a of the first groove portion 12’ of the transversal grooves 12 formed in the first lateral annular sub-portion L2’, L3’ of the tread band 10.

[0389] Preferably, the circumferential solid portion 16 of tread band is integral with the transversal ribs 13 formed in the lateral annular portions L2, L3 of the tread band 10, specifically with the first transversal rib portion 13’ in figure 8 and 13’c in figure 9, positioned in the first lateral annular sub-portion L2’, L3’ of the tread band 10.

[0390] Preferably, the distance “d” between said axially inner end 12’a of the first groove portion 12’ of the transversal grooves 12 formed in the first lateral annular subportion L2’, L3’ of the tread band 10 and the axially outermost longitudinal groove 20 of the longitudinal grooves 20 formed in the central annular portion L1 of the tread band 10, is comprised between 1 % and 9%, of the axial half-development L / 2 of the tread band 10.

[0391] Correspondingly, therefore, the circumferential solid portion 16 of tread band 10 axially arranged between the axially outermost longitudinal groove 20 and the axially inner end 12’a of the first groove portion 12’ of the transversal grooves 12 formed in the first lateral annular sub-portion L2’, L3’ of the tread band 10 has an axial extension, identifiable with the aforementioned distance “d”, which is entirely PIR478B

[0392] 42 similar.

[0393] In this preferred embodiment and due to the presence of the aforementioned longitudinal grooves 20, the axial extensions of the various annular portions of the tread band 10 with respect to the axial development L of the tread band 10 are as follows:

[0394] - central annular portion L1 : 1 %-22%, more preferably 14%-18%,

[0395] - lateral annular portions L2, L3: 38%-49.5%, more preferably 38%-46%,

[0396] - first lateral annular sub-portions L2’, L3’: 20-32%, more preferably 22%-30%,

[0397] - second lateral annular sub-portions L2”, L3”: 6%-29.5%, more preferably 8-24%.

[0398] Figure 1 1 illustrates the course of the width of the transversal ribs 13 formed in the tread band 10 as a function of the distance from the equatorial plane X-X within the axial half-development L / 2 of the tread band 10 with reference to the tyre 1 of figure 8 having a size of 120 / 70 R17.

[0399] Similarly to figure 10, mentioned above, also in figure 11 , the absolute values in mm of the width of the transversal ribs 13 as a function of the % distance from the equatorial plane X-X of the tyre 1 are indicated in ordinate.

[0400] As can be seen from the graph reported in figure 11 , the width of the transversal ribs 13 gradually increases in the first annular sector S defined in the first lateral annular sub-portion (L2’ in this case) and moving away from the equatorial plane X-X.

[0401] In this case, the beginning of the graph is shifted towards the shoulder area of the tyre 1 due to the greater axial extension of the central annular portion L1 arranged astride of the equatorial plane X-X of the tyre 1 which implies a displacement of the transversal ribs 13 towards the shoulder area of the tyre 1 .

[0402] In particular, in this specific example, in the first annular sector S the width of the first transversal rib portion 13’ increases from 3% to 35% passing from a given annular area A to an axially adjacent annular area A of said reference system in the first annular sector S defined in the first lateral annular sub-portion (L2’ in this case) and moving away from the equatorial plane X-X. Conversely, the width of the transversal ribs 13 in the second lateral annular sub-portion L2” of the tread band 10 also remains substantially constant in this case moving away from the equatorial plane X-X of the tyre 1 . PIR478B

[0403] 43

[0404] In the preferred embodiment of figure 9, a variant of the tyre 1 of Fig. 6 is illustrated in which the transversal grooves 12 formed in the lateral annular portions L2, L3 of the tread band 10 comprise a first groove portion 12’ lying in the first lateral annular sub-portion L2’, L3’ comprising a plurality of substantially rectilinear sub-portions or, segments, consecutive and substantially rectilinear, for example the two segments indicated with the references 12’c and 12’d.

[0405] In the embodiment of figure 9, the segment indicated with the reference 12’c is arranged in the first annular sector S, while the segment 12’d is substantially arranged in the first lateral annular sub-portion L2’, L3’ between the axially outer end Se of the first annular sector S and the axially outer end of the first lateral annular sub-portion L2’, L3’.

[0406] Preferably, the consecutive segments 12’c and 12’d of the first groove portion 12’ form therebetween a vertex V1 that is circumferentially oriented in the same direction with respect to the rolling direction F of the tyre 1 .

[0407] Preferably, the consecutive segments 12’c and 12’d of the first groove portion 12’ form therebetween a vertex angle betac, while the axially outermost segment 12’d from the equatorial plane X-X forms with the second groove portion 12” a vertex angle betad, the angles betacand betad having the same value as the one indicated above with reference to figure 6.

[0408] In this preferred embodiment, the directrix g’ of the first groove portion 12’ comprises in turn two segments g'c and g'd forming with the equatorial plane X- X respective increasing angles alpha’c and alpha’d moving away from the equatorial plane X-X, the angles alpha’c and alpha’d having the same value as the one indicated above with reference to figure 6.

[0409] For greater clarity, all the aforementioned angles have been indicated in figure 9 with reference to first groove portions 12’ belonging to different grooves 12.

[0410] In this preferred embodiment, the first transversal rib portion 13’ of the transversal ribs 13 comprises a plurality of substantially rectilinear sub-portions or, segments, consecutive and substantially rectilinear, for example the two segments indicated with the references 13’c and 13’d.

[0411] In this preferred embodiment, the segment indicated with the reference 13’c is arranged in the first annular sector S, while the segment 13’d is substantially arranged in the first lateral annular sub-portion L2’, L3’ between the axially outer end Se of the first annular sector S and the axially outer end of the first lateral PIR478B

[0412] 44 annular sub-portion L2’, L3’.

[0413] Also in this preferred embodiment, the first transversal rib portion 13’ of the transversal ribs 13 formed in the lateral annular portions L2, L3 of the tread band 10 is substantially tapered in a direction from a shoulder portion of the tyre 1 toward the equatorial plane X-X of the tyre 1 .

[0414] In this preferred embodiment, the second transversal rib portion 13” of the transversal ribs 13 is also substantially rectilinear.

[0415] Figure 13 illustrates the course of the width of the transversal ribs 13 formed in the tread band 10 as a function of the distance from the equatorial plane X-X within the axial half-development L / 2 of the tread band 10 with reference to the tyre 1 of figure 9 having a size of 120 / 70 R17.

[0416] Similarly to figure 10, mentioned above, also in figure 13, the absolute values in mm of the width of the transversal ribs 13 as a function of the % distance from the equatorial plane X-X of the tyre 1 are indicated in ordinate.

[0417] As can be seen from the graph reported in figure 13, the width of the transversal ribs 13 increases from 3% to 68% passing from a given annular area A to an axially adjacent annular area A of said reference system in the first annular sector S defined in the first lateral annular sub-portion (L2’ in this case) and moving away from the equatorial plane X-X.

[0418] Furthermore, in this embodiment, in the first annular sector S and in the remaining axially outer part of the first lateral annular sub-portion L2’ with respect to the first annular sector S, the width of the first transversal rib portion 13’ increases with a “step-like” course moving away from the equatorial plane X-X.

[0419] Similarly to the graph of figure 11 , also in this case the beginning of the graph is shifted towards the shoulder area of the tyre 1 due to the greater axial extension of the central annular portion L1 arranged astride of the equatorial plane X-X of the tyre 1 which implies a displacement of the transversal ribs 13 towards the shoulder area of the tyre 1 .

[0420] Conversely, the width of the transversal ribs 13 in the second lateral annular subportion L2” of the tread band 10 remains substantially constant also in this case moving away from the equatorial plane X-X of the tyre 1 .

[0421] The invention will now be illustrated by means of some Examples to be PIR478B

[0422] 45 considered for illustrative and not limiting purposes thereof.

[0423] Outdoor tests on tyres

[0424] The Applicant, in view of improving the constancy of driving and grip performance on wet or humid ground, in particular when the camber angle changes between travel along a straight course and cornering, took as base of the comparative riding test the tyre for a front wheel by Pirelli model Diablo™ Rain 120 / 70 R17, which was and still is a reference tyre that is highly appreciated by sports users.

[0425] Different test sessions were carried out in a private racetrack, carrying out a series of manoeuvres to test grip and manoeuvrability on a wet surface. The rider’s evaluation is an average of the evaluations attributed in the various manoeuvres.

[0426] In the test on the wet surface the conditions were: tyre inflation pressure 1 .9 bar; temperature of the asphalt of the track 23°C; air temperature 21 °C.

[0427] The tests were carried out with motorcycles of the “Super sport” segment, model YAMAHA R1 M and BMW S 1000 RR STOCK.

[0428] The following Table 1 summarizes the marks given by the test driver in the tests on wet surface, for the various types of performance required of the tested tyre (average of the evaluations of two test drivers on the motorcycles indicated above).

[0429] In Table 1 the evaluation of performance for the comparative tyre has been indicated with the symbol “=”, whereas - for the tyre according to the invention - an improved performance with respect to the comparative tyre has been indicated by means of the symbol ”+” a greater number of said symbol denoting a greater improved performance.

[0430] Table 1 PIR478B

[0431] 46

[0432] The results given in Table 1 demonstrate that the tyre according to the invention has shown improved behaviour with respect to the already excellent comparative tyre on a wet ground both in terms of manoeuvrability and grip, in particular when the camber angle varied between a straight course travel and cornering. From the tests carried out in particular two groups of improved performance became evident.

[0433] A first group, characterized by the driving quality (in the table indicated in the section “driving fundamentals”) and by the feeling of safety, i.e. by characteristics that allow to ride by selecting different trajectories safely, and thereby allowing to manoeuvre in an optimal manner in race conditions.

[0434] Without wishing to be bound by any interpretative theory, the Applicant deems that this improved performance may be attributed to the “homogeneity” of the tread pattern in terms of “continuity” in the presence of grooves and ribs under the ground contacting area of the tyre both when travelling along a straight course, and when increasing the camber angle (i.e. entering or exiting a bend).

[0435] A second group, correlated to peak performance in the various camber angles tackled (in the table indicated in the “drainage” and “grip” sections). PIR478B

[0436] 47

[0437] Without wishing to be bound by any interpretative theory also in this case, the Applicant deems that this improved performance may be attributed to the interaction between the geometric characteristics of the tread pattern, such as for example the inclination of the grooves and of the transversal ribs and the widths of such elements, and the “homogeneity” of the tread pattern in the terms indicated above of “continuity” in the presence of grooves and ribs under the ground contacting area of the tyre both when travelling along a straight course, and when increasing the camber angle (i.e. entering or exiting a bend).

[0438] During the tests carried out it was also found that significant reductions in the lap times on the racetracks were achieved with the tyres according to the invention.

[0439] Various modifications can be made to the embodiments described in detail, still remaining within the scope of protection of the invention, defined by the following claims.

Claims

PIR478B48CLAIMS1. Motorcycle tyre (1 ), comprising an equatorial plane (X-X) free from transversal grooves and a tread band (10) extending according to an axial development (L), wherein the tread band (10) comprises, in a plan development thereof:- two lateral annular portions (L2, L3) arranged on opposite sides with respect to said equatorial plane (X-X) and each comprising a first lateral annular sub-portion (L2’, L3’), proximal with respect to the equatorial plane (X-X), and a second lateral annular sub-portion (L2”, L3”), distal with respect to the equatorial plane (X-X),- a plurality of transversal grooves (12) formed in the lateral annular portions (L2, L3) of the tread band (10) having an axial extension equal to at least 30%, preferably an axial extension comprised between 39% and 49%, more preferably an axial extension comprised between 44% and 49%, of the axial halfdevelopment (L / 2) of the tread band (10); wherein said first lateral annular sub-portion (L2’, L3’) axially extends along 10%- 32%, preferably along 20%-32% of the axial development (L) of the tread band (10), and comprises a first annular sector (S), proximal with respect to the equatorial plane (X-X), said first annular sector (S) axially extending along 7%- 32%, preferably along 10%-30% of the axial development (L) of the tread band (10); wherein said transversal grooves (12) comprise a first groove portion (12’) lying in said first lateral annular sub-portion (L2’, L3’) and a second groove portion (12”) lying in said second lateral annular sub-portion (L2”, L3”); wherein the first groove portion (12’) has a first directrix (g’) forming with the equatorial plane (X-X) an angle (alpha) having a minimum value (alpha’a) comprised between 15° and 50° at an end (12’a) of the first groove portion (12’) proximal to the equatorial plane (X-X) and a maximum value (alpha’b) comprised between 50° and 80° at an end (12’b) of the first groove portion (12’) distal with respect to the equatorial plane (X-X); wherein said transversal grooves (12) are arranged according to a circumferential succession configured so as to form, between the transversal grooves (12), a circumferential succession of transversal ribs (13) extending up to the axial ends of the tread band (10);PIR478B49 wherein said transversal ribs (13) comprise a first transversal rib portion (13’) lying in said first lateral annular sub-portion (L2’, L3’) and a second transversal rib portion (13”) lying in said second lateral annular sub-portion (L2”, L3”); wherein in said first lateral annular sub-portion (L2’, L3’) a reference system is defined comprising a plurality of axially adjacent annular areas (A) each having an axial extension equal to 3% of the axial development (L) of the tread band (10); wherein, in the first annular sector (S) of the first lateral annular sub-portion (L2’, L3’), said first transversal rib portion (13’) has an increasing width moving away from the equatorial plane (X-X) between an axially inner end (Si) of the first annular sector (S) proximal to the equatorial plane (X-X) and an axially outer end (Se) of the first annular sector (S) distal with respect to the equatorial plane (X- X); wherein in said first annular sector (S) defined in the first lateral annular subportion (L2’, L3’) and moving away from the equatorial plane (X-X), the width of the first transversal rib portion (13’) increases passing from a given annular area (A) to an axially adjacent annular area (A) of said reference system; wherein the second groove portion (12”) has a second directrix (g”) forming with the equatorial plane (X-X) an angle comprised between 50° and 80° at an end of the second groove portion (12”) proximal to the equatorial plane (X-X) and an angle comprised between 80° and 90° at an end of the second groove portion (12”) distal with respect to the equatorial plane; and wherein said second transversal rib portion (13”) has a substantially constant width comprised between 5% and 60%, preferably between 6% and 12%, of an axial half-development (L / 2) of the tread band (10).

2. Motorcycle tyre (1 ) according to claim 1 , wherein said tread band (10) comprises, in a plan development thereof, a central annular portion (L1 ) arranged astride of the equatorial plane (X-X) of the tyre (1 ).

3. Motorcycle tyre (1 ) according to claim 2, wherein said first annular sector (S) of the first lateral annular sub-portion (L2’, L3’) is axially arranged outside of and adjacent to the central annular portion (L1 ).

4. Motorcycle tyre (1 ) according to claim 2, wherein the central annular portion (L1 ) of the tread band (10) axially extends along 1 %-22%, preferablyPIR478B50 along 1 %-4.5% or along 12-22%, of the axial development (L) of the tread band (10).

5. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein each of said lateral annular portions (L2, L3) of the tread band (10) axially extends along 38%-49.5%, preferably along 47.75%-49.5% or along 38%-46%, of the axial development (L) of the tread band (10).

6. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein said second lateral annular sub-portion (L2”, L3”) of the lateral annular portions (L2, L3) axially extends along 10%-32%, preferably along 20%-28%, of the axial development (L) of the tread band (10).

7. Motorcycle tyre (1 ) according to any one of claims 2-6, wherein the tread band (10) comprises in said central annular portion (L1 ) a circumferential solid portion (14) axially arranged between axially inner ends (12’a) of first groove portions (12’) proximal to the equatorial plane (X-X) arranged on opposite sides with respect to the equatorial plane (X-X).

8. Motorcycle tyre (1 ) according to claim 7, wherein said circumferential solid portion (14) of tread band (10) is integral with the first transversal rib portion (13’) of said transversal ribs (13) and is preferably arranged astride of the equatorial plane (X-X) of the tyre (1 ).

9. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein said first transversal rib portion (13’) has a minimum width, measured at an axially inner end (13’a) thereof, comprised between 3% and 25%, more preferably between 4% and 6%, of the axial half-development (L / 2) of the tread band (10), and a maximum width, measured at the axially outer end thereof (13’b), comprised between 5% and 55 %, more preferably between 6.5% and 40%, of the axial half-development (L / 2) of the tread band (10).

10. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein a width of said first transversal rib portion (13’), measured at an axially outer end (Se) of the first annular sector (S), is comprised between 4% and 35%, more preferably between 4% and 25%, of the axial half-development (L / 2) of the tread band (10).11 . Motorcycle tyre (1 ) according to any one of the preceding claims, wherein a ratio between a width of said first transversal rib portion (13’), measured at an axially outer end (Se) of the first annular sector (S), and a minimum width,PIR478B51 measured at an axially inner end (13’a) of said first transversal rib portion (13’), is comprised between 1 .3 and 3.7.

12. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the first directrix (g’) of the first groove portion (12’) of the transversal grooves (12) forms with the equatorial plane (X-X) an increasing, preferably progressively increasing, angle (alpha) moving away from the equatorial plane (X-X) from said minimum value (alpha’a) to said maximum value (alpha’b).

13. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein, in said first annular sector (S) defined in the first lateral annular sub-portion (L2’, L3’) and moving away from the equatorial plane (X-X), the width of the first transversal rib portion increases, preferably progressively, not more than 70%, preferably the width of the first transversal rib portion increases from 1 % to 40%, even more preferably from 3% to 40%, even more preferably from 3% to 35%, passing from a given annular area (A) to an axially adjacent annular area (A) of said reference system.

14. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the first groove portion (12’) of the transversal grooves (12) has a substantially curvilinear course forming a concavity circumferentially oriented in the same direction or in an opposite direction with respect to the rolling direction (F) of the tyre (1 ).

15. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein said first transversal groove portion (12’) is at least partially tapered in a direction from a shoulder portion of the tyre (1 ) towards the equatorial plane (X-X) of the tyre (1 ).

16. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein said first transversal groove portion (12’) has a minimum width, measured at an axially inner end thereof (12’a), comprised between 2.5% and 6.5%, preferably between 3% and 5%, of an axial half-development (L / 2) of the tread band (10) and a maximum width, measured at an axially outer end thereof (12’b), comprised between 3.5% and 9%, preferably between 5% and 8%, of an axial halfdevelopment (L / 2) of the tread band (10).

17. Motorcycle tyre (1 ) according to claim 16, wherein in said first lateral annular sub-portion (L2’, L3’) a ratio between a maximum width of said first transversal groove portion (12’) measured at an axially outer end (12’b) of saidPIR478B52 first transversal groove portion (12’) and a minimum width measured at an axially inner end (12’a) of said first transversal groove portion (12’) is comprised between 1.2 and 2.

18. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein said second transversal groove portion (12”) has a width comprised between 2% and 10%, preferably between 3.5% and 6%, of an axial half-development (L / 2) of the tread band (10).

19. Motorcycle tyre (1 ) according to any one of claims 1 -12, wherein said first transversal groove portion (12’) comprises at least two substantially rectilinear sub-portions (12’c, 12’d, 12’e) forming therebetween a vertex (V1 , V2) that is circumferentially oriented in the same direction or in an opposite direction with respect to the rolling direction (F) of the tyre (1 ).

20. Motorcycle tyre (1 ) according to claim 19, wherein said sub-portions (12’c, 12’d, 12’e) of said first transversal groove portion (12’) form therebetween a vertex angle (beta) comprised between 135° and 179°.21 . Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the tread band (10) comprises a plurality of transversal grooves (12A, 12B), formed in the lateral annular portions (L2, L3) of the tread band (10), which comprise a plurality of groove sub-portions (12A’, 12A” and 12A’”; 12B’ and 12B”) separated by a solid part (15A’, 15A”; 15B) of tread band, and wherein each solid part (15A’, 15A”; 15B) has a length, measured along a directrix (gA, gB) of said transversal grooves (12A, 12B), not greater than 25%, preferably comprised between 2.5% and 25%, of the total length of the transversal grooves (12A, 12B) measured along said directrix (gA, gB).

22. Motorcycle tyre (1 ) according to claim 21 , wherein said groove subportions (12A’, 12A” and 12A’”; 12B’ and 12B”) of the transversal grooves (12A, 12B) formed in the lateral annular portions (L2, L3) of the tread band (10) have a length, measured along the directrix (gA, gB) of said transversal grooves (12A, 12B), comprised between 20% and 75% of the total length of the transversal grooves (12A, 12B).

23. Motorcycle tyre (1 ) according to any one of claims 2-22, wherein the tread band (10) comprises at least one longitudinal groove (20) formed in the central annular portion (L1 ) of the tread band (10) or at least two longitudinal grooves (20) formed in the central annular portion (L1 ) and arranged, preferablyPIR478B53 symmetrically, on opposite sides with respect to the equatorial plane (X-X) of the tyre (1 ).

24. Motorcycle tyre (1 ) according to claim 23, wherein an axially inner end (12’a) of said first transversal groove portion (12’) is arranged at a predetermined distance (d) from said at least one longitudinal groove (20), or from an axially outermost longitudinal groove (20) of said at least two longitudinal grooves (20), so as to form a circumferential solid portion (16) of tread band (10) axially arranged between said axially inner end (12’a) of said first transversal groove portion (12’) and said at least one longitudinal groove (20), or said axially outermost longitudinal groove (20) of said at least two longitudinal grooves (20).

25. Motorcycle tyre (1 ) according to claim 24, wherein said circumferential solid portion (16) of tread band (10) arranged between said axially inner end (12’a) of said first transversal groove portion (12’) and said at least one longitudinal groove (20), or said axially outermost longitudinal groove (20) of said at least two longitudinal grooves (20), is integral with said first transversal rib portion (13’).

26. Motorcycle tyre (1 ) according to any one of claims 23-25, wherein said at least one longitudinal groove (20) is formed at, preferably astride of, the equatorial plane (X-X) of the tyre (1 ).

27. Motorcycle tyre (1 ) according to claim 23, wherein said at least one or said at least two longitudinal grooves (20) have an axial extension comprised between 1 % and 8% of the axial half-development (L / 2) of the tread band (10).

28. Motorcycle tyre (1 ) according to claim 23, wherein said at least two longitudinal grooves (20) formed in the central annular portion (L1 ) and arranged on opposite sides with respect to the equatorial plane (X-X) of the tyre (1 ) define a circumferential rib (21 ) arranged astride of the equatorial plane (X-X) of the tyre (1 ).

29. Motorcycle tyre (1 ) according to claim 28, wherein said circumferential rib (21 ) arranged astride of the equatorial plane (X-X) of the tyre (1 ) has an axial extension comprised between 10% and 16% of the axial half-development (L / 2) of the tread band (10).

30. Motorcycle tyre (1 ) according to any one of claims 24-29, wherein said distance (d) between said axially inner end (12’a) of said first transversal groove portion (12’) and said at least one longitudinal groove (20), or an axially outermostPIR478B54 longitudinal groove (20) of said at least two longitudinal grooves (20), is comprised between 1 % and 9% of an axial half-development (L / 2) of the tread band (10).31 . Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the tyre (1 ) is a tyre for a front motorcycle wheel and has a transversal curvature ratio greater than or equal to 0.20, preferably greater than or equal to 0.25, more preferably greater than or equal to 0.30 and lower than or equal to 0.50, preferably lower than or equal to 0.45.

32. Motorcycle tyre (1 ) according to any one of claims 1 -30, wherein the tyre (1 ) is a tyre for a rear motorcycle wheel and has a transversal curvature ratio greater than or equal to 0.20, preferably greater than or equal to 0.25, more preferably greater than or equal to 0.29 and lower than or equal to 0.40, preferably lower than or equal to 0.35.

33. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the tyre (1 ) has a nominal fitting diameter comprised between 10” and 18”.

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