Motorcycle tyre

Abstract

A tyre (1) for motorcycle wheels is described comprising an equatorial plane (XX) and a tread band (8) extending according to an axial development (L), wherein the tread band (8) comprises, in a plan development thereof, a central annular portion (L1) arranged astride of the equatorial plane (X-X) of the tyre (1) and 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 the tyre (1). The tread band (8) also comprises at least one longitudinal groove (20) formed in the central annular portion (L1) and a plurality of transversal grooves (33) substantially parallel to one another, formed in the lateral annular portions (L2, L3) of the tread band (8). The transversal grooves (33) obliquely extend with respect to the equatorial plane (X-X) of the tyre (1) according to an angle of inclination comprised between 40° and 75° with respect to the equatorial plane (X-X) and form therebetween a circumferential succession of transversal ribs (34) which extend up to the axial ends of the tread band. An axially inner end (33a) of the transversal grooves (33) is arranged at a predetermined distance (d) from the longitudinal groove (20) so as to form a circumferential solid portion (35) of tread band (8), axially arranged between the axially inner end (33a) of the transversal grooves (33) and the longitudinal groove (20), and integrally formed with the transversal ribs (34).

Description

[0001] Motorcycle tyre

[0002] Field of the invention

[0003] The present invention relates 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 term of “motorcycle tyre”.

[0005] In particular, the present invention relates 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 (which may achieved, for example, on track), and in the case of Supersport motorcycles approved for road use, for road uses of the vehicle throughout the year in wet or humid surface conditions and / or in cold weather or in non-optimal road surface, all in combination with a good wear resistance.

[0010] In order to provide a motorcycle tyre in which it is possible to achieve both wear resistance and driving stability on wet ground, the aforementioned patent application EP 1 473 176 A1 discloses 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 wet driving stability.

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

[0012] 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 wear resistance is high.

[0013] Patent application EP 1 473 176 A1 further discloses a first comparative tyre, illustrated in Fig. 6 of this document, provided with a tread pattern comprising a plurality of inclined grooves forming an angle of about 28° with respect to the circumferential direction of the tyre close to its equatorial plane.

[0014] Such an angle gradually increases in an axially outer end portion of the grooves positioned in the shoulder area of the tyre until it forms an angle close to 90° with the equatorial plane of the tyre.

[0015] The tread pattern also comprises a plurality of inclined grooves having an axially limited length, called “sub-grooves”, formed between the inclined grooves in the shoulder area of the tyre.

[0016] Patent application EP 1 473 176 A1 also discloses a second comparative tyre, illustrated in Fig. 7 of this document, provided with a tread pattern having three circumferential grooves arranged on opposite sides of the equatorial plane of the tyre and defining therebetween five circumferential ribs in a central annular portion of the tread band having a significant axial extension.

[0017] The tread pattern of this comparative tyre also comprises a plurality of inclined grooves 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.

[0018] In relation to the first tyre disclosed by patent application EP 1 473 176 A1 , the Applicant has observed that such a tyre can have a lower overall draining capability of the tyre in driving conditions on a wet or humid surface, whereas the aforementioned stiffness of the tread band in the shoulder areas of the tyre can result in such driving conditions into less grip at high camber, i.e. in so-called “full bend” conditions of the motorcycle. In relation to the first comparative tyre described in figure 6 of patent application EP 1 473 176 A1 , on the other hand, the Applicant has observed that such a tyre can have both irregular wear close to the radially inner ends of the aforementioned sub-grooves formed in the shoulder areas of the tyre, and a worsening of the driving safety and comfort characteristics as the camber angle increases in so-called “full bend” driving conditions .

[0019] In relation to the second comparative tyre disclosed in figure 7 of patent application EP 1 473 176 A1 , finally, the Applicant has observed that when shifting from travel along a straight course (in which the tyre is substantially perpendicular to the ground) to a slight camber 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 traction performance in wet driving conditions.

[0020] In particular, the Applicant has observed that with a tyre of this type when shifting from travel along a straight course to a slight camber there can be a deterioration of the grip performance of the motorcycle that can impose to the pilot applying less power than what it would be desirable in sports driving or in races.

[0021] 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.

[0022] This motorcycle tyre comprises a tread pattern consisting of a central portion of the tread having a width equal to 60% of the developed width of the tread and lateral portions of the tread pattern arranged outside of the central portion of the tread in the width direction of the tyre.

[0023] 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.

[0024] 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 a width of the lateral portion of the tread.

[0025] In relation to the tyre disclosed 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 camber of the motorcycle, the configuration of the tread pattern with inclined grooves connected to the circumferential grooves 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 driving conditions.

[0026] In particular, the Applicant has observed that with a tyre of this type when shifting from travel along a straight course to a slight camber there can be a deterioration of the grip performance of the motorcycle that can impose to the pilot applying less power than what it would be desirable in sports driving or in races.

[0027] 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 with a suitable configuration of the tread pattern it is possible to achieve an important improvement in terms of consistency of such performances as the camber angle of the tyre changes.

[0028] In particular, the Applicant has surprisingly found that it is possible to achieve the aforementioned objective thanks to a combination of the following provisions:

[0029] - suitably limiting the transversal width of a central annular portion of the tread band provided with at least one longitudinal groove,

[0030] - forming, in lateral annular portions of the tread band, transversal grooves obliquely extending with respect to the equatorial plane of the tyre according to a predetermined and substantially constant angle of inclination so as to define therebetween a plurality of oblique ribs extending up to the axial ends of the tread band and having a substantially constant width; and

[0031] - arranging an axially inner end of the transversal grooves at a predetermined distance from the at least one longitudinal groove formed in the central annular portion of the tread band to form a circumferential solid portion of tread band integrally connected with the aforementioned oblique ribs.

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

[0033] More particularly, such a tyre comprises an equatorial plane and a tread band extending according to an axial development, wherein the tread band comprises, in a plan development thereof:

[0034] - a central annular portion arranged astride of the equatorial plane of the tyre;

[0035] - two lateral annular portions arranged on opposite sides of the central annular portion with respect to the equatorial plane of the tyre.

[0036] Preferably, the tread band comprises:

[0037] - at least one longitudinal groove formed in the central annular portion of the tread band, or

[0038] - at least two longitudinal grooves formed in the central annular portion and arranged on opposite sides with respect to the equatorial plane of the tyre.

[0039] Preferably, the tread band comprises a plurality of transversal grooves formed in the lateral annular portions of the tread band and obliquely extending with respect to the equatorial plane of the tyre according to an angle of inclination comprised between 40° and 75° with respect to said equatorial plane.

[0040] Preferably, the central annular portion of the tread band transversally extends along 5-30% of the axial development of the tread band.

[0041] Preferably, said transversal grooves have an axial extension equal to at least 30% of the axial development of the tread band.

[0042] Preferably, said transversal grooves are substantially parallel to one another substantially for their entire axial extension and 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.

[0043] Preferably, said transversal ribs have a substantially constant width and obliquely extend with respect to the equatorial plane of the tyre according to said angle of inclination comprised between 40° and 75° with respect to said equatorial plane.

[0044] Preferably, an axially inner end of the transversal grooves formed in the lateral annular portions of the tread band is arranged at a predetermined distance from: 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, so as to form a circumferential solid portion of tread band axially arranged between said axially inner end of the transversal grooves and said at least one longitudinal groove, or said axially outermost longitudinal groove of said at least two longitudinal grooves.

[0045] Preferably, said circumferential solid portion of tread band is integral with said transversal ribs formed in the lateral annular portions of the tread band.

[0046] Without wishing to be bound by any interpretative theory, the Applicant deems that by suitably limiting the transversal width of the central annular portion of the tread band provided with one or more longitudinal grooves, the transversal grooves formed in the lateral annular portions of the tread band always have at least a portion thereof within the ground contacting area of the tyre in all driving conditions of the motorcycle, i.e., in straight course travel conditions (with camber angle substantially equal to 0°), slightly cambering (for example with camber angles of less than 30°) and during a more pronounced camber (for example with camber angles greater than 30°).

[0047] More particularly, this last characteristic advantageously allows to have a homogeneous handling response to changes in the camber angle and an improvement in thrust during acceleration of the tyre thanks to a “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 in straight course travel conditions, and while increasing the camber angle (i.e. entering or exiting a bend).

[0048] The Applicant deems in particular that the aforementioned configuration of the tread pattern is capable of ensuring, in all the driving conditions of the motorcycle (travel along a straight course, slight cambering and more pronounced camber), both an adequate water drainage, and an effective contact between the edges of the aforementioned transversal grooves and the road surface that results in a continuity of interaction between the tyre and the road surface itself.

[0049] 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.

[0050] The Applicant has in particular experimentally found in tests carried out on track that will be discussed hereinafter, that the tyre of the invention, in particular a rear motorcycle tyre, achieves not only an improved performance in terms of progressivity and driving easiness, but also an improved handling and traction performance in all wet driving conditions and in particular at high camber angles. All this results in an increased safety feeling of the driver that in a race allows the driver to follow more trajectories and therefore to improve the so-called “up to the limit” performance.

[0051] The Applicant has in fact experimentally observed in track tests that these improvements in terms of progressivity and driving easiness, handling and traction of the tyre, in particular thrust during acceleration, allowed to achieve significant improvements in lap time in the case of sports use, which results in significantly improved safety margins in the case of road use.

[0052] All this, improving water drainage performance under the ground contacting area of the tyre without jeopardizing the wear resistance of the tyre itself.

[0053] Achieving an improved performance in terms of progressivity and driving easiness, handling and traction at all camber angles on wet ground was surprising, since, with respect to existing tread patterns, a tread pattern of the aforementioned type seemed not to be very suitable for providing an improved performance in these driving conditions either in terms of drainage and in terms of contact feeling and wear, in particular in the shoulder areas of the tyre.

[0054] For the purposes of the present invention, the following definitions apply.

[0055] 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.

[0056] 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. 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.

[0057] The term “average inclination” or “average angle” of a groove is used to indicate the arithmetic average of the inclinations / angles 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.

[0058] The term “equatorial plane” of the tyre is used to indicate a plane perpendicular to the rotation axis of the tyre and and dividing the tyre into two equal portions.

[0059] 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.

[0060] 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.

[0061] 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 chord of the tyre, and the same maximum chord of the tyre, in a cross section of the tyre.

[0062] 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.

[0063] The term “annular portion” is used to indicate a portion of the tread band circumferentially extending for the entire tread band and having a predetermined axial extension. The distance of an annular portion of the tread band from the equatorial plane or the distance between annular portions of the tread band is evaluated axially by referring to the central plane parallel to the equatorial plane of the portion(s).

[0064] 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.

[0065] 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.

[0066] 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 centers of all possible circles, tangent to the walls of the groove or to the edges of the rib.

[0067] 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 °.

[0068] 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 °.

[0069] 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.

[0070] 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 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, proceeds up to the direction tangent to the groove or to the rib passing through such a point.

[0071] Thus, for example, and as will be better illustrated hereinafter, the aforementioned rotation is deemed to be carried out by a vector oriented in the direction of rotation of the tyre in the case of a rear tyre or by a vector oriented in a direction opposite to the direction of rotation of the tyre in the case of a front tyre.

[0072] 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.

[0073] When the groove comprises a plurality of 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.

[0074] When the groove comprises a plurality of 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.

[0075] 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 °.

[0076] 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.

[0077] The term “width” of the ribs defined between consecutive grooves is used to indicate the distance between facing edges of the aforementioned grooves. Such a dimension can for example be defined by the diameter of a circle tangent to the facing edges of consecutive grooves and inscribed between said grooves.

[0078] The term “pitch” of the tyre is used to indicate the group of grooves and rubber parts arranged so as to form a portion of the pattern, which is repeated 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 may have different circumferential lengths.

[0079] The term “substantially curvilinear” course of a groove is used to indicate a course with substantial continuity of the derivative of the curve representing the course itself. Typically, this is achieved by means of a course without sharp points. The present definition also includes the cases in which the groove is formed by or comprises a sequence of short straight sections, provided that the difference in the angular arrangement of such sections is not too large (e.g. equal to or greater than 25°).

[0080] The term “ground contacting area” of the tyre is used to indicate the portion of the 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.

[0081] 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.

[0082] Unless otherwise indicated, all the ranges of numerical entities also include the maximum and minimum numerical values.

[0083] 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 each another. 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.

[0084] 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, of high power both for road use and for track use of 1000 cm3displacement and more, with powers of 200 horsepower or even more.

[0085] 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 lower weight and displacement and used for training and / or recreational purposes on dedicated circuits.

[0086] 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 training and / or recreational purposes on track.

[0087] Preferably, the transversal grooves formed in the lateral annular portions of the tread band obliquely extend with respect to the equatorial plane of the tyre according to an angle of inclination comprised between 55° and 65° with respect to said equatorial plane.

[0088] In this way, it is advantageously possible to achieve optimal results in terms of improvement of the driving homogeneity and grip performance of the tyre in wet or humid conditions and / or in cold weather or non-optimal road surface conditions 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 performance of the tyre itself.

[0089] Preferably, the central annular portion of the tread band transversally extends along 10-25% of the axial development of the tread band.

[0090] In this way and as outlined above, it is advantageously possible to achieve, in all travel conditions of the motorcycle, optimal performances of water drainage, drivability, in particular contact feeling, and thrust improvement under acceleration of the tyre on a wet or humid surface and / or in cold weather or non- optimal road surface conditions.

[0091] Preferably, said transversal grooves have an axial extension comprised between 30% and 47%, more preferably comprised between 31 % and 38%, of the axial development of the tread band.

[0092] Preferably, said transversal ribs are substantially parallel to one another substantially along the entire axial extension thereof.

[0093] Preferably, said transversal ribs are substantially continuous for the entire axial extension thereof.

[0094] Preferably, said transversal ribs obliquely extend with respect to the equatorial plane of the tyre according to an angle of inclination comprised between 55° and 65° with respect to the equatorial plane of the tyre.

[0095] In this way, it is advantageously possible to achieve an optimal improvement of the thrust under acceleration of the tyre on a wet or humid surface and / or in cold weather or non-optimal road surface conditions.

[0096] Preferably, said at least one longitudinal groove is formed at, even more preferably astride of, the equatorial plane of the tyre.

[0097] Preferably, said at least one or said at least two longitudinal grooves have an axial extension comprised between 1 % and 8% of the axial development of the tread band.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] Preferably, the tread band comprises four longitudinal grooves, formed in the central annular portion thereof. Preferably, said four longitudinal grooves are symmetrically arranged on opposite sides with respect to the equatorial plane of the tyre.

[0102] Preferably, said four longitudinal grooves are arranged in two pairs symmetrically positioned on opposite sides with respect to the equatorial plane of the tyre.

[0103] Preferably, the tread band comprises a circumferential rib arranged astride of the equatorial plane of the tyre.

[0104] Preferably, this circumferential rib arranged astride of the equatorial plane of the tyre has an axial extension comprised between 5% and 16% of the axial development of the tread band.

[0105] In this way, it is advantageously possible to ensure an adequate axial stiffness of the tyre, i.e. an adequate stability and precision in the driving conditions along a straight course.

[0106] 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.

[0107] In this way, it is advantageously possible to achieve optimal performance in terms of water drainage under the ground contacting area of the tyre in combination with an adequate axial stiffness of the tyre, i.e. an adequate stability and precision in the driving conditions along a straight course, given by the circumferential ribs axially defined between the aforementioned longitudinal grooves.

[0108] 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.

[0109] In a corresponding way, 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.

[0110] In this way, it is advantageously possible to optimize the technical effect of ensuring, in all the driving conditions of the motorcycle, 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 rear tyre, to improve the thrust during acceleration of the tyre.

[0111] Preferably, said lateral annular portions of the tread band transversally extend along 70-95%, more preferably along 75-90%, of the axial development of the tread band.

[0112] In this way, it is advantageously possible to optimize the technical effect of ensuring, in all the travel conditions of the motorcycle, both an 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 rear tyre, to improve the thrust during acceleration of the tyre.

[0113] Preferably, the transversal grooves formed in the lateral annular portions of the tread band comprise a first substantially rectilinear axially inner portion and a second substantially rectilinear axially outer portion forming therebetween a vertex circumferentially oriented in the opposite direction or in the same direction with respect to the rolling direction of the tyre.

[0114] In this way, it is advantageously possible to mitigate the effects of the performance degradation of the tyre due to wearing.

[0115] Preferably, said first axially inner portion and said second axially outer portion of the transversal grooves form therebetween an angle at the vertex comprised between 165° and 179°.

[0116] 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.

[0117] In this way, it is advantageously possible to mitigate the effects of the performance degradation of the tyre due to wearing.

[0118] In an alternative preferred embodiment, the transversal grooves formed in the lateral annular portions of the tread band have a substantially curvilinear development forming a concavity circumferentially oriented in the opposite direction or in the same direction with respect to the rolling direction of the tyre.

[0119] In this way, it is advantageously possible to mitigate the effects of the performance degradation of the tyre due to wearing.

[0120] Preferably, the transversal grooves having a substantially curvilinear development are arranged at an average angle comprised between 40° and 75°, more preferably between 55° and 65°, with respect to the equatorial plane of the tyre.

[0121] In this way, it is advantageously possible to mitigate the effects of the degradation in performance of the tyre due to wearing.

[0122] Preferably, the transversal ribs formed in the lateral annular portions of the tread band are at least partially tapered in a direction from a shoulder portion of the tyre towards the equatorial plane of the tyre.

[0123] In this way, it is advantageously possible to impart an adequate continuity to the tread pattern between axially inner and axially outer portions 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.

[0124] Preferably, a ratio between a maximum width of the at least partially tapered transversal ribs formed in the lateral annular portions of the tread band measured at an axially outer end of said ribs and a minimum width measured at an axially inner end of said ribs is comprised between 1 and 1.25.

[0125] In this way, it is advantageously possible to keep the elastic shear characteristics of the tread band essentially constant.

[0126] Preferably, the transversal grooves formed in the lateral annular portions of the tread band comprise a plurality of sub-portions separated by a solid part of tread band.

[0127] In this way, it is advantageously possible to modulate the shear stiffness of the tread portion band present under the ground contacting area of the tyre.

[0128] 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.

[0129] 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.

[0130] Preferably, said 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.

[0131] 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.

[0132] Preferably, the transversal grooves formed in the lateral annular portions of the tread band have a width comprised between 2% and 10%, more preferably between 3.5% and 6% of an axial half-development of the tread band.

[0133] In this way, it is advantageously possible to optimize the technical effect of ensuring, in all the travel conditions of the motorcycle, both adequate water drainage and a continuity of interaction between the tyre and the road surface allowing to increase the grip with the latter and to improve the thrust during acceleration of the tyre.

[0134] Preferably, the transversal grooves formed in the lateral annular portions of the tread band are at least partially tapered in a direction from a shoulder portion of the tyre towards the equatorial plane of the tyre.

[0135] In this way, it is advantageously possible to impart an adequate continuity to the tread pattern between axially inner and axially outer portions 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.

[0136] Preferably, a ratio between a maximum width of the at least partially tapered transversal grooves formed in the lateral annular portions of the tread band measured at an axially outer end of said transversal grooves and a minimum width measured at an axially inner end of said transversal grooves is comprised between 1 and 1 .25. 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.

[0137] Preferably, said transversal ribs formed in the lateral annular portions of the tread band have a width comprised between 5% and 60% of an axial half-development of the tread band.

[0138] More preferably, said transversal ribs formed in the lateral annular portions of the tread band have a width comprised between 5% and 15% of an axial halfdevelopment of the tread band in the case of racing tyres (for example miniGP, Hypersport or Superbike).

[0139] More preferably, said transversal ribs formed in the lateral annular portions of the tread band have a width comprised between 15% and 60%, more preferably comprised between 30% and 60% of an axial half-development of the tread band in the case of tyres for road use.

[0140] In this way, it is advantageously possible to optimize the technical effect of ensuring, in all the travel conditions of the motorcycle, an adequate interaction between the tyre and the road surface allowing to increase the grip with the latter and to improve, in the case of a rear tyre, the thrust during acceleration of the tyre.

[0141] Preferably, a ratio between a width of the transversal grooves formed in the lateral annular portions of the tread band and a width of the transversal ribs formed between said transversal grooves, is comprised between 0.1 and 1 , preferably between 0.1 and 0.7.

[0142] In this way, it is advantageously possible to exploit the geometry of the pattern in wet conditions both for tyres for track use and for road use.

[0143] Preferably, the tyre is a tyre for a rear motorcycle wheel.

[0144] 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.

[0145] 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. Preferably, the tyre is a tyre for a front motorcycle wheel.

[0146] 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.

[0147] 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.

[0148] In a preferred embodiment, the tyre can have a nominal fitting diameter comprised between 10” and 18”.

[0149] 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” 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.

[0150] In a further preferred embodiment, the tyre can have a nominal fitting diameter comprised between 10” and 12”.

[0151] 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 a low weight (for example 60 to 90 kg), power (for example 15-25 horsepower) and displacement (for example 150 to 190 cc) and used for training and / or recreational purposes on dedicated circuits.

[0152] Brief description of the figures

[0153] Additional features and advantages of the invention will be better apparent from the following description of some preferred embodiments thereof, made hereinafter, for illustrative and not limiting purposes, with reference to the attached drawings.

[0154] Such drawings are schematic and not to scale.

[0155] In the drawings:

[0156] - figure 1 shows a perspective view of a rear motorcycle tyre according to a preferred embodiment of the invention;

[0157] - figure 2 is an enlarged view of a cross section of the tyre of figure 1 ; - figure 3 is a schematic plan view of a portion of the tread band of the tyre of figure 1 .

[0158] - figures 4-8 are schematic plan views of a portion of preferred alternative embodiments of the tread pattern of the rear tyre of figure 1 .

[0159] Detailed description of embodiments

[0160] In figures 1 -3, reference numeral 1 generally indicates a rear tyre for motorcycle wheels according to a first preferred embodiment of the present invention.

[0161] This embodiment concerns a rear tyre having a nominal fitting diameter comprised between 10” and 18”, preferably intended to be used on a wheel of a motorcycle for a Supersport motorbike having large displacement, for example 600cc.

[0162] An equatorial plane X-X and a rotation axis Z are defined in the tyre 1 (see figure 2).

[0163] A circumferential direction (indicated in figures 1 and 3 with the arrow F oriented in the direction of rotation of the tyre 1 ) and an axial direction perpendicular to the equatorial plane X-X are also defined.

[0164] The tyre 1 comprises a carcass structure 2 having a central crown portion 16 including at least one carcass ply 3, described hereinafter in greater detail.

[0165] The carcass structure 2 is preferably coated, on the inner walls thereof, by a sealing layer 1 1 , or so-called “liner”, essentially consisting of an airtight layer of elastomeric material, adapted to impart a hermetic seal to the tyre itself 1 once inflated.

[0166] The carcass ply 3 has its axially opposite lateral edges 3a facing respecting annular reinforcing structures 4 intended to hold the tyre 1 on a corresponding mounting rim. The annular reinforcing structures 4 are typically called “bead cores”.

[0167] The outer perimetral edge of the bead cores 4 has a tapered elastomeric filler 5 applied thereon, which occupies the space defined between the carcass ply 3 and the corresponding turned-up side edge 3a of the carcass ply 3.

[0168] 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.

[0169] The area of the tyre comprising the bead core 4 and the filling 5 forms the so- called “bead”, globally indicated in figure 1 with 15, intended for anchoring the tyre on a corresponding mounting rim, not illustrated.

[0170] A belt structure 6, also described in greater detail hereinafter, is provided at a radially outer position with respect to the aforementioned carcass structure 2.

[0171] A tread band 8, 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 6.

[0172] The tyre 1 can also comprise a pair of sidewalls 2a laterally applied to the carcass structure 2 on axially opposite sides with respect to the equatorial plane X-X. The sidewalls 2a extend from the tread band 8 to the bead 15 of the tyre 1 .

[0173] The tyre 1 of the present invention is distinguished by a high transversal curvature and low profile sidewalls 2a.

[0174] 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 8 from the line b-b passing through the ends 0 of the tread band 8, measured along the equatorial plane X-X, and the distance wt between the ends 0 of the tread band 8. 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 0, the measurement of the maximum cord, or maximum width of radial section, of the tyre 1 , may be taken as distance wt.

[0175] The tyre 1 of the present invention preferably has a transversal curvature ratio greater than or equal to 0.29 and lower than or equal to 0.35.

[0176] On the other hand, as far as the sidewalls 2a are concerned, the tyre 1 of the present invention is preferably a tyre with particularly 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 8 and the fitting diameter, identified by the reference line LR passing through the beads 15 of the tyre 1 , is lower than 0.65, more preferably lower than 0.6, for example equal to 0.55.

[0177] The carcass ply 3 is preferably made of elastomeric material and comprises a plurality of reinforcing elements (not illustrated) arranged parallel to one another and perpendicular to the equatorial plane.

[0178] The reinforcing elements included in the carcass ply 3 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 having a diameter comprised between 0.10 mm and 0.5 mm.

[0179] The belt structure 6 preferably comprises rubber-coated cords 7, arranged substantially parallel and side-by-side to each other in the axial direction on the crown portion 16 of the carcass structure 2, to form a plurality of coils 7a. Such coils 7a are substantially oriented according to the rolling direction of the tyre 1 (in particular at 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 16 of the carcass structure 2.

[0180] Preferably, the belt structure 6 comprises windings of a single cord 7, 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 16 of the carcass structure 2.

[0181] Preferably, such cords 7 are made of steel wires having a high carbon content (HT), i.e. steel wires with a carbon content greater than 0.9%.

[0182] Alternatively, the belt structure 6 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 oblique orientation, but symmetrically crossed with respect to the cords of the first layer, to form the so- called “crossed belt”. In this case, generally, the cords 7 of the belt structure 6 are generally textile cords, for example textile cords made of a synthetic fiber, for example nylon, rayon, PEN, PET, preferably made of a 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 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.

[0183] 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.

[0184] 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.

[0185] In both cases, the cords 7 of the belt structure 6 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 a synthetic fiber having a high modulus, in particular synthetic aramid fiber (aromatic polyamides).

[0186] Preferably, the belt structure 6 comprises a support layer 9 substantially consisting of a sheet of elastomeric material arranged between the layer of cords 7 and the carcass ply 3 and on which the coils 7a are wound. The layer 9 preferably extends over a surface having an axial extension substantially corresponding to the surface on which the coils 7a develop. Alternatively, the layer 9 can extend over a surface smaller than the development surface of the coils 7a, for example only over opposite lateral portions of the belt structure 6.

[0187] In a further embodiment, not illustrated, an additional layer of elastomeric material is arranged between the belt structure 6 and the tread band 8. Such a layer preferably extends over a surface corresponding to the development surface of the belt structure 6. Alternatively, the aforementioned additional layer can extend over a surface smaller than the development surface of the belt structure 6, for example only over opposite lateral portions of the belt structure 6.

[0188] In a preferred embodiment of the tyre 1 of the present invention, at least one of the layer 9 and the aforementioned additional layer comprises short aramid fibers, for example made of Kevlar®, dispersed in the elastomeric material.

[0189] The tread band 8 has a tread pattern defined by a plurality of grooves formed on the outer surface of the tread band 8 by means of a molding operation carried out simultaneously with the vulcanization of the tyre 1 .

[0190] 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 thrust during acceleration on a wet or cold road surface at all camber angles of the tyre 1 keeping at the same time the wear characteristics thereof substantially unchanged.

[0191] In the present description and in the following claims, all the quantities of the elements of the tread band 8 are indicated and are deemed to be measured with reference to the plan development of the tread band itself.

[0192] The tread pattern of the tyre 1 comprises a modulus T repeated along a circumferential direction of the tyre 1 .

[0193] In the tyre 1 of the invention the modulus T corresponds to the portion of tread band 8 that, in the plan development illustrated in figure 3, is circumferentially delimited by the two broken lines ti and t2.

[0194] As better illustrated in figure 3, in which all the quantities - as indicated above - are measured in the plan development of the tread band 8, the modulus T has a circumferential length, indicated with C1 , and an axial development equal to the axial development L of the tread band 8.

[0195] In the preferred embodiment illustrated in figures 1 -3, the tread band 8 of the tyre 1 comprises a central annular portion L1 arranged astride of the equatorial plane X-X of the tyre 1 .

[0196] In the preferred embodiment illustrated in figures 1 -3, the central annular portion L1 of the tread band 8 is axially delimited by the axially outer wall of the axially outermost longitudinal groove 20 of the aforementioned plurality of longitudinal grooves 20.

[0197] Preferably, the central annular portion L1 of the tread band 8 transversally extends along 5-30%, more preferably along 10-25%, of the axial development L of the tread band 8.

[0198] Preferably, in the central annular portion L1 a pair of longitudinal grooves 20, symmetrically arranged on opposite sides with respect to the equatorial plane X- X of the tyre 1 , is formed.

[0199] In a preferred alternative embodiment, not illustrated, the tread band 8 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 .

[0200] Preferably, the longitudinal grooves 20 have an axial extension comprised between 1 % and 8% of the axial development L of the tread band 8.

[0201] 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 .

[0202] Preferably, the circumferential rib 21 arranged astride of the equatorial plane X- X of the tyre 1 has an axial extension comprised between 5% and 16% of the axial development L of the tread band 8.

[0203] In a further alternative preferred embodiment, not illustrated, the tread band 8 can comprise a longitudinal groove 20 formed astride of the equatorial plane X-X of the tyre 1 .

[0204] In a further alternative preferred embodiment, not illustrated, the tread band 8 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.

[0205] In the preferred embodiment illustrated in figures 1 -3, the tread band 8 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 the tyre 1 .

[0206] Preferably, the lateral annular portions L2, L3 of the tread band 8 transversally extend along 70-95%, more preferably along 75-90%, of the axial development L of the tread band 8. In each of the lateral annular portions L2, L3 of the tread band 8 a plurality of transversal grooves 33 is formed obliquely extending with respect to the equatorial plane X-X of the tyre 1 and having a directrix “g”, in this case substantially rectilinear, which represents the development thereof along the main direction thereof.

[0207] Preferably, the transversal grooves 33 form an angle of inclination alpha, measured as defined above, comprised between 40° and 75°, preferably between 55° and 65°, with respect to the equatorial plane X-X.

[0208] Preferably, the transversal grooves 33 have an axial extension equal to at least 30%, more preferably an axial extension comprised between 30% and 47%, even more preferably an axial extension comprised between 31 % and 38%, of the axial development L of the tread band 8.

[0209] Preferably, the transversal grooves 33 formed in the lateral annular portions L2, L3 of the tread band 8 have a width comprised between 2% and 10%, more preferably between 3.5% and 6%, of an axial half-development L / 2 of the tread band.

[0210] Preferably, the transversal grooves 33 are substantially parallel to one another substantially for their entire axial extension and are arranged according to a circumferential succession configured so as to form between the transversal grooves 33 a circumferential succession of transversal ribs 34 extending up to the axial ends of the tread band 8.

[0211] Preferably, the transversal ribs 34 are substantially continuous for the entire axial extension thereof.

[0212] Preferably, the transversal ribs 34 are substantially parallel to one another substantially along the entire axial extension thereof.

[0213] Preferably, the transversal ribs 34 have a substantially constant width.

[0214] Preferably and as outlined above, the transversal ribs 34 formed in the lateral annular portions L2, L3 of the tread band 8 have a width comprised between 5% and 60% of an axial half-development L / 2 of the tread band 8.

[0215] As outlined above, the width of the ribs 34 can for example be defined by the diameter of a circle tangent to the facing edges of circumferentially consecutive transversal grooves 33 and inscribed between said grooves. Such a circle, indicated with the reference letter C is illustrated purely as an example in figure 3.

[0216] Preferably, the transversal ribs 34 obliquely extend with respect to the equatorial plane X-X of the tyre 1 according to a same angle of inclination alpha of the transversal grooves 33, i.e. an angle of inclination comprised between 40° and 75°, preferably between 55° and 65°, with respect to the equatorial plane X-X.

[0217] Preferably, an axially inner end 33a of the transversal grooves 33 formed in the lateral annular portions L2, L3 of the tread band 8 is arranged at a predetermined distance “d” from an axially outermost longitudinal groove 20 of the longitudinal grooves 20 formed in the central annular portion L1 of the tread band 8.

[0218] In this way, a circumferential solid portion 35 of tread band is defined in the tread band 8 which is axially arranged between the axially outermost longitudinal groove 20 of the longitudinal grooves 20 and the axially inner end 33a of the transversal grooves 33 formed in the lateral annular portions L2, L3 of the tread band 8.

[0219] Preferably, the circumferential solid portion 35 of tread band is integral with the transversal ribs 34 formed in the lateral annular portions L2, L3 of the tread band 8.

[0220] Preferably, the distance “d” between said axially inner end 33a of the transversal grooves 33, formed in the lateral annular portions L2, L3 of the tread band 8 and the axially outermost longitudinal groove 20 of the longitudinal grooves 20 formed in the central annular portion L1 of the tread band 8, is comprised between 1 and 9% of the axial half-development L / 2 of the tread band 8.

[0221] In a corresponding manner, therefore, the circumferential solid portion 35 of tread band 8 axially arranged between the axially outermost longitudinal groove 20 and the axially inner end 33a of the transversal grooves 33 has an axial extension, identifiable with the aforementioned distance “d”, comprised between 1 and 9% of the axial half-development L / 2 of the tread band 8.

[0222] Preferably, a ratio between a width of the transversal grooves 33 formed in the lateral annular portions L2, L3 of the tread band 8 and a width of the transversal ribs 34 formed between the transversal grooves 33, is comprised between 0.1 and 0.7.

[0223] In a preferred embodiment, not illustrated, the transversal grooves 33 formed in the lateral annular portions L2, L3 of the tread band 8 can be 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 .

[0224] Preferably, a ratio between a maximum width of the at least partially tapered transversal grooves 33 measured at an axially outer end of the transversal grooves 33 and a minimum width measured at an axially inner end of said transversal grooves 33 is comprised between 1 and 1.25.

[0225] Preferably, a ratio between a maximum width of the at least partially tapered transversal ribs 34 formed in the lateral annular portions L2, L3 of the tread band 8 measured at an axially outer end of said ribs 34 and a minimum width measured at an axially inner end of said ribs 34 is comprised between 1 and 1.25.

[0226] With reference to figures 4-8, additional preferred embodiments of the tread pattern of the tyre 1 according to the invention will now be described.

[0227] 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.

[0228] In the embodiment of figure 4, a variant of the tread pattern 8 is illustrated in which the transversal grooves 33 formed in the lateral annular portions L2, L3 of the tread band 8 comprise a first substantially rectilinear axially inner portion 33’ and a second substantially rectilinear axially outer portion 33” and forming therebetween a vertex V circumferentially oriented in the opposite direction with respect to the rolling direction F of the tyre 1 .

[0229] Preferably, the first axially inner portion 33’ and the second axially outer portion 33” of the transversal grooves 33 form therebetween an angle beta at the vertex comprised between 165° and 179°.

[0230] In other words, the second axially outer portion 33” of the transversal grooves 33 forms an angle comprised between 1 ° and 15° with the first axially inner portion 33’.

[0231] In this preferred embodiment, the transversal ribs 34 formed in the lateral annular portions L2, L3 of the tread band 8 are 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 . More particularly, an axially outer portion 34” of the transversal ribs 34 defined between the second axially outer portion 33” of circumferentially consecutive transversal grooves 33 is tapered in a direction from a shoulder portion of the tyre 1 towards the equatorial plane X-X of the tyre 1 .

[0232] Preferably, a ratio between a maximum width of the tapered axially outer portion 34” and a width of an axially inner portion 34’, not tapered, of the transversal ribs 34 is comprised between 1 and 1.25.

[0233] In the embodiment of figure 5, a variant of the tread pattern is illustrated in which the transversal grooves 33 formed in the lateral annular portions L2, L3 of the tread band 8 have a substantially curvilinear development along the directrix g thereof.

[0234] Preferably, the transversal grooves 33 having a substantially curvilinear development form a concavity circumferentially oriented in the opposite direction with respect to the rolling direction F of the tyre 1 .

[0235] Preferably, the transversal grooves 33 having a substantially curvilinear development are arranged at an average angle comprised between 40° and 75°, more preferably between 55° and 65°, with respect to the equatorial plane X-X of the tyre 1 .

[0236] In this preferred embodiment, the transversal ribs 34 having a substantially curvilinear development formed in the lateral annular portions L2, L3 of the tread band 8 are tapered in a direction from a shoulder portion of the tyre 1 towards the equatorial plane X-X of the tyre 1 .

[0237] Preferably, a ratio between a maximum width of the tapered transversal ribs 34 having a substantially curvilinear development formed in the lateral annular portions L2, L3 of the tread band 8 measured at an end of said ribs 34 and a minimum width measured at an axially opposite end of said ribs 34 is comprised between 1 and 1 .25.

[0238] In the embodiments of figures 6-8, variants of the tread pattern 8 are illustrated in which the transversal grooves 33 formed in the lateral annular portions L2, L3 of the tread band 8 comprise a plurality of sub-portions separated by solid parts 36 of tread band.

[0239] Preferably, the solid parts 36 have a length, measured along a directrix g of the transversal grooves 33 not greater than 25% preferably comprised between 2.5% and 25%, of the total length of the transversal grooves 33 measured along said directrix (g).

[0240] In figure 6, a first variant is illustrated in which each groove 33 comprises three sub-portions separated by two solid parts 36 of tread band.

[0241] In this preferred embodiment, the groove 33 comprises - more particularly - a central sub-portion 33b' and two lateral sub-portions 33b" arranged at axially opposite sides of the central sub-portion 33b'.

[0242] In this preferred embodiment, the groove 33 can have a substantially curvilinear development along the directrix g thereof, forming a concavity circumferentially oriented in the opposite direction with respect to the rolling direction F of the tyre 1.

[0243] Preferably, the curvature characteristics of the groove 33 can be analogous to those described earlier with reference to the preferred embodiment illustrated in figure 5.

[0244] In this case, therefore, the central sub-portion 33b' and the two lateral subportions 33b" can have a substantially curvilinear development.

[0245] In figure 7, a second variant is illustrated in which each groove 33 comprises two sub-portions 33b'" having a same length separated by a solid part 36 of tread band.

[0246] In figure 8, a third variant is illustrated in which each groove 33 comprises two sub-portions 33b'v, 33bvhaving different lengths, separated by a solid part 36 of tread band.

[0247] Purely as an example, in figure 8 the axially outer sub-portion 33b'vhas a greater length than the axially inner sub-portion 33bv. Equally applicable for the purposes of the invention is an opposite configuration in which the axially outer sub-portion 33b'vhas a shorter length than the axially inner sub-portion 33bv.

[0248] Finally, also in the preferred embodiments illustrated in figures 7 and 8, the groove 33 can have a substantially curvilinear development along the directrix g thereof, forming a concavity circumferentially oriented in the opposite direction with respect to the rolling direction F of the tyre 1 .

[0249] Preferably, the curvature characteristics of the groove 33 can also in this case be analogous to those described earlier with reference to the preferred embodiment illustrated in figure 5.

[0250] The invention will now be illustrated by means of some Examples to be considered for illustrating and not limiting purposes thereof.

[0251] Outdoor tests on tyres

[0252] The Applicant, with a view to improving the constancy of performance as the camber angle of the tyre changes even up to full bend driving conditions, took as base of the comparative driving test the tyre for a rear wheel made by Pirelli model Diablo Rain® that was and still is a reference tyre that is highly appreciated by sports users.

[0253] Different test sessions were carried out in a private racetrack, carrying out a series of maneuvers to test traction and maneuverability on wet ground. The driver’s evaluation is an average of the evaluations attributed in the various maneuvers.

[0254] In the test on wet ground the conditions were: tyre inflation pressure 1 .9 bar; temperature of the asphalt of the track 23°C; air temperature 21 °C.

[0255] The tests were carried out with motorcycles of the “Super sport” segment model YAMAHA R1 M and BMW S 1000 RR STOCK.

[0256] The following Table 1 summarizes the marks given by the test driver in the tests on wet ground, for the various types of performance required of the tested tyre (average of the evaluations of two test drivers on the motorcycles indicated above).

[0257] 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.

[0258] Table 1

[0259] The results given in Table 1 demonstrate that the tyre according to the invention has shown an improved behavior with respect to the already excellent comparative tyre on a wet ground both in terms of traction, and maneuverability, also for bend angles typically not reached on wet road surfaces. From the tests carried out in particular two groups of improved performance became available.

[0260] A first group, characterized by the driving quality (in the table indicated in the section “driving fundamentals”) and by the safety feeling, i.e. by characteristics which allow to drive by selecting different trajectories safely, and thus be able to maneuver in an optimal manner in race conditions.

[0261] 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 in the travel conditions along a straight course, and when increasing the camber angle (i.e. entering or exiting a bend). A second group, correlated with peak performance in the various camber angles tackled (in the table indicated in the “drainage” and “traction” sections).

[0262] Without wishing to be bound also in this case by any interpretative theory, 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 in the travel conditions along a straight course, and when increasing the camber angle (i.e. entering or exiting a bend).

[0263] During the tests carried out it was also found that with the tyres according to the invention there were significant reductions in the lap times on the test racetracks.

[0264] 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

CLAIMS1 . Motorcycle tyre (1 ), comprising an equatorial plane (X-X) and a tread band (8) extending according to an axial development (L), wherein the tread band (8) comprises, in a plan development thereof:- a central annular portion (L1 ) arranged astride of the equatorial plane (X-X) of the tyre (1 );- 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 the tyre (1 );- at least one longitudinal groove (20) formed in the central annular portion (L1 ) of the tread band (8) or at least two longitudinal grooves (20) formed in the central annular portion (L1 ) and arranged, preferably symmetrically, on opposite sides with respect to the equatorial plane (X-X) of the tyre (1 );- a plurality of transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) and obliquely extending with respect to the equatorial plane (X-X) of the tyre (1 ) according to an angle of inclination comprised between 40° and 75°, preferably between 55° and 65° with respect to said equatorial plane (X-X), wherein the central annular portion (L1 ) of the tread band (8) transversally extends along 5-30%, preferably along 10-25%, of the axial development (L) of the tread band (8); wherein said transversal grooves (33) have an axial extension equal to at least 30%, preferably an axial extension comprised between 30% and 47%, more preferably an axial extension comprised between 31 % and 38%, of the axial development (L) of the tread band (8); wherein said transversal grooves (33) are substantially parallel to one another substantially for their entire axial extension and are arranged according to a circumferential succession configured so as to form between the transversal grooves (33) a circumferential succession of transversal ribs (34) extending up to the axial ends of the tread band; wherein said transversal ribs (34) have a substantially constant width and obliquely extend with respect to the equatorial plane (X-X) of the tyre (1 ) according to said angle of inclination comprised between 40° and 75°, preferablybetween 55° and 65° with respect to said equatorial plane (X-X); wherein an axially inner end (33a) of the transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) 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), formed in the central annular portion (L1 ) of the tread band (8), so as to form a circumferential solid portion (35) of tread band (8) axially arranged between said axially inner end (33a) of the transversal grooves (33) and said at least one longitudinal groove (20), or said axially outermost longitudinal groove (20) of said at least two longitudinal grooves (20); and wherein said circumferential solid portion (35) of tread band (8) is integral with said transversal ribs (34) formed in the lateral annular portions (L2, L3) of the tread band (8).

2. Motorcycle tyre (1 ) according to claim 1 , wherein said at least one longitudinal groove (20) is formed at, preferably astride of, the equatorial plane (X-X) of the tyre (1 ).

3. Motorcycle tyre (1 ) according to any one of the preceding claims, 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 development (L) of the tread band (8).

4. Motorcycle tyre (1 ) according to claim 1 , 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 ).

5. Motorcycle tyre (1 ) according to claim 4, wherein the tread band (8) comprises 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 ).

6. Motorcycle tyre (1 ) according to claim 4 or 5, wherein said circumferential rib (21 ) arranged astride of the equatorial plane (X-X) of the tyre (1 ) has an axial extension comprised between 5% and 16%, of the axial development (L) of the tread band (8).

7. Motorcycle tyre (1 ) according to claim 2, wherein the tread band (8) further comprises two longitudinal grooves (20) formed in the central annular portion (L1 ) and symmetrically arranged on opposite sides with respect to said longitudinal groove (20) formed at, preferably astride of, the equatorial plane (X-X) of the tyre (1 ).

8. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein said distance (d) between said axially inner end (33a) of the transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) and said at least one longitudinal groove (20), or an axially outermost longitudinal groove (20) of said at least two longitudinal grooves (20) formed in the central annular portion (L1 ) of the tread band (8), is comprised between 1 % and 9% of an axial half-development (L / 2) of the tread band (8).

9. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein said lateral annular portions (L2, L3) of the tread band (8) transversally extend along 70%-95%, preferably along 75%-90% of the axial development (L) of the tread band (8).

10. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) comprise a first substantially rectilinear axially inner portion (33’) and a second substantially rectilinear axially outer portion (33”) forming therebetween a vertex (V) circumferentially oriented in the opposite direction or in the same direction with respect to the rolling direction (F) of the tyre (1 ).

11. Motorcycle tyre (1 ) according to claim 10, wherein said first axially inner portion (33’) and said second axially outer portion (33”) of the transversal grooves (33) form therebetween an angle at the vertex (beta) comprised between 165° and 179°.

12. Motorcycle tyre (1 ) according to any one of claims 1 -9, wherein the transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) have a substantially curvilinear development forming a concavity circumferentially oriented in the opposite direction or in the same direction with respect to the rolling direction (F) of the tyre (1 ).

13. Motorcycle tyre (1 ) according to claim 12, wherein said transversal grooves (33) having a substantially curvilinear development are arranged at an average angle comprised between 40° and 75°, preferably between 55° and 65°,with respect to said equatorial plane (X-X).

14. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein said transversal ribs (34) formed in the lateral annular portions (L2, L3) of the tread band (8) are 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 ).

15. Motorcycle tyre (1 ) according to claim 14, wherein a ratio between a maximum width of the at least partially tapered transversal ribs (34) formed in the lateral annular portions (L2, L3) of the tread band (8) measured at an axially outer end of said ribs (34) and a minimum width measured at an axially inner end of said ribs (34) is comprised between 1 and 1.25.

16. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) comprise a plurality of sub-portions (33b) separated by a solid part (36) of tread band, and wherein each solid part (36) has a length, measured along a directrix (g) of said transversal grooves (33), not greater than 25% preferably comprised between 2.5% and 25%, of the total length of the transversal grooves (33) measured along said directrix (g).

17. Motorcycle tyre (1 ) according to claim 16, wherein said sub-portions (33b) of the transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) have a length, measured along the directrix (g) of said transversal grooves (33), comprised between 20% and 75% of the total length of the transversal grooves (33).

18. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) have a width comprised between 2% and 10%, preferably between 3.5% and 6% of an axial half-development (L / 2) of the tread band (8).

19. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) are 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 ).

20. Motorcycle tyre (1 ) according to claim 19, wherein a ratio between a maximum width of the at least partially tapered transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) measured at an axially outer end of said transversal grooves (33) and a minimum width measured at anaxially inner end of said transversal grooves (33) is comprised between 1 and 1.25.21 . Motorcycle tyre (1 ) according to any one of the preceding claims, wherein said transversal ribs (34) formed in the lateral annular portions (L2, L3) of the tread band (8) have a width comprised between 5% and 60% of an axial halfdevelopment (L / 2) of the tread band (8).

22. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein a ratio between a width of the transversal grooves (33) formed in the lateral annular portions (L2, L3) of the tread band (8) and a width of the transversal ribs (34) formed between said transversal grooves (33), is comprised between 0.1 and 1 , preferably between 0.1 and 0.7.

23. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the tyre is a tyre for a rear wheel.

24. Motorcycle tyre (1 ) according to claim 23, wherein the tyre 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.

25. Motorcycle tyre (1 ) according to any one of claims 1 -22, wherein the tyre is a tyre for a front wheel.

26. Motorcycle tyre (1 ) according to claim 25, wherein the tyre 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.

27. Motorcycle tyre (1 ) according to any one of the preceding claims, wherein the tyre has a nominal fitting diameter comprised between 10” and 18” or a nominal fitting diameter comprised between 10” and 12”.

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