Motorcycle tyre

Abstract

A motorcycle tyre comprises a tread band having a central annular portion (A) extending astride of an equatorial plane (X-X) of the tyre and two lateral annular portions arranged on opposite sides with respect to the central annular portion (A). The central annular portion (A) comprises a plurality of circumferential grooves (20; 60) each having an intermediate portion (21; 61) and two end portions (22, 23; 62, 63) arranged on opposite sides with respect to the intermediate portion (21; 61) along a circumferential direction. The intermediate portion (21; 61) has a width (W1a) less than the maximum width (W1b, W1c) of each of the two end portions (22, 23; 62, 63).

Description

[0001] Motorcycle tyre

[0002] DESCRIPTION

[0003] The present invention relates to a motorcycle tyre.

[0004] The tyre of the invention is intended to equip the front and rear wheels of motorcycles of the "Sport Touring" segment, which as known are motorcycles with large displacement (for example 800 cm3or higher), and / or medium / high power (for example 60 / 80 horsepower or higher) capable of reaching speeds even higher than 180 km / h and of withstanding maximum loads even higher than 200 kg.

[0005] Some examples of "Sport Touring" motorcycles are: Kawasaky Versys 1000, BMW S1000XR, Ducati Multistrada V4 Rally.

[0006] PRIOR ART

[0007] Motorcycle tyres of the "Sport Touring" segment typically comprise a tread band having a tread design defined by a plurality of circumferential and transversal grooves. Examples of such tyres are described in WO 2020 / 110075 and WO 2020 / 110080 of the Applicant.

[0008] WO 2021 / 090152 of the Applicant describes an example of a tyre suitable for equipping both motorcycles of the "Sport Touring" segment and motorcycles of the "Supersport" segment.

[0009] SUMMARY OF THE INVENTION

[0010] Throughout this description and in the following claims, when reference is made to any range of values comprised between a minimum value and a maximum value, the aforementioned minimum and maximum values are deemed to be included in the range, unless expressly stated to the contrary.

[0011] Moreover, all of the ranges include any combination of the described minimum and maximum values and include any intermediate range, even if not expressly described specifically.

[0012] Even if not expressly indicated, any numerical value is deemed to be preceded by the term "about" to also indicate any numerical value that differs slightly from the one described, for example to take into account the dimensional tolerances typical of the field of reference.

[0013] Hereinafter, the following definitions apply.

[0014] The term "motorcycle tyres" is used to indicate a tyre having a high curvature ratio (typically greater than 0.20) and capable of reaching high camber angles when cornering.

[0015] The term "curvature ratio" is used to indicate the ratio of the distance comprised between the radially highest point of the tread band and the maximum cord of the tyre (this distance being also identified as "arrow"), and the maximum cord of the tyre itself, in a cross section of the tyre.

[0016] The term "maximum cord" or "radial section maximum width" is used to indicate the maximum width of the tyre profile, i.e. the length of the segment having as its ends the two axially outermost points of the tread band.

[0017] The term "footprint area" of the tyre is used to indicate the portion of the tyre in contact with the ground or road surface when the tyre is mounted on a wheel rim and a predetermined vertical load is exerted on the tyre.

[0018] The term "contact forces" is used to indicate the forces that are transferred between the tyre and the ground or road surface or asphalt at the footprint area during the rolling of the tyre.

[0019] 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 symmetrically equal parts.

[0020] The term "tread pattern" is used to indicate the representation of all the points of the tread band (including the grooves) on a plane perpendicular to the equatorial plane of the tyre and tangent to the maximum diameter of the tyre. This representation corresponds to the plan development of the outermost profile of the tread band.

[0021] The measurements of linear quantities (distances, widths, lengths, axial and circumferential extensions, etc.) and / or angles are to be understood as referred to the tread pattern as defined above.

[0022] The term "circumferential development" of the tyre, or of the tread band or of portions thereof, is used to indicate the plan development of the radially outermost surface of the tyre, or of the tread band or of portions thereof, on a plane tangent to the tyre.

[0023] The term "void to solid ratio" is used to indicate the ratio of the overall surface of the grooves of a determined annular portion of the tread band or of a determined portion of the tread pattern of the tyre (possibly of the entire tread band or of the entire tread pattern) and the surface of the determined annular portion of the tread band or of the determined portion of tread pattern (possibly of the entire tread band or of the entire tread pattern).

[0024] The term "amount" of voids is used to indicate the total area occupied by the grooves, or by portions of grooves, which are in the tread band. This area depends on the number and dimensions of the grooves, or of the portions thereof.

[0025] The term "annular portion" of a tread band is used to indicate a portion of the tread band extending circumferentially along the whole tread band and having a predetermined width.

[0026] The terms "radial" and "axial" and the expressions "radially inner / outer" and "axially inner / outer" are used with reference to a direction substantially parallel to the equatorial plane of the tyre and to a direction substantially perpendicular to the equatorial plane of the tyre, respectively, i.e. to a direction substantially perpendicular to the rotation axis of the tyre and to a direction substantially parallel to the rotation axis of the tyre, respectively.

[0027] The expressions "axially inner" and "axially outer" indicate a position closer to, and farther from, the equatorial plane with respect to a reference element, respectively. Thus, for example, a first groove portion is axially inner with respect to a second groove portion when the axial distance of the first groove portion from the equatorial plane is less than that of the second groove portion. Similarly, a first groove portion is axially outer with respect to a second groove portion when the axial distance of the first groove portion from the equatorial plane is greater than that of the second groove portion.

[0028] The terms "circumferential" and "circumferentially" are used with reference to the direction of circumferential development of the tyre, i.e. to the rolling direction of the tyre, which corresponds to a direction lying on a plane coinciding with or substantially parallel to the equatorial plane of the tyre.

[0029] The term "circumferential groove" is used to indicate a groove that extends along a trajectory substantially parallel to the equatorial plane.

[0030] The expression "substantially parallel" indicates not only a condition of perfect parallelism, but also a condition diverging from the perfect parallelism by an angle not higher than 20°, preferably not higher than 15°.

[0031] The term "transversal groove" is used to indicate a groove that extends along a trajectory inclined with respect to the equatorial plane by an angle greater than 20°, preferably, greater than 25°, even more preferably greater than 30°. In the case of grooves having a substantially curvilinear or generally non-rectilinear extension, the line that joins the two opposite ends of the groove is considered for the measurement of the angle of inclination.

[0032] The term "substantially curvilinear extension" is used to indicate a development having a substantial continuity of the derivative of the curve that represents the development itself. Typically, a substantially curvilinear extension is devoid of angular points. However, this definition also includes cases in which the development is obtained through a succession of short rectilinear segments, provided that the angle difference between these segments is less than 20°.

[0033] Hereinafter, a groove, or a portion thereof, is considered "circumferentially offset" with respect to another groove, or to a portion thereof, when the circumferentially central points of the two grooves, or of the respective portions, do not lie on a same plane perpendicular to the equatorial plane of the tyre.

[0034] A groove, or a portion thereof, is instead considered "superimposed in the axial direction" on another groove, or on a portion thereof, when the projections on the equatorial plane of the two grooves, or of the respective portions, are at least in part superimposed on each other. In such a case, the projection on the equatorial plane of at least a segment of each of the two grooves is identical to that of at least a segment of the other groove.

[0035] With reference to the angle of the grooves or of portions thereof with respect to the equatorial plane of the tyre, this angle is to be understood, for each point of the groove or of the portion thereof, as the angle, in absolute value, formed by performing a rotation which, 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 portion thereof passing through said point. In the case of a tyre intended to be mounted on a rear wheel of a motorcycle, the aforementioned rotation is to be understood as performed by a vector oriented in the opposite direction to the direction of rotation of the tyre, while in the case of a tyre intended to be mounted on a front wheel of a motorcycle, the aforementioned rotation is to be understood as performed by a vector oriented in the direction of rotation of the tyre.

[0036] A surface or face is "concave" with respect to the equatorial plane of the tyre if an intermediate portion thereof is farther from the equatorial plane than the end portions thereof.

[0037] A surface or face is "convex" with respect to the equatorial plane of the tyre if an intermediate portion thereof is closer to the equatorial plane than at least one of the end portions thereof.

[0038] The term "width" is used to indicate a dimension measured along a direction orthogonal to the equatorial plane.

[0039] The term "width" of a groove, or of a portion thereof, is used to indicate a dimension measured along a direction orthogonal to the trajectory along which the groove, or the portion thereof, extends.

[0040] The term "length" of a groove, or of a portion thereof, is used to indicate the length of the groove, or of the portion thereof, measured along the trajectory along which the groove, or the portion thereof, extends.

[0041] The term "circumferential extension" of a groove, or of a portion thereof, is used to indicate the length of the projection of the groove, or of the portion thereof, on a plane parallel to the equatorial plane.

[0042] The Applicant has observed that there are Sport Touring motorcycles on the market with particularly high piston displacements and powers, for example a piston displacement equal to 1000 cm3or beyond and powers equal to 180 horsepower or beyond.

[0043] The Applicant has considered that the users of such motorcycles wish to equip their own motorcycles with tyres capable of achieving not only the performances typically required to the tyres for Sport Touring motorcycle in terms of mileage, comfort, driveability, stability and grip on road surfaces, whether regular or not and whether dry or wet, even in difficult weather conditions, such as cold, but also performances under conditions of particularly high speed and particularly extreme manoeuvres, such as for example accentuated bends during cornering.

[0044] The Applicant has thought about how to improve the performances on the dry surface of a tyre for Sport Touring motorcycle with high piston displacement and power in terms of driveability, grip and stability with respect to those offered by the tyres of the same segment currently on the market (hereinafter referred to as "reference tyres"), so as to allow an even sportier driving, tending towards the one allowed by the motorcycle tyres in the "Supersport" segment.

[0045] However, the Applicant has also considered the objective of not penalising performances on the wet surface with respect to those offered by the reference tyres.

[0046] The Applicant has observed that, whatever the segment to which the tyre belongs, its performances on the dry surface improve as the capacity of the tyre to adhere to the road surface increases, this capacity being the greater the smaller the number and / or the dimensions of the grooves which are in the footprint area while the tyre is travelling in a rectilinear line and is bending.

[0047] Therefore, according to the Applicant, one way to achieve the desired improvement of the performances on the dry surface of a tyre for Sport Touring motorcycle would be to reduce the amount of voids which are in the footprint area.

[0048] However, the Applicant has observed that a reduction in the amount of voids in the footprint area would result in a worsening of the performances on the wet surface with particular regard to water drainage, a circumstance that would be in contrast with the intention of having performances on the wet surface at least equal to those of the reference tyres.

[0049] The Applicant has thought about on how to overcome this impasse situation and has thought that it would be desirable to have a tread design that, at the portion of the tread band that during the rolling of the tyre is in the footprint area, is able to "change" configuration as a function of the conditions of the road surface on which the tyre is rolling, so as to switch from a first configuration in which there is an ideal amount of voids to achieve excellent performances of the tyre both on the dry and on the wet surface, to a second configuration in which there is an amount of voids deemed ideal to achieve the desired improvement in the performances on the dry surface while maintaining those on the wet surface.

[0050] The Applicant has considered that when the tyre is travelling on the dry surface the contact forces are higher than those when the tyre is travelling on the wet surface. Consequently, the deformation of the tread band in the footprint area while travelling on the dry surface is greater than while travelling on the wet surface.

[0051] The Applicant has perceived that it is possible to obtain a tread design capable of "changing" as described above by providing, in at least some of the grooves which are in the footprint area, at least a portion having a reduced width that is configured to close when the contact forces are sufficiently high, as in cases where the tyre is travelling on the dry road surfaces, and that instead remains open when the contact forces are more reduced, as in cases where the tyre is travelling on wet road surfaces. The closing of the grooves at the aforementioned portions having a reduced width in fact entails a temporary reduction in the amount of voids in the footprint area; this occurs when the tyre is travelling on the dry surface and it is beneficial to the grip. The subsequent reopening of the grooves at the aforementioned portions having a reduced width results in the initial amount of voids being restored; this occurs when the tyre is travelling on the wet surface and it is beneficial to the water drainage.

[0052] The Applicant has considered that, in order not to incur unwanted phenomena of excessive and / or irregular wear of the tread band, it is advantageous that at least some of the grooves which are in the central annular portion of the tread band are oriented along a substantially circumferential direction, so as to avoid having, at least at these grooves, groove edges oriented transversely with respect to the forces to which the tyre is subjected during accelerations and braking.

[0053] Wishing to tend towards the performances on dry surface offered by the motorcycle tyres of the "Supersport" segment, such as for example the one described in WO 2021 / 090152, and having observed that these performances are positively influenced by the fact that the tread band of such tyres has, in the central annular portion thereof, tread band portions having a high circumferential extension and provided with circumferential grooves that alternate along the circumferential direction to tread band portions having a reduced circumferential extension and free of grooves, the Applicant has considered it appropriate to adopt a similar alternation in the circumferential direction also in the tyres of the invention.

[0054] The Applicant has therefore thought that in order to achieve all the purposes discussed above, it is advisable that the portions having a reduced width are provided precisely in the aforementioned circumferential grooves and, more precisely, in a circumferentially intermediate portion of the aforementioned grooves, so as to have in the circumferential direction an alternation between tread band portions having a high circumferential extension and provided with circumferential grooves and tread band portions having a reduced circumferential extension and free of grooves similar to the one of the aforementioned motorcycle tyre of the "Supersport" segment.

[0055] The present invention therefore relates to a motorcycle tyre comprising a tread band.

[0056] Preferably, the tread band comprises a central annular portion extending astride of an equatorial plane.

[0057] Preferably, the tyre comprises two lateral annular portions arranged on opposite sides with respect to the central annular portion.

[0058] Preferably, the central annular portion comprises a plurality of circumferential grooves. Preferably, each circumferential groove comprises an intermediate portion.

[0059] Preferably, each circumferential groove comprises two end portions arranged on opposite sides with respect to said intermediate portion along a circumferential direction.

[0060] Preferably, said intermediate portion has a width less than the maximum width of each of the two end portions.

[0061] The Applicant believes that a tyre for Sport Touring motorcycle of the type described above is able to combine performances on the wet surface in line with those expected by the customers with improved performances on the dry surface in terms of driveability, grip and stability with respect to those offered by the reference tyres.

[0062] According to the Applicant, the improved performances on the dry surface are achieved thanks to the closure of the circumferential grooves at their portions having a reduced width caused by the high contact forces provided in the footprint area when the tyre is travelling on the dry surface.

[0063] The expected performances on the wet surface are instead obtainable thanks to the fact that in this driving condition the contact forces in the footprint area are lower than those necessary to close the aforementioned portions having a reduced width. The latter therefore remain open, to the benefit of water drainage.

[0064] By carrying out road tests, the Applicant even found a surprising improvement in the grip on the wet surface.

[0065] Without being bound by any interpretative theory, the Applicant considers that this unexpected improvement might be the consequence of the fact that at the portions having a reduced width the water entering the circumferential grooves undergoes an acceleration that results in a more effective and immediate drainage of the water.

[0066] The present invention may have at least one of the preferred features described hereinbelow.

[0067] Preferably, the width of the central annular portion is equal to or less than that of each of the two lateral annular portions.

[0068] Preferably, the two lateral annular portions have the same width.

[0069] Preferably, the central annular portion has a width such that the ratio between said width and the maximum width of radial section of the tyre is less than 35%, more preferably less than 30%.

[0070] Preferably, the central annular portion has a width such that the ratio between said width and the maximum width of radial section of the tyre is greater than 15%, more preferably greater than 20%.

[0071] In preferred embodiments, the central annular portion has a width such that the ratio between said width and the maximum width of radial section of the tyre is comprised between 15% and 35%, preferably between 20% and 30%, for example equal to 25% or 26%.

[0072] Preferably, each lateral annular portion has a width such that the ratio between said width and the maximum width of radial section of the tyre is greater than 25%, more preferably greater than 30%.

[0073] Preferably, each lateral annular portion has a width such that the ratio between said width and the maximum width of radial section of the tyre is less than 45%, more preferably less than 40%.

[0074] In preferred embodiments, each lateral annular portion has a width such that the ratio between said width and the maximum width of radial section of the tyre is comprised between 25% and 45%, preferably between 30% and 40%, for example equal to 35% or 36%.

[0075] Preferably, the ratio between the width of the intermediate portion and the maximum width of each of the two end portions of each circumferential groove is greater than 0.4, more preferably greater than 0.45, even more preferably greater than 0.5.

[0076] Preferably, the ratio between the width of the intermediate portion and the maximum width of each of the two end portions of each circumferential groove is less than 0.8, more preferably less than 0.75, even more preferably less than 0.7.

[0077] In preferred embodiments, the ratio between the width of the intermediate portion and the maximum width of each of the two end portions of each circumferential groove is comprised between 0.4 and 0.8, preferably between 0.45 and 0.75, more preferably between 0.5 and 0.7.

[0078] Preferably, the ratio between the length of the intermediate portion and the length of each of the two end portions of each circumferential groove is greater than 0.8, more preferably greater than 0.9.

[0079] Preferably, the ratio between the length of the intermediate portion and the length of each of the two end portions of each circumferential groove is less than 1.2, more preferably less than 1.1, even more preferably less than 1.

[0080] In preferred embodiments, the ratio between the length of the intermediate portion and the length of each of the two end portions of each circumferential groove is comprised between 0.8 and 1.2, preferably between 0.9 and 1.1, more preferably between 0.9 and 1.

[0081] It is the Applicant's opinion that the provision in the circumferential grooves of intermediate portions having a reduced width and of end portions having a width and a length as described above allows maximizing the performances of the tyre on the dry surface as well as on the wet surface. In fact, the Applicant believes that in this way the two opposite faces of the circumferential groove are arranged at a mutual distance such as to be in contact with each other at the intermediate portion having a reduced width while travelling on the dry surface, to the benefit of the grip on the road surface, whereas they remain spaced apart from each other while travelling on the wet surface, thus leaving the circumferential groove fully open, to the benefit of water drainage. In addition, the two end portions of the groove are sufficiently wide to allow maintaining an optimal compromise between the desired behaviour on the dry surface and the expected behaviour on the wet surface.

[0082] Preferably, at least the end portion which during rolling of the tyre enters in the footprint area before the intermediate portion has a progressively decreasing width moving from a free end of said end portion towards the intermediate portion.

[0083] Preferably, each circumferential groove is arranged alongside the equatorial plane.

[0084] Preferably, each circumferential groove comprises an axially inner face that is concave with respect to the equatorial plane.

[0085] Preferably, said axially inner face has a substantially curvilinear extension.

[0086] Preferably, said axially inner face extends along an arc of circumference having a predetermined first radius of curvature and center of curvature.

[0087] Preferably, said center of curvature is arranged on the opposite side with respect to the equatorial plane.

[0088] Preferably, said first radius of curvature is greater than 100 mm, more preferably greater than 120 mm, even more preferably greater than 140 mm.

[0089] Preferably, said first radius of curvature is less than 200 mm, more preferably less than 180 mm, even more preferably less than 160 mm.

[0090] In preferred embodiments, said first radius of curvature is comprised between 100 mm and 200 mm, preferably between 120 mm and 180 mm, more preferably between 140 mm and 160 mm.

[0091] Preferably, said plurality of circumferential grooves comprises a first series of circumferential grooves arranged on one side with respect to the equatorial plane.

[0092] Preferably, said plurality of circumferential grooves comprises a second series of circumferential grooves arranged on the other side with respect to the equatorial plane.

[0093] Preferably, the circumferential grooves of the first series of circumferential grooves are offset along said circumferential direction with respect to the circumferential grooves of the second series of circumferential grooves.

[0094] Preferably, the circumferential grooves of the second series of circumferential grooves have a shape that is specular to that of the circumferential grooves of the first series of circumferential grooves.

[0095] Preferably, the offset in the circumferential direction of the aforementioned circumferential grooves is such that the intermediate portion of each circumferential groove of the first series of circumferential grooves is axially adjacent to an end portion of a respective circumferential groove of the second series of circumferential grooves.

[0096] Preferably, the offset in the circumferential direction of the aforementioned circumferential grooves is such that the intermediate portion of each circumferential groove of the second series of circumferential grooves is axially adjacent to an end portion of a respective circumferential groove of the first series of circumferential grooves.

[0097] The Applicant has found that an offset as described hereinabove, ensuring an overlap in axial direction of the circumferential grooves of the first series of circumferential grooves with those of the second series of circumferential grooves such as to make adjacent in axial direction portions of the circumferential groove having a reduced width and end portions of another circumferential groove, allows to achieve an advantageous regularity of behaviour of the tyre during its rolling. This is not only beneficial to the behaviour on dry surface and wet surface, but also with respect to noise, vibration and wear.

[0098] Preferably, the tread band further comprises a plurality of first transversal grooves. These grooves contribute to defining the desired void to solid ratio in the tread band.

[0099] Preferably, said first transversal grooves have an axially inner portion arranged in said central annular portion. Therefore they cooperate with the circumferential grooves to drain water from the footprint area when the tyre is travelling on the wet surface, both in a straight line and when bending.

[0100] Preferably, said first transversal grooves have an axially outer portion arranged in one of said lateral annular portions, so as to direct the water outside the footprint area when the tyre is travelling on the wet surface.

[0101] Preferably, said axially inner portion has a width less than the maximum width of said axially outer portion. This axially inner portion therefore behaves as discussed above with reference to the portions of circumferential grooves having a reduced width, contributing to achieving the desired improvement in performance on the dry surface and the expected behaviour on the wet surface.

[0102] Preferably, the ratio between the width of the axially inner portion and the maximum width of the axially outer portion of each first transversal groove is greater than 0.4, more preferably greater than 0.45.

[0103] Preferably, the ratio between the width of the axially inner portion and the maximum width of the axially outer portion of each first transversal groove is less than 0.7, more preferably less than 0.65.

[0104] In preferred embodiments, the ratio between the width of the axially inner portion and the maximum width of the axially outer portion of each first transversal groove is comprised between 0.4 and 0.7, preferably between 0.45 and 0.65.

[0105] Preferably, the axially outer portion has a width that progressively decreases moving from said axially inner portion towards a free end of said axially outer portion.

[0106] Preferably, the axially inner portion of each first transversal groove is shorter than the axially outer portion of the same first transversal groove.

[0107] Preferably, the ratio between the length of the axially inner portion of each first transversal groove and the length of the axially outer portion of the same first transversal groove is greater than 0.3.

[0108] Preferably, the ratio between the length of the axially inner portion of each first transversal groove and the length of the axially outer portion of the same first transversal groove is less than 0.5.

[0109] In preferred embodiments, the ratio between the length of the axially inner portion of each first transversal groove and the length of the axially outer portion of the same first transversal groove is comprised between 0.3 and 0.5.

[0110] The Applicant believes that the values mentioned above in relation to the width and length of the axially inner portions with respect to those of the axially outer portions of the transversal grooves allow to optimize the behaviour on the dry surface without penalizing the one on the wet surface.

[0111] Preferably, each first transversal groove is arranged alongside the equatorial plane.

[0112] Preferably, each first transversal groove comprises an axially inner face that is convex with respect to the equatorial plane.

[0113] Preferably, said axially inner face extends along an arc of circumference having a predetermined second radius of curvature and center of curvature.

[0114] Preferably, said center of curvature is arranged on the same side with respect to the equatorial plane.

[0115] Preferably, said second radius of curvature is smaller than said first radius of curvature.

[0116] Preferably, the ratio between the second radius of curvature and the first radius of curvature is greater than 0.2, more preferably greater than 0.3, even more preferably greater than 0.4.

[0117] Preferably, the ratio between the second radius of curvature and the first radius of curvature is less than 0.8, more preferably less than 0.7, even more preferably less than 0.6.

[0118] In preferred embodiments, the ratio between the second radius of curvature and the first radius of curvature is comprised between 0.2 and 0.8, preferably between 0.3 and 0.7, more preferably between 0.4 and 0.6.

[0119] Preferably, the axially inner portion of each first transversal groove is circumferentially arranged between two circumferentially consecutive circumferential grooves of the same series of circumferential grooves.

[0120] Preferably, said plurality of first transversal grooves comprises a first series of first transversal grooves arranged on one side with respect to the equatorial plane.

[0121] Preferably, said plurality of first transversal grooves comprises a second series of first transversal grooves arranged on the other side with respect to the equatorial plane.

[0122] Preferably, the transversal grooves of the first series of first transversal grooves are offset along said circumferential direction with respect to the transversal grooves of the second series of first transversal grooves.

[0123] Preferably, the axially inner portion of the transversal grooves of the first series of first transversal grooves is circumferentially offset with respect to the axially inner portion of the transversal grooves of the second series of first transversal grooves.

[0124] Preferably, the axially inner portion of each transversal groove of the first series of first transversal grooves is axially adjacent to the axially outer portion of a respective transversal groove of the second series of first transversal grooves. The offset of the first transversal grooves is functional to the behaviour of the tyre on dry and wet conditions. Therefore, the considerations made above with reference to the offset of the circumferential grooves apply.

[0125] Preferably, the tread band comprises a plurality of second transversal grooves.

[0126] Preferably, said second transversal grooves are entirely arranged in said lateral annular portions. The second transversal grooves enter in the footprint area only when the tyre is bending and contribute to the drainage of water from the footprint area under such driving conditions. They also contribute to defining the desired void to solid ratio in the tread band.

[0127] Preferably, said plurality of second transversal grooves comprises a first series of second transversal grooves arranged on one side with respect to the equatorial plane.

[0128] Preferably, said plurality of second transversal grooves comprises a second series of second transversal grooves arranged on the other side with respect to the equatorial plane.

[0129] Preferably, the transversal grooves of the first series of second transversal grooves are offset along said circumferential direction with respect to the transversal grooves of the second series of second transversal grooves.

[0130] Preferably, at least two of said second transversal grooves are arranged between two circumferentially consecutive first transversal grooves of the same series of first transversal grooves.

[0131] More preferably, the number of the second transversal grooves that are arranged between two circumferentially consecutive first transversal grooves of the same series of first transversal grooves is greater than 2.

[0132] More preferably, the number of the second transversal grooves that are arranged between two circumferentially consecutive first transversal grooves of the same series of first transversal grooves is less than 4.

[0133] In preferred embodiments, the number of the second transversal grooves that are arranged between two circumferentially consecutive first transversal grooves of the same series of first transversal grooves is comprised between 2 and 4.

[0134] DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0135] Further characteristics and advantages of the present invention will be more evident from the following description of some preferred embodiments thereof made with reference to the appended drawings. In such drawings:

[0136] - figure 1 is a schematic view of a radial section of a rear tyre in accordance with the present invention, where for simplicity of illustration the tread band is shown without grooves;

[0137] - figure 2 is a front view of a rear tyre in accordance with the present invention;

[0138] - figure 3 is an enlargement of a portion of the tyre of figure 2;

[0139] - figure 4 is an enlargement of a central annular portion of the tread band of the tyre of figure 2;

[0140] - figure 5 is a further enlargement of a portion of the tyre of figure 2.

[0141] With reference to figure 1, a motorcycle tyre in accordance with the present invention is labelled with numeral reference 1.

[0142] What is described hereinbelow with reference to figure 1 applies identically both in the case of a rear tyre and in the case of a front tyre.

[0143] The tyre 1 is a tyre for motorcycles of the "Sport Touring" segment with large piston displacement as discussed above.

[0144] The tyre 1 is intended to be mounted on wheel rims having fitting diameters comprised between about 16 inches and about 21 inches. In the tyre 1, an equatorial plane X-X and a rotation axis (not shown) are defined. A circumferential direction arranged according to the direction of rotation R. of the tyre 1 (figures 2-5) and therefore parallel to the equatorial plane X-X and an axial direction perpendicular to the equatorial plane X-X and / or parallel to the rotation axis are also defined.

[0145] The tyre 1 comprises a carcass structure 2 formed by at least one carcass ply 3 consisting of a sheet of elastomeric material incorporating a plurality of reinforcing cords (not shown) in fibrous textile material.

[0146] In the tyre of figure 1, the carcass structure 2 is of the radial type, i.e. the reinforcing cords of said at least one carcass ply 3 are arranged, in a crown portion of the tyre 1, substantially parallel to each other according to an angle comprised between 70° and 110°, more preferably between 80° and 100°, for example equal to 90°, with respect to the circumferential direction.

[0147] In an embodiment not shown, the carcass structure comprises at least two carcass plies radially superimposed on each other. In this case, the reinforcing cords are essentially parallel to each other in each carcass ply and are oriented according to inclined directions with respect to the equatorial plane of the tyre in each carcass ply and according to opposite directions with respect to the reinforcing cords of the radially adjacent carcass ply 3 (cross-ply carcass).

[0148] The carcass structure 2 is typically covered, on the inner walls thereof, by a sealing layer 100, so-called "liner", essentially consisting of a layer of air-impermeable elastomeric material, adapted to guarantee the hermetic seal of the tyre 1 itself once inflated.

[0149] The (or each) carcass ply 3 is shaped according to a substantially toroidal configuration and has its axially opposite lateral edges 3a turned up on respective annular reinforcing structures 4 intended to retain the tyre 1 on a corresponding mounting rim (not shown). The annular reinforcing structures 4 are typically referred to as "bead cores". On the outer perimeter edge of the bead cores 4 a tapered elastomeric filler 5 is applied which occupies the space defined between the respective carcass ply 3 and the corresponding turned up lateral edge 3a of the carcass ply 3.

[0150] The zone of the tyre 1 comprising the bead core 4 and the elastomeric filler 5 forms the so-called bead 9, which is intended for anchoring the tyre 1 on the rim.

[0151] Preferably, a carcass reinforcing structure may be provided in a radially outer position with respect to the carcass structure (whether radial or cross-ply). Said carcass reinforcing structure comprises a crown ply arranged in a radially outer position with respect to the radially outermost carcass ply and at least at a crown portion of the latter. The crown ply comprises reinforcing elements arranged parallel to each other. The crown ply is arranged on the radially outermost carcass ply so that the reinforcing elements of the crown ply have, with respect to the equatorial plane, an angle opposite to that of the reinforcing cords of the radially outermost carcass ply. Optionally, the carcass reinforcing structure also comprises two plies arranged on opposite sides with respect to the crown ply and not associated with the respective beads.

[0152] In one embodiment thereof, the (or each) carcass ply 3 is made by juxtaposing a plurality of strips of elastomeric material reinforced by the aforementioned reinforcing cords.

[0153] A belt structure 6 is circumferentially applied on the carcass structure 2, in a radially outer position with respect to the latter. The belt structure 6 comprises at least one belt layer 6a typically formed by textile or metallic reinforcing cords embedded in a layer of elastomeric material.

[0154] Preferably, the belt structure 6 is of the zero-degree type, i.e. the belt layer 6a is made by reinforcing cords arranged substantially parallel and side by side so as to form a plurality of coils. These coils are substantially oriented according to the circumferential direction (typically with an angle comprised between 0° and 5°), this direction being usually defined as "at zero degrees" with reference to its lying with respect to the circumferential direction of the tyre 1.

[0155] The belt layer 6a, typically defined as at "zero degrees", may comprise axially juxtaposed windings of a single reinforcing cord or of a rubberized strip-like element comprising axially flanked reinforcing cords.

[0156] The reinforcing cords of the zero-degree belt layer 6a are typically metallic, made by wires of steel with a high carbon content, i.e. wires of steel with a carbon content of at least 0.6% - 0.7%. Preferably, said metal reinforcing cords have a high elongation (HE).

[0157] Optionally, in some tyres, as the one shown in figure 1, an adhesion layer 7 of elastomeric material is arranged between the belt structure 6 and the carcass structure 2 in order to improve the adhesion between the aforementioned structures.

[0158] In a different embodiment, the belt structure comprises two or more radially superimposed belt layers, each layer consisting of elastomeric material incorporating reinforcing cords that are arranged parallel to each other. The belt layers are arranged in such a way that the reinforcing cords of a first belt layer are oriented obliquely with respect to the equatorial plane of the tyre, while the reinforcing cords of the radially adjacent belt layer also have an oblique but crossed orientation with respect to the reinforcing cords of the first layer, so as to form the so-called "cross belt". The same applies to possible additional belt layers, if any. The cross belt typically comprises textile reinforcing cords.

[0159] A tread band 8 is circumferentially superimposed on the belt structure 6, in a radially outer position with respect to the latter.

[0160] Upon a moulding operation carried out in conjunction with a vulcanisation step of the tyre 1, a plurality of grooves oriented as discussed in the remainder of the present description are obtained on the tread band 8, so as to define a particular tread pattern. As already mentioned, for simplicity of illustration in figure 1 the aforementioned grooves are not depicted.

[0161] The tread band 8 (as well as further tyre components not described / illustrated as they are conventional) is made of an elastomeric material.

[0162] The tyre 1 of figure 1 further comprises a pair of sidewalls 10 applied laterally on opposite sides to the carcass structure 2 and also made of elastomeric material.

[0163] With reference to figure 1, the tyre 1 has a section height H measured, on the equatorial plane X-X, between the top of the tread band 8 and the fitting diameter identified by a reference line r passing through the beads 9 of the tyre 1.

[0164] The tyre 1 also has a radial section maximum width C defined, with reference to figure 1, by the distance between the laterally opposite ends E of the tread band 8, and an arrow f, defined by the distance of the top of the tread band 8 from a line L passing through said laterally opposite ends E, measured on the equatorial plane X-X of the tyre 1. The laterally opposite ends E of the tread band 8 may be formed with an edge.

[0165] The tyre 1 preferably has a radial section maximum width C comprised between 120 mm and 200 mm, more preferably equal to 120 mm in the case of a front tyre and 180 mm in the case of a rear tyre.

[0166] The tyre 1 has a curvature ratio f / C, defined by the ratio between the arrow f and the aforementioned radial section maximum width C, and a ratio of arrow over total height (f / H) defined by the ratio between the arrow f and the section height H.

[0167] In the case where the tyre l is a rear tyre, the arrow f is preferably comprised between about 45 mm and about 65 mm, the curvature ratio f / C is preferably comprised between about 0.45 and about 0.65, and the ratio of arrow over total height f / H is preferably comprised between about 0.4 to about 0.6.

[0168] In the case where the tyre 1 is a front tyre, the arrow f is preferably comprised between about 40 mm and about 60 mm, the curvature ratio f / C is preferably comprised between about 0.3 and about 0.6, and the ratio of arrow over total height f / H is preferably comprised between about 0.4 and about 0.7.

[0169] With reference to figures 2-5, the tread design of the tread band 8 of a preferred embodiment of a tyre 1 made in accordance with the present invention is described hereinbelow. In these figures, R. indicates the rolling direction of the tyre 1, which in the specific case illustrated herein is a rear tyre. However, what is described hereinbelow finds analogous application in the case of a front tyre.

[0170] The tread band 8 has a void to solid ratio comprised between 7% and 14%, preferably between 8% and 13%, more preferably between 9% and 12%, for example equal to 10% in the case of a rear tyre whose size is 180 / 55 / R.17 and equal to 11.3% in the case of a front tyre whose size is 120 / 70 / R17.

[0171] As shown in figures 2 and 3, the tread band 8 comprises a central annular portion A extending astride of the equatorial plane and two lateral annular portions S arranged on opposite sides with respect to the central annular portion A.

[0172] The lateral annular portions S have the same width.

[0173] The central annular portion A has a width equal to or less than that of the lateral annular portions S.

[0174] The width of the central annular portion A is such that the ratio between this width and the maximum width of radial section C is comprised between 5% and 15%, for example equal to 10%.

[0175] The width of each of the lateral annular portions S is such that the ratio between this width and the maximum width of radial section C is comprised between 42.5% and 47.5%, for example equal to 45%. As shown in figure 3, an axially inner annular portion A* of the central annular portion A is free of grooves. The axially inner portion A* is arranged astride of the equatorial plane X-X.

[0176] The tread band 8 comprises a plurality of circumferential grooves 20, 60 formed in the central annular portion A and arranged on opposite sides with respect to the equatorial plane X-X in an axially outermost position with respect to the axially inner annular portion A*.

[0177] In particular, the central annular portion A comprises a first series of circumferentially consecutive circumferential grooves 20 arranged on one side with respect to the equatorial plane X-X and a second series of circumferentially consecutive circumferential grooves 60 arranged on the other side with respect to the equatorial plane X-X.

[0178] The circumferential grooves 60 have a shape that is specular to that of the circumferential grooves 20 and dimensions identical to those of the latter.

[0179] The circumferential grooves 20 are circumferentially offset with respect to the circumferential grooves 60.

[0180] The circumferential grooves 20 and 60 will be described in more detail below in this description with reference to figure 4.

[0181] With reference to figures 2 and 3, the tread band 8 further comprises a plurality of first transversal grooves 30, 70 arranged on opposite sides with respect to the equatorial plane X-X in an axially outermost position with respect to the axially inner annular portion A*.

[0182] In particular, a first series of circumferentially consecutive transversal grooves 30 is arranged on one side with respect to the equatorial plane X-X and a second series of circumferentially consecutive transversal grooves 70 is arranged on the other side with respect to the equatorial plane X-X.

[0183] The transversal grooves 70 have a shape that is specular to that of the transversal grooves 30 and dimensions identical to those of the latter.

[0184] Each transversal groove 30 is circumferentially arranged between two respective circumferentially consecutive circumferential grooves 20. Similarly, each transversal groove 70 is circumferentially arranged between two respective circumferentially consecutive circumferential grooves 60.

[0185] The transversal grooves 30 are circumferentially offset with respect to the transversal grooves 70.

[0186] The transversal grooves 30 and 70 will be described in more detail below in this description with reference to figure 5.

[0187] With reference to figures 2 and 3, the tread band 8 also comprises a plurality of second transversal grooves 41, 42, 43; 81, 82, 83 arranged on opposite sides with respect to the equatorial plane X-X in an axially outermost position with respect to the central annular portion A.

[0188] In particular, a first series of three circumferentially consecutive transversal grooves 41, 42, 43 is arranged on one side with respect to the central annular portion A and a second series of three circumferentially consecutive transversal grooves 81, 82, 83 is arranged on the other side with respect to the central annular portion A.

[0189] The three transversal grooves 81, 82, 83 have a shape that is specular to that of the three transversal grooves 41, 42, 43, respectively, and dimensions identical to those of the latter.

[0190] The three transversal grooves 41, 42, 43 are circumferentially arranged between two respective circumferentially consecutive transversal grooves 30. Similarly, the three transversal grooves 81, 82, 83 are circumferentially arranged between two respective circumferentially consecutive transversal grooves 70.

[0191] The three transversal grooves 41, 42, 43 are circumferentially offset with respect to the three transversal grooves 81, 82, 83.

[0192] The transversal grooves 41, 42, 43 and 81, 82, 83 will be described in more detail below in this description with reference to figure 3.

[0193] Details regarding the circumferential grooves 20, 60 are provided hereinbelow.

[0194] As shown in figure 4, each circumferential groove 20 comprises an intermediate portion 21 circumferentially arranged between two opposite end portions 22, 23. Similarly, each circumferential groove 60 comprises an intermediate portion 61 circumferentially arranged between two opposite end portions 62, 63.

[0195] During rolling of the tyre 1, the end portions 22, 62 enter in the footprint area before the intermediate portions 21, 61 and the end portions 23, 63.

[0196] The end portion 22, 62 comprises a free end 22a, 62a arranged at a distance DI from the equatorial plane X-X and an opposite end connected to the intermediate portion 21, 61 and located at a distance D3 from the equatorial plane X-X. Similarly, the end portion 23, 63 comprises a free end 23a, 62a arranged at a distance D2 from the equatorial plane X-X and an opposite end connected to the intermediate portion 21, 61 and located at a distance D3 from the equatorial plane X- X.

[0197] Preferably, the ratio between the distances DI and D2 is comprised between 0.1 and 3.

[0198] Preferably, the ratio between the distances DI and D3 is comprised between 0.2 and 1.

[0199] In preferred embodiments, the distance DI is comprised between 5 mm and 15 mm, the distance D2 is comprised between 10 mm and 20 mm, and the distance D3 is comprised between 25 mm and 35 mm.

[0200] In some embodiments, the distance D2 is substantially equal to the distance DI.

[0201] The intermediate portions 21, 61 have a width Wla smaller than both the maximum width Wlb of the respective end portions 22, 62 and the maximum width Wlc of the respective end portions 23, 63. In particular, the ratios between the width Wla and the maximum width Wlb and between the width Wla and the maximum width Wlc are comprised between 0.4 and 0.8, preferably between 0.45 and 0.75, preferably between 0.5 and 0.7.

[0202] As shown in figure 4, the end portions 22, 62 have a width Wlb that progressively decreases moving from the intermediate portion 21, 61 towards the free end 22a, 62a.

[0203] The intermediate portions 21, 61 have a length Lla substantially equal to both the length Lib of the respective end portions 22, 62 and to the length Lie of the respective end portions 22, 62. In particular, the ratios between the length Lla and the length Lib and between the length Lla and the length Lie are comprised between 0.8 and 1.2, preferably between 0.9 and 1.1, more preferably between 0.9 and 1.

[0204] Each circumferential groove 20, 60 is arranged alongside the equatorial plane X-X and has an axially inner face 20a, 60a that is concave with respect to the equatorial plane X-X and has a substantially curvilinear extension. In particular, each axially inner face 20a, 60a extends along a respective arc of circumference having a radius of curvature R.1 and center of curvature Cl arranged on the opposite side with respect to the equatorial plane X-X.

[0205] The radius of curvature R.1 is preferably comprised between 100 mm and 200 mm, more preferably between 120 mm and 180 mm, even more preferably between 140 mm and 160 mm.

[0206] As already mentioned, the circumferential grooves 20 are circumferentially offset with respect to the circumferential grooves 60. In other words, each circumferential groove 20 is only partially superimposed in the axial direction on a respective circumferential groove 60. In particular, the offset in the circumferential direction of the circumferential grooves 20 and 60 is such that:

[0207] - the intermediate portion 21 of each circumferential groove 20 is axially adjacent to the end portion 61 of a respective circumferential groove 60;

[0208] - the intermediate portion 61 of each circumferential groove 60 is axially adjacent to the end portion 22 of a respective circumferential groove 20;

[0209] - the end portion 23 of each circumferential groove 20 is arranged at a respective axial portion of the tread band 8 in which no circumferential groove portions 60 are provided;

[0210] - the end portion 62 of each circumferential groove 60 is arranged at a respective axial portion of the tread band 8 in which no circumferential groove portions 20 are provided.

[0211] Details regarding the transversal grooves 30, 70 are provided hereinbelow.

[0212] As shown in figure 5, each transversal groove 30, 70 comprises a respective axially inner portion 31, 71 arranged in the central annular portion A, alongside the equatorial plane X-X, and a respective axially outer portion 32, 72 arranged in the respective lateral annular portion S.

[0213] The axially inner portion 31 of each transversal groove 30 is circumferentially arranged between two respective circumferentially consecutive circumferential grooves 20. Similarly, the axially inner portion 71 of each transversal groove 70 is circumferentially arranged between two respective circumferentially consecutive circumferential grooves 60.

[0214] The axially inner portion 31, 71 of each transversal groove 30, 70 has a width W2a less than the maximum width W2b of the axially outer portion 32, 72 of the transversal groove 30, 70. In particular, the ratio between the width W2a and the maximum width W2b is comprised between 0.4 and 0.7, preferably between 0.45 and 0.65.

[0215] The width W2a is substantially constant along the entire axially inner portion 31, 71, while the width W2b progressively decreases moving from the axially inner portion 31, 71 towards the free end 32a, 72a of the axially outer portion 32, 72.

[0216] The axially inner portion 31, 71 has a length L2a less than the length L2b of the axially outer portion 32, 72. In particular, the ratio between the length L2a and the length L2b is comprised between 0.3 and 0.5.

[0217] Each transversal groove 30, 70 has an axially inner face 30a, 70a that is convex with respect to the equatorial plane X-X and has a substantially curvilinear extension. In particular, each axially inner face 30a, 70a extends along a respective arc of circumference having a radius of curvature R.2 and center of curvature C2 arranged on the same side with respect to the equatorial plane X-X.

[0218] The ratio between the radius of curvature R.2 and the radius of curvature R1 is preferably comprised between 1.2 and 0.4, more preferably between 1 and 0.6, even more preferably between 0.9 and 0.7.

[0219] In the example shown herein, the radius of curvature R2 is less than the radius of curvature Rl.

[0220] As already mentioned, the transversal grooves 30 are circumferentially offset with respect to the transversal grooves 70. In other words, each transversal groove 30 is only partially superimposed in the axial direction on a respective transversal groove 70.

[0221] In particular, the offset in the circumferential direction of the transversal grooves 30 and 70 is such that:

[0222] - the axially inner portion 31 of each transversal groove 30 is circumferentially offset with respect to the axially inner portion 71 of a respective transversal groove 71 and vice versa;

[0223] - the axially inner portion 31 of each transversal groove 30 is axially adjacent to a part of the axially outer portion 72 of the aforementioned transversal groove 70;

[0224] - a part of the axially outer portion 32 of each transversal groove 30 is axially adjacent to an end portion 61 of a respective circumferential groove 60 and partially superimposed in the axial direction on the remaining part of the axially outer portion 72 of a respective transversal groove 70;

[0225] - the remaining part of the axially outer portion 32 of each transversal groove 30 is axially adjacent to the end portion 22 of a respective circumferential groove 20 and partially superimposed in the axial direction on the intermediate portion 61 of a respective circumferential groove 60;

[0226] - the axially inner portion 72 of each transversal groove 70 is not axially adjacent to a respective transversal groove 30.

[0227] Details regarding the transversal grooves 41, 42, 43 and 81, 82, 83 are provided hereinbelow.

[0228] Although in the example shown in figures 2, 3 and 5 groups of three transversal grooves 41, 42, 43 are provided that are circumferentially arranged between two circumferentially consecutive transversal grooves 30 and groups of three transversal grooves 81, 82, 83 are provided that are circumferentially arranged between two circumferentially consecutive transversal grooves 70, the number of the transversal grooves belonging to each of the aforementioned groups may also be two or four.

[0229] With reference to figure 3, the transversal grooves 41, 42, 43 and 81, 82, 83 are entirely arranged in the lateral annular portions S of the tread band 8.

[0230] The circumferential extension of the transversal grooves 41, 42, 43 and 81, 82, 83 is less than that of the circumferential grooves 20, 60 and of the transversal grooves 30, 70. As already mentioned, the transversal grooves 41, 42, 43 are circumferentially offset with respect to the transversal grooves 81, 82, 83.

[0231] In particular, the offset in the circumferential direction of the transversal grooves 41, 42, 43 and 81, 82, 83 is such that:

[0232] - each transversal groove 41 is axially adjacent to a respective transversal groove 30;

[0233] - each transversal groove 81 is axially adjacent to a respective transversal groove 70;

[0234] - each transversal groove 43 is axially adjacent to a respective circumferential groove 20;

[0235] - each transversal groove 83 is axially adjacent to a respective circumferential groove 60;

[0236] - each transversal groove 42 is circumferentially arranged between a respective transversal groove 41 and a respective transversal groove 43 and has a part partially superimposed in the axial direction on the end portion 53 of a respective circumferential groove 20 and the remaining part is superimposed in the axial direction on the axially inner portion 71 of a respective transversal groove 70;

[0237] - each transversal groove 82 is circumferentially arranged between a respective transversal groove 81 and a respective transversal groove 82 and has a part superimposed in the axial direction on the end portion 23 of a respective circumferential groove 60 and the remaining part is superimposed in the axial direction on the end portion 23 of a respective circumferential groove 20.

[0238] COMPARATIVE TESTS

[0239] The Applicant has made a sample of a rear tyre 1 in accordance with an embodiment of the present invention and having in particular the tread design shown in figures 2-5. This tyre hereinbelow is indicated with INV. The tyre INV had a structure and dimensions identical to those of a rear tyre for Applicant's Sport Touring motorcycles (hereinafter referred to as Ref) currently sold on the market and also appreciated by the customers for its excellent behaviour both on the dry surface and on the wet surface.

[0240] The tests were carried out by mounting the tyres INV and Ref (inflated with the same inflation pressure) on the rear wheel of a motorcycle Kawasaki Versys 1000, with an identical tyre mounted on the front wheel and under substantially identical environmental conditions. The tests were performed both under ambient conditions defined as "cold", i.e. with asphalt temperature and ambient temperature comprised between 10 C and 15 C, and under ambient conditions defined as "hot", i.e. with asphalt temperature comprised between 40 C and 50 C and ambient temperature comprised between 27 C and 37 C.

[0241] The behaviour of the two tyres INV and Ref was evaluated both on the dry surface and on the wet surface, asking the rider for his opinion. In particular, the items listed in Table 1 reported hereinbelow were evaluated, where the opinion expressed by the rider is also reported.

[0242] The tests were performed by driving on routes with straight stretches and curves.

[0243] In Table 1, "=" indicates the positive opinion obtained through the tyre Ref and "+" indicates an improvement with respect to the tyre Ref, "+ + " indicates a significant improvement with respect to the tyre Ref. Table 1 shows that the tyre INV offered performance substantially identical to that of the already excellent tyre Ref with reference to driveability on the wet surface and water drainage, with a surprising improvement in the grip on the wet surface.

[0244] The behaviour of the tyre INV was judged to be better also with reference to stability and much better with reference to driveability and grip on the dry surface, confirming that the Applicant's objective of allowing an even sportier driving, tending towards the one allowed by the motorcycle tyres of the "Supersport" segment, had been achieved.

[0245] Of course, a person skilled in the art can make further modifications and changes to the tyre of the invention described above in order to satisfy specific and contingent application needs, such modifications and changes in any case falling within the scope of protection defined by the following claims.

Claims

CLAIMS1. Motorcycle tyre (1), comprising a tread band (8) having a central annular portion (A) extending astride of an equatorial plane (X- X) of the tyre (1) and two lateral annular portions (S) arranged on opposite sides with respect to the central annular portion (A), wherein the central annular portion (A) comprises a plurality of circumferential grooves (20; 60) each having an intermediate portion (21; 61) and two end portions (22, 23; 62, 63) arranged on opposite sides with respect to said intermediate portion (21; 61) along a circumferential direction, wherein said intermediate portion (21; 61) has a width (Wla) less than the maximum width (Wlb, Wlc) of each of the two end portions (22, 23; 62, 63).

2. Tyre (1) according to claim 1, wherein the ratio between the width (Wla) of the intermediate portion (21; 61) and the maximum width (Wlb, Wlc) of each of the two end portions (22, 23; 62, 63) is comprised between 0.4 and 0.8.

3. Tyre (1) according to claim 1 or 2, wherein the ratio between the length (Lla) of the intermediate portion (21; 61) and the length (Lib, Lie) of each of the two end portions (22, 23; 62, 63) is comprised between 0.8 and 1.2.

4. Tyre (1) according to any one of the previous claims, wherein each circumferential groove (20; 60) is arranged alongside the equatorial plane (X-X) and comprises an axially inner face (20a; 60a) that is concave with respect to the equatorial plane (X-X) and that extends along an arc of circumference having a predetermined first radius of curvature (R.1) and a center of curvature (Cl) arranged on the opposite side with respect to the equatorial plane (X-X).

5. Tyre (1) according to any one of the previous claims, wherein said plurality of circumferential grooves (20; 60) comprises a first series of circumferential grooves (20) arranged on one side with respect to theequatorial plane (X-X) and a second series of circumferential grooves (60) arranged on the other side with respect to the equatorial plane (X- X), wherein the circumferential grooves (20) of the first series of circumferential grooves (20) are offset along said circumferential direction with respect to the circumferential grooves (60) of the second series of circumferential grooves (60) so that the intermediate portion (21) of each circumferential groove (20) of the first series of circumferential grooves (20) is axially adjacent to an end portion (63) of a respective circumferential groove (60) of the second series of circumferential grooves (60) and the intermediate portion (61) of each circumferential groove (60) of the second series of circumferential grooves (60) is axially adjacent to an end portion (22) of a respective circumferential groove (20) of the first series of circumferential grooves (20).

6. Tyre (1) according to any one of the previous claims, wherein the tread band (8) also comprises a plurality of first transversal grooves (30; 70) having an axially inner portion (31; 71) arranged in said central annular portion (A) and an axially outer portion (32; 72) arranged in one of said lateral annular portions (S), wherein said axially inner portion (31; 71) has a width (W2a) less than the maximum width (W2b) of said axially outer portion (32; 72).

7. Tyre (1) according to claim 6, wherein the ratio between the width (W2a) of the axially inner portion (31; 71) and the maximum width (W2b) of the axially outer portion (32; 72) is comprised between 0.4 and 0.7.

8. Tyre (1) according to claim 6 or 7, wherein the axially inner portion (31; 71) of each first transversal groove (30; 70) is shorter than the axially outer portion (32; 72) of the same first transversal groove (30; 70).

9. Tyre (1) according to any one of claims 6 to 8, wherein eachfirst transversal groove (30; 70) is arranged alongside the equatorial plane (X-X) and comprises an axially inner face (30a, 70a) that is convex with respect to the equatorial plane (X-X) and that extends along an arc of circumference having a predetermined second radius of curvature (R.2) and a center of curvature (C2) arranged on the same side with respect to the equatorial plane (X-X).

10. Tyre (1) according to any one of claims 6 to 9 when depending on claim 5, wherein the axially inner portion (31; 71) of each first transversal groove (30; 70) is circumferentially arranged between two circumferentially consecutive circumferential grooves (20; 60) of the same series of circumferential grooves (20; 60).

11. Tyre (1) according to any one of claims 6 to 10, wherein said plurality of first transversal grooves (30; 70) comprises a first series of first transversal grooves (30) arranged on one side with respect to the equatorial plane (X-X) and a second series of first transversal grooves (70) arranged on the other side with respect to the equatorial plane (X- X), wherein the transversal grooves (30) of the first series of first transversal grooves (30) are offset along said circumferential direction with respect to the transversal grooves (70) of the second series of first transversal grooves (70).

12. Tyre (1) according to claim 11, wherein the axially inner portion (31) of the transversal grooves (30) of the first series of first transversal grooves (30) is circumferentially offset with respect to the axially inner portion (71) of the transversal grooves (70) of the second series of first transversal grooves (70).

13. Tyre (1) according to claim 12, wherein the axially inner portion (31) of each transversal groove (30) of the first series of first transversal grooves (30) is axially adjacent to the axially outer portion (72) of a respective transversal groove (70) of the second series of first transversal grooves (70).

14. Tyre (1) according to any one of claims 6 to 13, wherein the tread band (8) comprises a plurality of second transversal grooves (41, 42, 43; 81, 82, 83) entirely arranged in said lateral annular portions (S).

15. Tyre (1) according to claim 14, wherein said plurality of second transversal grooves (41, 42, 43; 81, 82, 83) comprises a first series of second transversal grooves (41, 42, 43) arranged on one side with respect to the equatorial plane (X-X) and a second series of second transversal grooves (81, 82, 83) arranged on the other side with respect to the equatorial plane (X-X), wherein the transversal grooves (41, 42, 43) of the first series of second transversal grooves (41, 42, 43) are offset along said circumferential direction with respect to the transversal grooves (81, 82, 83) of the second series of second transversal grooves (81, 82, 83).

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