Motorcycle tyre

Abstract

The present invention relates to a motorcycle tyre comprising a tread band having a central annular portion (A) extending astride the 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 in opposite sides with respect to the intermediate portion (21; 61) in the circumferential direction. The width (W1a) of the intermediate portion (21; 61) is smaller than the maximum width (W1b, W1c) of each of the two end portions (22, 23; 62, 63).

Description

Technical Field

[0001] This invention relates to a motorcycle tire.

[0002] The tires of the present invention are intended to equip the front and rear wheels of motorcycles in the “sport touring” segment, which are known to be motorcycles with large piston displacement (e.g., 800 cm³ or higher) and / or medium / high power (e.g., 60 / 80 hp or higher) and capable of reaching or exceeding speeds of 180 km / h and withstanding maximum loads of even higher than 200 kg.

[0003] Some examples of "sport touring" motorcycles are: Kawasaki Versys 1000, BMW S1000XR, and Ducati Multistrada V4 Rally. Background Technology

[0004] Motorcycle tires in the "sport touring" segment typically include a tread band with a tread design defined by multiple circumferential and lateral grooves. Examples of such tires are described in WO 2020 / 110075 and WO 2020 / 110080 under the applicant's name.

[0005] The applicant’s WO 2021 / 090152 describes an example of a tire suitable for both motorcycles in the “sport touring” segment and motorcycles in the “super sport” segment. Summary of the Invention

[0006] Throughout this specification and the following claims, when referring to any range of values ​​between the minimum and maximum values, the minimum and maximum values ​​are to be considered included in that range unless otherwise expressly stated.

[0007] Furthermore, even if not explicitly described, all ranges include any combination of the stated minimum and maximum values ​​and include any intermediate ranges.

[0008] Even if not explicitly stated, any numerical value is assumed to be preceded by the term "about" to indicate any value that differs slightly from the stated value, for example, to consider dimensional tolerances common in the field of reference.

[0009] In the following text, the following definitions apply:

[0010] The term "motorcycle tire" is used to refer to tires with a high curvature ratio (typically greater than 0.20) and the ability to achieve a high camber angle when cornering.

[0011] The term "curvature ratio" is used to represent the ratio between the distance between the radially highest point of the tire tread strip and the tire's maximum chord length (also indicated by an "arrow") in the tire's cross-section and the tire's own maximum chord length.

[0012] The terms "maximum chord length" or "maximum width of radial section" are used to indicate the maximum width of the tire profile, that is, the length of the segment with the two outermost points of the tread strip as its endpoints.

[0013] The term "tire footprint area" refers to the portion of the tire that is in contact with the ground or road surface when the tire is mounted on the rim and a predetermined vertical load is applied to the tire.

[0014] The term "contact force" refers to the force transmitted between the tire and the ground, road surface, or asphalt surface in the tire track area during tire rolling.

[0015] The term "equatorial plane" for a tire is used to refer to the plane perpendicular to the tire's axis of rotation and that divides the tire into two symmetrical and equal parts.

[0016] The term "tread pattern" is used to describe the representation of all points of the tread band (including grooves) on a plane perpendicular to the tire's equatorial plane and tangent to the tire's maximum diameter. This representation corresponds to the planar extension of the outermost contour of the tread band.

[0017] Measurements of linear quantities (distance, width, length, axial extension and / or circumferential extension, etc.) and / or angles should be understood with reference to the tread pattern as defined above.

[0018] The term “circumferential extension” for a tire, tread belt or part thereof is used to describe the planar extension of the outermost radial surface of a tire, tread belt or part thereof in a plane tangent to the tire.

[0019] The term "void-to-rubber ratio" is used to describe the ratio between the total surface area of ​​the grooves of a specific annular portion of the tire tread belt or a specific portion of the tire tread pattern (which may be the entire tread belt or the entire tread pattern) and the surface area of ​​that specific annular portion of the tread belt or the specific portion of the tread pattern (which may be the entire tread belt or the entire tread pattern).

[0020] The term "clearance" refers to the total area occupied by grooves or groove portions within the tread band. This total area depends on the number and size of the grooves or groove portions.

[0021] The term "annular portion" of the tread belt is used to refer to the portion of the tread belt that extends circumferentially along the entire tread belt and has a predetermined width.

[0022] The terms “radial” and “axial”, as well as the expressions “radial inside / outer” and “axial inside / outer”, are used with reference to directions substantially parallel to the tire’s equatorial plane and substantially perpendicular to the tire’s equatorial plane, respectively; that is, with reference to directions substantially perpendicular to the tire’s axis of rotation and substantially parallel to the tire’s axis of rotation, respectively.

[0023] The terms "axially inside" and "axially outside" refer to positions closer to or further away from the equatorial plane relative to the reference element, respectively. Therefore, for example, when the axial distance between the first groove portion and the equatorial plane is less than the axial distance between the second groove portion and the equatorial plane, the first groove portion is axially inside relative to the second groove portion. Similarly, when the axial distance between the first groove portion and the equatorial plane is greater than the axial distance between the second groove portion and the equatorial plane, the first groove portion is axially outside relative to the second groove portion.

[0024] The terms “circumferential” and “circumferentially” are used with reference to the circumferential extension direction of the tire (i.e., the direction in which the tire rolls), which corresponds to a direction located on a plane that coincides with or is substantially parallel to the equatorial plane of the tire.

[0025] The term "circumferential groove" is used to describe a groove that extends along a trajectory substantially parallel to the equatorial plane.

[0026] The expression "basically parallel" not only refers to a state of complete parallelism, but also to a state where the angle of deviation from complete parallelism is no greater than 20° (preferably no more than 15°).

[0027] The term "lateral groove" is used to describe a groove that extends along a trajectory inclined at an angle greater than 20° (preferably greater than 25°, and even more preferably greater than 30°) relative to the equatorial plane. In cases where the groove has a generally curved or substantially non-linear extension, the line connecting the two opposite endpoints of the groove is considered as a measure of the inclination angle.

[0028] The term "basic curved extension" is used to describe an extension that has a basic continuity of a curved derivative representing the extension itself. Typically, a basic curved extension has no corner points. However, the definition also includes cases where the extension is obtained through a series of short straight line segments, provided that the angular difference between these short straight line segments is less than 20°.

[0029] In the following text, when the circumferential center points of two grooves or their respective portions are not on the same plane perpendicular to the tire equator, the groove or portion thereof is considered to be "circumferentially offset" relative to the other groove or portion thereof.

[0030] Conversely, when the projections of two trenches or their respective portions onto the equatorial plane are at least partially superimposed on each other, the trenches or portions thereof are considered to be "overlapping in the axial direction" onto the other trench or portion thereof. In this case, the projection of at least a segment of each of the two trenches onto the equatorial plane is the same as the projection of at least a segment of the other trench onto the equatorial plane.

[0031] Regarding the angle of the groove or groove portion relative to the tire's equatorial plane, for each point on the groove or groove portion, this angle should be understood as the angle (in absolute value) formed by performing a rotation, starting from the direction defined by the equatorial plane in the tread pattern and extending to the direction tangent to the groove or groove portion passing through said point. In the case where the tire is intended to be mounted on the rear wheel of a motorcycle, the aforementioned rotation should be understood as a rotation performed by a vector oriented in the opposite direction to the tire's rotation, while in the case where the tire is intended to be mounted on the front wheel of a motorcycle, the aforementioned rotation should be understood as a rotation performed by a vector oriented in the tire's rotation direction.

[0032] If the middle portion of a tire surface or face is further away from the equatorial plane than its end portions, then that surface or face is "concave" relative to the tire's equatorial plane.

[0033] If the middle portion of a tire surface or face is closer to the equatorial plane than at least one of its end portions, then the surface or face is "convex" relative to the tire's equatorial plane.

[0034] The term "width" is used to refer to a dimension measured along a direction orthogonal to the equatorial plane.

[0035] The term “width” for a trench or a portion thereof is used to indicate the dimension measured along a direction orthogonal to the trajectory extending from the trench or a portion thereof.

[0036] The term “length” for a trench or a portion thereof is used to indicate the length of the track along which the trench or a portion extends.

[0037] The term “circumferential extension” for a groove or a portion thereof is used to indicate the projected length of a groove or a portion thereof on a plane parallel to the equatorial plane.

[0038] The applicant has observed that there are sport touring motorcycles on the market with exceptionally high piston displacement and power, such as those with a piston displacement of 1000 cm³. 3 or above, with a power output of 180 horsepower or above.

[0039] The applicant believes that users of this type of motorcycle desire tires that not only achieve the performance typically required for tires used in sport touring motorcycles in terms of mileage, comfort, driving performance, stability, and grip on road surfaces (whether conventional or unconventional, dry or wet, even in harsh weather conditions such as cold), but also performance under particularly high speeds and particularly extreme handling conditions, such as sharp turns during cornering.

[0040] The applicant considered how to improve the performance of a sport touring motorcycle tire with high piston displacement and high power on dry surfaces in terms of driving performance, grip and stability compared to tires in the same segment currently on the market (hereinafter referred to as the "reference tire"), in order to allow for more sporty driving and thus approach the driving performance allowed by motorcycle tires in the "super sport" segment.

[0041] However, the applicant also considered the objective that the performance relative to that provided by the reference tire would not adversely affect the performance on wet surfaces.

[0042] The applicant has observed that, regardless of the market segment a tire belongs to, its performance on dry roads improves as its ability to adhere to the road surface increases, and this ability is greater when the tire is traveling in a straight line and turning, as the number and / or size of the grooves in the tire track area are smaller.

[0043] Therefore, according to the applicant, one way to achieve the desired improvement in the performance of tires used for sport touring motorcycles on dry roads is to reduce the amount of voids in the tire track area.

[0044] However, the applicant has observed that reducing the amount of clearance in the tire track area will lead to a deterioration in performance on wet roads (especially regarding drainage), resulting in a situation that contradicts the original intention of having performance on wet roads at least equal to that of the reference tire on wet roads.

[0045] The applicant has considered how to overcome this impasse and believes that ideally, a tread design would be adopted in which the portion of the tread band that is in the tire track area during tire rolling can “change” its configuration according to the conditions of the road surface on which the tire rolls, in order to switch from a first configuration to a second configuration. In the first configuration, there is an ideal amount of clearance to achieve excellent tire performance on both dry and wet roads, and in the second configuration, there is an ideal amount of clearance to achieve the desired performance improvement on dry roads while maintaining performance on wet roads.

[0046] The applicant has taken into account that the contact force is higher when the tire is traveling on a dry surface than when it is traveling on a wet surface. Therefore, the tread band in the tire track area deforms more when traveling on a dry surface than when traveling on a wet surface.

[0047] The applicant has recognized that the aforementioned "alterable" tread design can be obtained by providing at least some portions of reduced width in at least some of the grooves in the tire track area, said portions of reduced width being configured to close when the contact force is sufficiently large, such as when the tire is traveling on a dry road surface, and remain open when the contact force is further reduced, such as when the tire is traveling on a wet road surface. In fact, the closure of the grooves at the aforementioned portions of reduced width means a temporary reduction in the amount of clearance in the tire track area; this occurs when the tire is traveling on a dry road surface and is beneficial for grip. Subsequently, the grooves at the aforementioned portions of reduced width reopen, causing the amount of clearance to return to its initial value; this occurs when the tire is traveling on a wet road surface and is beneficial for water drainage.

[0048] The applicant has considered that, in order to avoid the undesirable phenomenon of excessive and / or irregular wear of the tread band, it is advantageous for at least some of the grooves in the central annular portion of the tread band to be oriented in a substantially circumferential direction to avoid having groove edges that are laterally oriented relative to the forces acting on the tire during acceleration and braking, at least at these grooves.

[0049] The applicant desires to approximate the dry-surface performance offered by motorcycle tires (such as those described in WO 2021 / 090152) in the "super sport" segment, and has observed that these performances may be positively influenced by the fact that such tires have two alternating types of tread band portions in their central annular portion along the circumferential direction: one type has a high circumferential extension and is provided with circumferential grooves, while the other type has a reduced circumferential extension and is without grooves. The applicant believes that a similar alternation in the circumferential direction is also suitable in the tires of the present invention.

[0050] Therefore, the applicant believes that, in order to achieve all the objectives discussed above, it is recommended that the portion with reduced width be precisely positioned within the aforementioned circumferential groove and more precisely in the circumferential middle portion of the aforementioned circumferential groove, so as to alternately provide a tread band portion with a high circumferential extension and circumferential groove and a tread band portion with a reduced circumferential extension and no groove in the circumferential direction, which is similar to the aforementioned motorcycle tires in the "super sport" segment.

[0051] Therefore, the present invention relates to a motorcycle tire including a tread strip.

[0052] Preferably, the tread band includes a central annular portion that extends across the equatorial plane.

[0053] Preferably, the tire includes two lateral annular portions arranged on opposite sides relative to the central annular portion.

[0054] Preferably, the central annular portion includes multiple circumferential grooves.

[0055] Preferably, each circumferential groove includes a middle section.

[0056] Preferably, each circumferential groove includes two end portions arranged on opposite sides of the central portion in the circumferential direction.

[0057] Preferably, the width of the middle portion is less than the maximum width of each of the two end portions.

[0058] The applicant believes that the aforementioned type of sport touring motorcycle tire can combine the performance expected by the customer on wet surfaces with improved performance relative to the reference tire in terms of driving performance, grip and stability on dry surfaces.

[0059] According to the applicant, the improved performance on dry roads is achieved because the large contact force provided by the tire in the tire track area when the tire is driving on a dry road causes the circumferential grooves to close at the portions with reduced width.

[0060] Because the contact force in the tire track area under these driving conditions is lower than the contact force required to close the aforementioned section with reduced width, the desired performance on wet surfaces can actually be achieved. Therefore, the section with reduced width remains open to facilitate drainage.

[0061] Through road testing, the applicant even discovered a surprising improvement in grip on wet surfaces.

[0062] Without being bound by any explanatory theory, the applicant believes that this unexpected improvement may be due to the acceleration of water entering the circumferential trench at the section with reduced width, resulting in more efficient and immediate drainage.

[0063] The present invention may have at least one of the preferred features described below.

[0064] Preferably, the width of the central annular portion is equal to or less than the width of each of the two lateral annular portions.

[0065] Preferably, the two lateral annular portions have the same width.

[0066] Preferably, the width of the central annular portion is such that the ratio of the width to the maximum width of the radial section of the tire is less than 35%, more preferably less than 30%.

[0067] Preferably, the width of the central annular portion is such that the ratio of the width to the maximum width of the radial section of the tire is greater than 15%, more preferably greater than 20%.

[0068] In a preferred embodiment, the width of the central annular portion is such that the ratio of the width to the maximum width of the radial section of the tire is between 15% and 35%, preferably between 20% and 30%, for example equal to 25% or 26%.

[0069] Preferably, each lateral annular portion has a width such that the ratio of the width to the maximum width of the radial section of the tire is greater than 25%, more preferably greater than 30%.

[0070] Preferably, each lateral annular portion has a width such that the ratio of the width to the maximum width of the radial section of the tire is less than 45%, more preferably less than 40%.

[0071] In a preferred embodiment, each lateral annular portion has a width such that the ratio of the width to the maximum width of the radial section of the tire is between 25% and 45%, preferably between 30% and 40%, for example equal to 35% or 36%.

[0072] Preferably, the ratio of the width of the middle portion of each circumferential groove to the maximum width of each of the two end portions is greater than 0.4, more preferably greater than 0.45, and even more preferably greater than 0.5.

[0073] Preferably, the ratio of the width of the middle portion of each circumferential groove to the maximum width of each of the two end portions is less than 0.8, more preferably less than 0.75, and even more preferably less than 0.7.

[0074] In a preferred embodiment, the ratio of the width of the middle portion of each circumferential groove to the maximum width of each of the two end portions is between 0.4 and 0.8, preferably between 0.45 and 0.75, and even more preferably between 0.5 and 0.7.

[0075] Preferably, the ratio of the length of the middle portion of each circumferential groove to the length of each of the two end portions is greater than 0.8, more preferably greater than 0.9.

[0076] Preferably, the ratio of the length of the middle portion of each circumferential groove to the length of each of the two end portions is less than 1.2, more preferably less than 1.1, and even more preferably less than 1.

[0077] In a preferred embodiment, the ratio of the length of the middle portion of each circumferential groove to the length of each of the two end portions is between 0.8 and 1.2, preferably between 0.9 and 1.1, and more preferably between 0.9 and 1.

[0078] The applicant argues that the inclusion of a narrower middle section and end sections of the aforementioned width and length within the circumferential grooves allows for maximum tire performance on both dry and wet surfaces. In fact, the applicant believes that this arrangement of the two opposing surfaces of the circumferential grooves, spaced apart, allows them to contact each other at the narrower middle section on dry surfaces, thus improving grip on paved roads, while maintaining separation on wet surfaces, allowing the circumferential grooves to fully open and facilitating drainage. Furthermore, the two end sections of the grooves are wide enough to allow for an optimal trade-off between desired behavior on dry and wet surfaces.

[0079] Preferably, at least the end portion that enters the tire track area before the middle portion during tire rolling has a width that gradually decreases from the free end of the end portion toward the middle portion.

[0080] Preferably, each circumferential groove is arranged on the side of the equatorial plane.

[0081] Preferably, each circumferential groove includes an axial inner surface that is concave relative to the equatorial plane.

[0082] Preferably, the axial inner surface has a generally curved extension.

[0083] Preferably, the axial inner surface extends along a circumferential arc having a predetermined first radius of curvature and a center of curvature.

[0084] Preferably, the center of curvature is arranged on the opposite side of the equatorial plane.

[0085] Preferably, the first radius of curvature is greater than 100 mm, more preferably greater than 120 mm, and even more preferably greater than 140 mm.

[0086] Preferably, the first radius of curvature is less than 200 mm, more preferably less than 180 mm, and even more preferably less than 160 mm.

[0087] In a preferred embodiment, the first radius of curvature is between 100mm and 200mm, preferably between 120mm and 180mm, and more preferably between 140mm and 160mm.

[0088] Preferably, the plurality of circumferential grooves include a first series of circumferential grooves arranged on one side relative to the equatorial plane.

[0089] Preferably, the plurality of circumferential grooves include a second series of circumferential grooves arranged on the opposite side relative to the equatorial plane.

[0090] Preferably, the circumferential grooves in the first series of circumferential grooves are offset in the circumferential direction relative to the circumferential grooves in the second series of circumferential grooves.

[0091] Preferably, the shape of the circumferential groove in the second series of circumferential grooves is a mirror image of the shape of the circumferential groove in the first series of circumferential grooves.

[0092] Preferably, the offset of the circumferential groove in the circumferential direction makes the middle portion of each circumferential groove in the first series of circumferential grooves axially adjacent to the end portion of the corresponding circumferential groove in the second series of circumferential grooves.

[0093] Preferably, the offset of the circumferential groove in the circumferential direction is such that the middle portion of each circumferential groove in the second series of circumferential grooves is axially adjacent to the end portion of the corresponding circumferential groove in the first series of circumferential grooves.

[0094] The applicant has discovered that the offset described above ensures axial overlap between the circumferential grooves of the first series of circumferential grooves and the circumferential grooves of the second series of circumferential grooves, such that the portion of the circumferential groove with a reduced width is axially adjacent to the end portion of another circumferential groove. This allows for a favorable regularity in the tire's behavior during its rolling. This is beneficial not only for behavior on dry and wet surfaces but also for noise, vibration, and wear.

[0095] Preferably, the tread belt also includes a plurality of first lateral grooves. These first lateral grooves help to define a desired void-to-rubber ratio in the tread belt.

[0096] Preferably, the first lateral grooves have an axially inner portion disposed within the central annular portion. Therefore, when the tire is traveling on a wet surface, whether traveling in a straight line or turning, these first lateral grooves cooperate with the circumferential grooves to drain water from the tire track area.

[0097] Preferably, the first lateral groove has an axially outward portion disposed in one of the lateral annular portions so as to draw water away from the tire track area when the tire is traveling on a wet road surface.

[0098] Preferably, the width of the inner axial portion is less than the maximum width of the outer axial portion. Therefore, the behavior of the inner axial portion, as discussed above with reference to the portion of the circumferential groove with a reduced width, contributes to achieving the desired performance improvement on dry surfaces and the expected behavior on wet surfaces.

[0099] Preferably, the ratio of the width of the inner axial portion to the maximum width of the outer axial portion of each first transverse groove is greater than 0.4, more preferably greater than 0.45.

[0100] Preferably, the ratio of the width of the inner axial portion of each first transverse groove to the maximum width of the outer axial portion is less than 0.7, more preferably less than 0.65.

[0101] In a preferred embodiment, the ratio of the width of the axial inner portion to the maximum width of the axial outer portion of each first transverse groove is between 0.4 and 0.7, preferably between 0.45 and 0.65.

[0102] Preferably, the width of the axially outer portion gradually decreases from the axially inner portion toward the free end of the axially outer portion.

[0103] Preferably, the axial inner portion of each first transverse groove is shorter than the axial outer portion of the same first transverse groove.

[0104] Preferably, the ratio of the length of the axial inner portion of each first transverse groove to the length of the axial outer portion of the same first transverse groove is greater than 0.3.

[0105] Preferably, the ratio of the length of the inner axial portion of each first transverse groove to the length of the outer axial portion of the same first transverse groove is less than 0.5.

[0106] In a preferred embodiment, the ratio of the length of the axial inner portion of each first transverse groove to the length of the axial outer portion of the same first transverse groove is between 0.3 and 0.5.

[0107] The applicant believes that the numerical relationship between the width and length of the inner axial portion and the width and length of the outer axial portion of the first transverse groove allows for optimization of behavior on dry surfaces without adversely affecting behavior on wet surfaces.

[0108] Preferably, each of the first transverse grooves is arranged on the side of the equatorial plane.

[0109] Preferably, each first transverse groove includes an axially convex inner surface relative to the equatorial plane.

[0110] Preferably, the axial inner surface extends along a circumferential arc having a predetermined second radius of curvature and a center of curvature.

[0111] Preferably, the center of curvature is arranged on the same side relative to the equatorial plane.

[0112] Preferably, the second radius of curvature is smaller than the first radius of curvature.

[0113] Preferably, the ratio of the second radius of curvature to the first radius of curvature is greater than 0.2, more preferably greater than 0.3, and even more preferably greater than 0.4.

[0114] Preferably, the ratio of the second radius of curvature to the first radius of curvature is less than 0.8, more preferably less than 0.7, and even more preferably less than 0.6.

[0115] In a preferred embodiment, the ratio of the second radius of curvature to the first radius of curvature is between 0.2 and 0.8, preferably between 0.3 and 0.7, and more preferably between 0.4 and 0.6.

[0116] Preferably, the axial inner portion of each first transverse groove is arranged circumferentially between two successive circumferential grooves in the same series of circumferential grooves.

[0117] Preferably, the plurality of first transverse grooves include a first series of first transverse grooves arranged on one side relative to the equatorial plane.

[0118] Preferably, the plurality of first transverse grooves includes a second series of first transverse grooves arranged on the opposite side relative to the equatorial plane.

[0119] Preferably, the first transverse groove of the first series of first transverse grooves is offset relative to the first transverse groove of the second series of first transverse grooves in the circumferential direction.

[0120] Preferably, the axial inner portion of the first transverse groove of the first series of first transverse grooves is circumferentially offset relative to the axial inner portion of the first transverse groove of the second series of first transverse grooves.

[0121] Preferably, the axial inner portion of each first transverse groove in the first series is axially adjacent to the axial outer portion of the corresponding first transverse groove in the second series.

[0122] The offset of the first lateral groove affects the tire's behavior under both dry and wet conditions. Therefore, the considerations above regarding the offset of the circumferential groove also apply here.

[0123] Preferably, the tread band includes a plurality of second lateral grooves.

[0124] Preferably, the second lateral grooves are arranged entirely within the lateral annular portion. The second lateral grooves only enter the tire track area when the tire is turning and, under such driving conditions, facilitate drainage from the tire track area. They also help define the desired void-to-rubber ratio within the tread band.

[0125] Preferably, the plurality of second transverse grooves include a first series of second transverse grooves arranged on one side relative to the equatorial plane.

[0126] Preferably, the plurality of second transverse grooves include a second series of second transverse grooves arranged on the other side relative to the equatorial plane.

[0127] Preferably, the second transverse groove in the first series of second transverse grooves is offset in the circumferential direction relative to the second transverse groove in the second series of second transverse grooves.

[0128] Preferably, at least two of the second transverse grooves are arranged between two circumferentially successive first transverse grooves in the same series of first transverse grooves.

[0129] More preferably, the number of second transverse grooves between two circumferentially successive first transverse grooves arranged in the same series of first transverse grooves is greater than 2.

[0130] More preferably, the number of second transverse grooves between two circumferentially successive first transverse grooves arranged in the same series of first transverse grooves is less than 4.

[0131] In a preferred embodiment, the number of second transverse grooves between two circumferentially successive first transverse grooves arranged in the same series of first transverse grooves is between 2 and 4. Attached Figure Description

[0132] More features and advantages of the invention will become more apparent from the following description of some preferred embodiments of the invention with reference to the accompanying drawings. In these drawings:

[0133] - Figure 1 This is a schematic diagram of the radial section of the rear tire according to the present invention. For the sake of simplification, a grooveless tread band is shown.

[0134] - Figure 2 This is a front view of the rear tire according to the present invention;

[0135] - Figure 3 yes Figure 2 An enlarged view of a portion of the tire;

[0136] - Figure 4 yes Figure 2 An enlarged view of the central annular portion of the tire tread band;

[0137] - Figure 5 yes Figure 2 Another enlarged view of a portion of the tire. Detailed Implementation

[0138] refer to Figure 1 The motorcycle tire according to the present invention is indicated by reference numeral 1 in the accompanying drawings.

[0139] The following text is for reference only. Figure 1The descriptions also apply to both the rear tires and the front tires.

[0140] Tire 1 is a tire designed for motorcycles in the "sport touring" segment with large piston displacements as discussed above.

[0141] Tire 1 is intended to be mounted on a wheel rim with a mounting diameter between approximately 16 inches and approximately 21 inches.

[0142] In tire 1, the equatorial plane XX and the axis of rotation (not shown) are defined. Also defined is based on tire 1 ( Figure 2-5 The rotation direction R is arranged and is therefore parallel to the circumferential direction of the equatorial plane XX and perpendicular to the equatorial plane XX and / or parallel to the axis of rotation.

[0143] Tire 1 includes a carcass structure 2, which is formed by at least one carcass ply 3, which is made of an elastomeric material sheet, which incorporates multiple reinforcing cords (not shown) made of fibrous fabric material.

[0144] exist Figure 1 In the tire, the carcass structure 2 is of the radial type, that is, the reinforcing cords of the at least one carcass ply 3 are arranged substantially parallel to each other in the crown portion of the tire 1 at an angle relative to the circumferential direction, the angle being between 70° and 110°, more preferably between 80° and 100°, for example, an angle equal to 90°.

[0145] In an embodiment not shown, the carcass structure includes at least two carcass plies that are radially stacked on top of each other. In this case, the reinforcing cords are substantially parallel to each other in each carcass ply and are oriented in each carcass ply according to an inclination direction relative to the equatorial plane of the tire and according to the opposite direction of the reinforcing cords of the radially adjacent carcass ply 3 (cross-ply carcass).

[0146] The tire carcass structure 2 is typically coated with a sealing layer 100 (so-called "lining") on its inner wall. The sealing layer is mainly composed of an air-impermeable elastomeric material layer, which is suitable for ensuring the airtightness of the tire 1 itself after inflation.

[0147] The (or each) carcass ply 3 is shaped in a generally annular configuration and its axially opposite lateral edges 3a are turned upward on their respective annular reinforcing structures 4, designed to hold the tire 1 on the corresponding mounting rim (not shown). The annular reinforcing structure 4 is commonly referred to as the "bead core".

[0148] A conical elastomeric filler 5 is applied to the outer peripheral edge of the bead core 4, occupying the space between the corresponding carcass ply 3 and the corresponding upwardly turned lateral edge 3a of the carcass ply 3.

[0149] The area of ​​tire 1 including the bead core 4 and the elastomeric filler 5 forms a so-called bead 9, which is designed to anchor tire 1 to the rim.

[0150] Preferably, the carcass reinforcement structure can be located radially outward relative to the carcass structure (whether it is a radial ply or a cross ply). The carcass reinforcement structure includes a crown ply arranged radially outward relative to the outermost radial carcass ply and at least in the crown portion of the outermost radial carcass ply. The crown ply includes reinforcing elements arranged parallel to each other. The crown ply is arranged on the outermost radial carcass ply such that the reinforcing elements of the crown ply have an angle relative to the equatorial plane opposite to the angle of the reinforcing cords of the outermost radial carcass ply. Optionally, the carcass reinforcement structure further includes two ply layers arranged on opposite sides of the crown ply and not connected to corresponding bead layers.

[0151] In one embodiment, the (or each) carcass ply 3 is manufactured by juxtaposing multiple strips of elastomeric material reinforced by the aforementioned reinforcing cords.

[0152] The belt structure 6 is applied circumferentially to the carcass structure 2 at a radially external position relative to the carcass structure. The belt structure 6 includes at least one belt layer 6a, which is typically formed of fabric or metal-reinforced cords embedded in a layer of elastomeric material.

[0153] Preferably, the belt structure 6 is of the zero-degree type, that is, the belt layer 6a is made of reinforcing cords arranged substantially parallel and side by side to form multiple loops. These loops are oriented substantially in a circumferential direction (typically having an angle between 0° and 5°), which is generally defined as “zero degrees” with reference to the direction in which the loops are laid relative to the circumferential direction of the tire 1.

[0154] The belt layer 6a, typically defined as “zero degree”, may include an axially juxtaposed winding portion of a single reinforcing cord, or an axially juxtaposed winding portion of a rubberized strip-like element having reinforcing cords axially located on both sides.

[0155] The reinforcing cord of the zero-degree belt layer 6a is typically a metal cord made of high-carbon steel wire (i.e., steel wire with a carbon content of at least 0.6%-0.7%). Preferably, the metal reinforcing cord has a high elongation (HE).

[0156] Optionally, in some tires, such as Figure 1In order to improve the adhesion between the belt structure 6 and the tire carcass structure 2, an adhesive layer 7 of elastomeric material can be arranged between the belt structure and the tire carcass structure.

[0157] In various embodiments, the belt structure 6 comprises two or more radially stacked belt layers, each belt layer being made of an elastomeric material incorporating reinforcing cords arranged parallel to each other. The belt layers are arranged such that the reinforcing cords of the first belt layer are oriented obliquely relative to the equatorial plane of the tire, while the reinforcing cords of radially adjacent belt layers also have an oblique and intersecting orientation relative to the reinforcing cords of the first belt layer, forming a so-called "cross belt." The same applies if any other possible belt layers are present. Cross belts typically comprise fabric reinforcing cords.

[0158] The tread belt 8 is circumferentially stacked on the belt structure 6 and located radially outward relative to the belt structure 6.

[0159] During the molding operation performed in conjunction with the vulcanization step of tire 1, a plurality of grooves are obtained on the tread belt 8, which are oriented as discussed in the remainder of this specification in order to define a specific tread pattern. As already mentioned, for simplicity Figure 1 The diagram in the image does not show the aforementioned grooves.

[0160] The tread belt 8 (and other tire components not described / illustrated as they are standard parts) is made of an elastomer material.

[0161] Figure 1 The tire 1 also includes a pair of sidewalls 10, which are laterally applied to opposite sides of the tire carcass structure 2 and are also made of an elastomeric material.

[0162] refer to Figure 1 Tire 1 has a section height H, which is measured on the equatorial plane XX between the top of the tread strip 8 and the assembly diameter, which is identified by a reference line r passing through the bead 9 of tire 1.

[0163] refer to Figure 1 As measured on the equatorial plane XX of tire 1, tire 1 also has a maximum radial cross-sectional width C defined by the distance between the laterally opposite ends E of the tread belt 8, and an arrow f defined by the distance from the top of the tread belt 8 to the line L passing through the laterally opposite ends E. The laterally opposite ends E of the tread belt 8 may be formed with edges.

[0164] The maximum radial section width C of tire 1 is preferably between 120 mm and 200 mm. In the case of the front tire, the maximum radial section width C is more preferably equal to 120 mm, and in the case of the rear tire, the maximum radial section width C is equal to 180 mm.

[0165] Tire 1 has: a curvature ratio f / C defined by the ratio of arrow f to the maximum width C of the radial section; and an arrow-to-total-height ratio (f / H) defined by the ratio between arrow f and section height H.

[0166] When tire 1 is a rear tire, the arrow f is preferably between about 40 mm and about 60 mm, the curvature ratio f / C is preferably between about 0.25 and about 0.35, and the ratio of the arrow to the total height f / H is preferably between about 0.40 and about 0.60.

[0167] When tire 1 is the front tire, the arrow f is preferably between about 40 mm and about 60 mm, the curvature ratio f / C is preferably between about 0.3 and about 0.6, and the ratio of the arrow to the total height f / H is preferably between about 0.4 and about 0.7.

[0168] refer to Figures 2 to 5 The tread design of the tread belt 8 of a preferred embodiment of a tire 1 manufactured according to the present invention will be described below. In these figures, R denotes the rolling direction of the tire 1, and in the specific case shown herein, the tire is a rear tire. However, the following description is analogous to the case of a front tire.

[0169] The tread band 8 has a clearance rubber ratio between 7% and 14%, preferably between 8% and 13%, and more preferably between 9% and 12%. For example, in the case of a rear tire with a specification of 180 / 55 / R17, the clearance rubber ratio is equal to 10%, while in the case of a front tire with a specification of 120 / 70 / R17, the clearance rubber ratio is equal to 11.3%.

[0170] like Figure 2 and Figure 3 As shown, the tread band 8 includes a central annular portion A extending across the equatorial plane and two lateral annular portions S arranged on opposite sides relative to the central annular portion A.

[0171] The lateral annular portions S have the same width.

[0172] The width of the central annular portion A is equal to or less than the width of the lateral annular portion S.

[0173] The width of the central annular portion A is such that the ratio of this width to the maximum width C of the radial section is between 5% and 15%, for example, equal to 10%.

[0174] The width of each of the lateral annular portions S is such that the ratio of that width to the maximum width C of the radial section is between 42.5% and 47.5%, for example, equal to 45%.

[0175] like Figure 3 As shown, the axial inner annular portion A* of the central annular portion A does not have grooves. The axial inner annular portion A* is arranged straddling the equatorial plane XX.

[0176] The tread band 8 includes a plurality of circumferential grooves 20, 60, which are formed in the central annular portion A and arranged on opposite sides relative to the equatorial plane XX and located at the outermost position in the axial direction relative to the inner annular portion A*.

[0177] Specifically, the central annular portion A includes a first series of circumferentially successive grooves 20 arranged on one side relative to the equatorial plane XX and a second series of circumferentially successive grooves 60 arranged on the other side relative to the equatorial plane XX.

[0178] The shape of the circumferential groove 60 is a mirror image of the shape of the circumferential groove 20, and the dimensions of the circumferential groove 60 are the same as those of the circumferential groove 20.

[0179] The circumferential groove 20 is offset in the circumferential direction relative to the circumferential groove 60.

[0180] The following references are included in this instruction manual. Figure 4 A more detailed description is given of the circumferential grooves 20 and 60.

[0181] refer to Figure 2 and Figure 3 The tread belt 8 also includes a plurality of first lateral grooves 30, 70, which are arranged on opposite sides relative to the equatorial plane XX and located at the outermost position in the axial direction relative to the inner annular portion A*.

[0182] Specifically, the first series of circumferentially successive transverse grooves 30 are arranged on one side relative to the equatorial plane XX, while the second series of circumferentially successive transverse grooves 70 are arranged on the other side relative to the equatorial plane XX.

[0183] The shape of the first transverse groove 70 is a mirror image of the shape of the first transverse groove 30, and the size of the first transverse groove 70 is the same as the size of the first transverse groove 30.

[0184] Each first transverse groove 30 is arranged circumferentially between two corresponding circumferentially successive circumferential grooves 20. Similarly, each first transverse groove 70 is arranged circumferentially between two corresponding circumferentially successive circumferential grooves 60.

[0185] The first transverse groove 30 is offset in the circumferential direction relative to the first transverse groove 70.

[0186] The following references are included in this instruction manual. Figure 5 The first transverse grooves 30 and 70 are described in more detail.

[0187] refer to Figure 2 and Figure 3 The tread band 8 also includes a plurality of second lateral grooves 41, 42, 43; 81, 82, 83, which are arranged on opposite sides relative to the equatorial plane XX and are located at the outermost position in the axial direction relative to the central annular portion A.

[0188] Specifically, the first series of three circumferentially successive second transverse grooves 41, 42, 43 are arranged on one side relative to the central annular portion A, and the second series of three circumferentially successive second transverse grooves 81, 82, 83 are arranged on the other side relative to the central annular portion A.

[0189] The shapes of the three second transverse grooves 81, 82, and 83 are mirror images of the shapes of the three second transverse grooves 41, 42, and 43, and the dimensions of the three second transverse grooves 81, 82, and 83 are the same as the dimensions of the three second transverse grooves 41, 42, and 43.

[0190] Three second transverse grooves 41, 42, and 43 are arranged circumferentially between two corresponding circumferentially successive first transverse grooves 30. Similarly, three second transverse grooves 81, 82, and 83 are arranged circumferentially between two corresponding circumferentially successive first transverse grooves 70.

[0191] The three second transverse grooves 41, 42, and 43 are offset in the circumferential direction relative to the three second transverse grooves 81, 82, and 83.

[0192] The following is a reference in this instruction manual. Figure 3 The second transverse grooves 41, 42, 43 and 81, 82, 83 are described in more detail.

[0193] Details regarding circumferential grooves 20 and 60 are provided below.

[0194] like Figure 4 As shown, each circumferential groove 20 includes an intermediate portion 21 circumferentially arranged between two opposing end portions 22, 23. Similarly, each circumferential groove 60 includes an intermediate portion 61 circumferentially arranged between two opposing end portions 62, 63.

[0195] During the rolling of tire 1, the end portions 22 and 62 enter the tire track area before the middle portions 21 and 61 and the end portions 23 and 63.

[0196] End portions 22 and 62 include free ends 22a and 62a and opposite ends, the free ends being arranged at a distance D1 from the equatorial plane, and the opposite ends being connected to intermediate portions 21 and 61 and located at a distance D3 from the equatorial plane. Similarly, end portions 23 and 63 include free ends 23a and 62a and opposite ends, the free ends being arranged at a distance D2 from the equatorial plane, and the opposite ends being connected to intermediate portions 21 and 61 and located at a distance D3 from the equatorial plane.

[0197] Preferably, the ratio of distance D1 to distance D2 is between 0.1 and 3.

[0198] Preferably, the ratio of distance D1 to distance D3 is between 0.2 and 1.

[0199] In a preferred embodiment, the distance D1 is between 5 mm and 15 mm, the distance D2 is between 10 mm and 20 mm, and the distance D3 is between 25 mm and 35 mm.

[0200] In some embodiments, distance D2 is substantially equal to distance D1.

[0201] The width W1a of the middle portions 21 and 61 is smaller than the maximum width W1b of the corresponding end portions 22 and 62, and also smaller than the maximum width W1c of the corresponding end portions 23 and 63. In particular, the ratio of width W1a to the maximum width W1b and the ratio of width W1a to the maximum width W1c are between 0.4 and 0.8, preferably between 0.45 and 0.75, and more preferably between 0.5 and 0.7.

[0202] like Figure 4 As shown, the end portions 22 and 62 have a width W1b, which gradually decreases from the middle portions 21 and 61 toward the free ends 22a and 62a.

[0203] The length L1a of the middle portions 21 and 61 is substantially equal to the length L1b of the corresponding end portions 22 and 62, and also substantially equal to the length L1c of the corresponding end portions 23 and 63. In particular, the ratio of length L1a to length L1b and the ratio of length L1a to length L1c are between 0.8 and 1.2, preferably between 0.9 and 1.1, and more preferably between 0.9 and 1.

[0204] Each circumferential groove 20, 60 is arranged beside the equatorial plane XX and has an axial inner surface 20a, 60a, which is concave relative to the equatorial plane XX and has a generally curved extension. In particular, each axial inner surface 20a, 60a extends along a corresponding circumferential arc having a radius of curvature R1 and a center of curvature C1 arranged on opposite sides relative to the equatorial plane XX.

[0205] The radius of curvature R1 is preferably between 100 mm and 200 mm, more preferably between 120 mm and 180 mm, and even more preferably between 140 mm and 160 mm.

[0206] As already mentioned, the circumferential groove 20 is offset in the circumferential direction relative to the circumferential groove 60. In other words, each circumferential groove 20 only partially overlaps the corresponding circumferential groove 60 in the axial direction.

[0207] Specifically, the offset of circumferential grooves 20 and 60 in the circumferential direction makes:

[0208] - The middle portion 21 of each circumferential groove 20 is axially adjacent to the end portion 61 of the corresponding circumferential groove 60;

[0209] - The middle portion 61 of each circumferential groove 60 is axially adjacent to the end portion 22 of the corresponding circumferential groove 20;

[0210] - The end portion 23 of each circumferential groove 20 is arranged at the corresponding axial portion of the tread belt 8 that is not provided with circumferential groove portion 60;

[0211] - The end portion 62 of each circumferential groove 60 is arranged at the corresponding axial portion of the tread belt 8 that is not provided with the circumferential groove portion 20.

[0212] Details regarding the first transverse grooves 30 and 70 are provided below.

[0213] like Figure 5 As shown, each first transverse groove 30, 70 includes: a corresponding axial inner portion 31, 71 arranged in the central annular portion A and on the side of the equatorial plane XX; and a corresponding axial outer portion 32, 72 arranged in the corresponding lateral annular portion S.

[0214] The axial inner portion 31 of each first transverse groove 30 is arranged circumferentially between two corresponding circumferentially successive circumferential grooves 20. Similarly, the axial inner portion 71 of each first transverse groove 70 is arranged circumferentially between two corresponding circumferentially successive circumferential grooves 60.

[0215] The width W2a of the axial inner portion 31, 71 of each first transverse groove 30, 70 is less than the maximum width W2b of the axial outer portion 32, 72 of the first transverse groove 30, 70. In particular, the ratio of width W2a to maximum width W2b is between 0.4 and 0.7, preferably between 0.45 and 0.65.

[0216] The width W2a is basically constant along the entire axial inner portion 31, 71, while the width W2b gradually decreases from the axial inner portion 31, 71 toward the free ends 32a, 72a of the axial outer portion 32, 72.

[0217] The length L2a of the inner axial portions 31 and 71 is less than the length L2b of the outer axial portions 32 and 72. In particular, the ratio of length L2a to length L2b is between 0.3 and 0.5.

[0218] Each first transverse groove 30, 70 has an axial inner surface 30a, 70a, which is convex relative to the equatorial plane XX and has a generally curved extension. In particular, each axial inner surface 30a, 70a extends along a corresponding circumferential arc having a radius of curvature R2 and a center of curvature C2 arranged on the same side relative to the equatorial plane XX.

[0219] The ratio of the radius of curvature R2 to the radius of curvature R1 is preferably between 1.2 and 0.4, more preferably between 1 and 0.6, and even more preferably between 0.9 and 0.7.

[0220] In the example shown in this article, the radius of curvature R2 is smaller than the radius of curvature R1.

[0221] As already mentioned, the first transverse groove 30 is offset circumferentially relative to the first transverse groove 70. In other words, each first transverse groove 30 only partially overlaps the corresponding first transverse groove 70 in the axial direction.

[0222] Specifically, the circumferential offset of the first transverse grooves 30 and 70 makes:

[0223] - The axial inner portion 31 of each first transverse groove 30 is offset in the circumferential direction relative to the axial inner portion 71 of the corresponding first transverse groove 70, and vice versa.

[0224] - The axial inner portion 31 of each first transverse groove 30 is axially adjacent to a portion of the axial outer portion 72 of the first transverse groove 70 described above;

[0225] - A portion of the axially outer portion 32 of each first transverse groove 30 is axially adjacent to the end portion 61 of the corresponding circumferential groove 60 and partially overlaps in the axial direction on the remainder of the axially outer portion 72 of the corresponding first transverse groove 70.

[0226] - The remaining portion of the axially outer portion 32 of each first transverse groove 30 is axially adjacent to the end portion 22 of the corresponding circumferential groove 20 and partially overlaps the middle portion 61 of the corresponding circumferential groove 60 in the axial direction.

[0227] - The axial inner portion 72 of each first transverse groove 70 is not axially adjacent to the corresponding first transverse groove 30.

[0228] Details regarding the second transverse grooves 41, 42, 43 and 81, 82, 83 are provided below.

[0229] Despite Figure 2 , 3 In the example shown in Figure 5, a group of three second transverse grooves 41, 42, and 43 arranged circumferentially between two consecutive first transverse grooves 30 is provided, and a group of three second transverse grooves 81, 82, and 83 arranged circumferentially between two consecutive first transverse grooves 70 is provided. However, the number of second transverse grooves in each of the above groups can also be two or four.

[0230] refer to Figure 3 The second lateral grooves 41, 42, 43 and 81, 82, 83 are completely arranged in the lateral annular portion S of the tread band 8.

[0231] The circumferential extension of the second transverse grooves 41, 42, 43 and 81, 82, 83 is less than the circumferential extension of the circumferential grooves 20, 60 and less than the circumferential extension of the first transverse grooves 30, 70.

[0232] As already mentioned, the second transverse grooves 41, 42, 43 are offset in the circumferential direction relative to the second transverse grooves 81, 82, 83.

[0233] Specifically, the circumferential offset between the second transverse grooves 41, 42, 43 and the second transverse grooves 81, 82, 83 results in:

[0234] - Each second transverse groove 41 is axially adjacent to the corresponding first transverse groove 30;

[0235] - Each second transverse groove 81 is axially adjacent to the corresponding first transverse groove 70;

[0236] - Each second transverse groove 43 is axially adjacent to the corresponding circumferential groove 20;

[0237] - Each second transverse groove 83 is axially adjacent to the corresponding circumferential groove 60;

[0238] - Each second transverse groove 42 is circumferentially arranged between the corresponding second transverse groove 41 and the corresponding second transverse groove 43, and a portion thereof is partially superimposed on the end portion 23 of the corresponding circumferential groove 20 in the axial direction, and the remainder is superimposed on the axial inner portion 71 of the corresponding first transverse groove 70 in the axial direction.

[0239] - Each second transverse groove 82 is circumferentially arranged between the corresponding second transverse groove 81 and the corresponding second transverse groove 82, and a portion thereof is superimposed on the end portion 23 of the corresponding circumferential groove 60 in the axial direction, while the remainder is superimposed on the end portion 23 of the corresponding circumferential groove 20 in the axial direction.

[0240] Comparative Test

[0241] The applicant manufactured a sample of a rear tire 1 according to an embodiment of the present invention, the sample specifically having Figures 2 to 5 The tire tread design is shown below. In the following text, this tire is designated as INV.

[0242] The tire INV has the same construction and dimensions as a rear tire (hereinafter referred to as Ref) currently sold by the applicant for sport touring motorcycles, and the Ref tire is also well received by consumers for its excellent performance on both dry and wet surfaces.

[0243] This test was conducted by mounting tires INV and Ref (inflated at the same pressure) on the rear wheel of a Kawasaki Versys 1000 motorcycle and the same tires on the front wheel, under substantially the same environmental conditions. The tests were conducted under conditions defined as “cold” (i.e., asphalt temperature and ambient temperature both between 10°C and 15°C) and under conditions defined as “hot” (i.e., asphalt temperature between 40°C and 50°C, and ambient temperature between 27°C and 37°C).

[0244] The behavior of both tires (INV and Ref) was evaluated on both dry and wet surfaces, and rider feedback was solicited. Specifically, the items listed in Table 1 below were evaluated, along with rider feedback.

[0245] The test was conducted by driving on a route with straight sections and curves.

[0246] Table 1

[0247] In Table 1, “=" indicates a positive rating obtained using tire Ref, “+” indicates an improvement relative to tire Ref, and “++” indicates a significant improvement relative to tire Ref.

[0248] Table 1 shows that the performance offered by tire INV is essentially the same as that of the already excellent tire Ref in terms of driving performance and water drainage on wet roads, with a remarkable improvement in grip on wet roads.

[0249] In terms of stability, the tire INV also performed better, and it was much better in terms of driving performance and grip on dry surfaces, thus confirming that the applicant's goal of allowing for more sporty driving, tending towards the driving performance allowed by motorcycle tires in the "super sport" segment, has been achieved.

[0250] Of course, those skilled in the art can make further modifications and alterations to the tires of the above invention to meet specific and situation-dependent application needs, and such modifications and alterations shall in any case fall within the protection scope defined by the following claims.

Claims

1. A motorcycle tire (1) comprising a tread belt (8) having a central annular portion (A) extending across the equatorial plane (XX) of the motorcycle tire (1) and two lateral annular portions (S) arranged on opposite sides relative to the central annular portion (A), wherein, The central annular portion (A) includes a plurality of circumferential grooves (20; 60), each circumferential groove having a central portion (21; 61) and two end portions (22, 23) arranged on opposite sides of the central portion (21; 61) in the circumferential direction. 62, 63), wherein the width (W1a) of the middle portion (21; 61) is smaller than that of the two end portions (22, 23); The maximum width (W1b, W1c) of each of (62, 63).

2. The motorcycle tire (1) according to claim 1, wherein, The width (W1a) of the middle portion (21; 61) and the width of the two end portions (22, 23; The ratio of the maximum widths (W1b, W1c) of each of 62, 63) is between 0.4 and 0.

8.

3. The motorcycle tire (1) according to claim 1 or 2, wherein, The length (L1a) of the middle portion (21; 61) and the length of the two end portions (22, 23; The ratio of the lengths (L1b, L1c) of each of 62, 63 is between 0.8 and 1.

2.

4. The motorcycle tire (1) according to any one of the preceding claims, wherein, Each circumferential groove (20; 60) is arranged beside the equatorial plane (XX) and includes an axial inner surface (20a; 60a) that is concave relative to the equatorial plane (XX) and extends along a circumferential arc having a predetermined first radius of curvature (R1) and a center of curvature (C1) arranged on the opposite side relative to the equatorial plane (XX).

5. The motorcycle tire (1) according to any one of the preceding claims, wherein, The plurality of circumferential grooves (20; 60) include a first series of circumferential grooves (20) arranged on one side relative to the equatorial plane (XX) and a second series of circumferential grooves (60) arranged on the other side relative to the equatorial plane (XX), wherein the circumferential grooves (20) in the first series of circumferential grooves (20) are offset in the circumferential direction relative to the circumferential grooves (60) in the second series of circumferential grooves (60) such that the middle portion (21) of each circumferential groove (20) in the first series of circumferential grooves (20) is axially adjacent to the end portion (63) of the corresponding circumferential groove (60) in the second series of circumferential grooves (60), and the middle portion (61) of each circumferential groove (60) in the second series of circumferential grooves (60) is axially adjacent to the end portion (22) of the corresponding circumferential groove (20) in the first series of circumferential grooves (20).

6. The motorcycle tire (1) according to any one of the preceding claims, wherein, The tread band (8) further includes a plurality of first lateral grooves (30; 70), the plurality of first lateral grooves having an axially inner portion (31; 71) arranged in the central annular portion (A) and an axially outer portion (32; 72) arranged in one of the lateral annular portions (S), wherein the width (W2a) of the axially inner portion (31; 71) is less than the maximum width (W2b) of the axially outer portion (32; 72).

7. The motorcycle tire (1) according to claim 6, wherein, The ratio of the width (W2a) of the inner axial portion (31; 71) to the maximum width (W2b) of the outer axial portion (32; 72) is between 0.4 and 0.

7.

8. The motorcycle tire (1) according to claim 6 or 7, wherein, The axial inner portion (31; 71) of each of the first transverse grooves (30; 70) is shorter than the axial outer portion (32; 72) of the same first transverse groove (30; 70).

9. The motorcycle tire (1) according to any one of claims 6 to 8, wherein, Each first transverse groove (30; 70) is arranged beside the equatorial plane (XX) and includes an axial inner surface (30a, 70a), which is convex relative to the equatorial plane (XX) and extends along a circumferential arc having a predetermined second radius of curvature (R2) and a center of curvature (C2) arranged on the same side relative to the equatorial plane (XX).

10. The motorcycle tire (1) according to any one of claims 6 to 9 when subordinate to claim 5, wherein, The axial inner portion (31; 71) of each first transverse groove (30; 70) is arranged circumferentially between two successive circumferential grooves (20; 60) of the same series of circumferential grooves (20; 60).

11. The motorcycle tire (1) according to any one of claims 6 to 10, wherein, The plurality of first transverse grooves (30; 70) include a first series of first transverse grooves (30) arranged on one side relative to the equatorial plane (XX) and a second series of first transverse grooves (70) arranged on the other side relative to the equatorial plane (XX), wherein the first transverse grooves (30) of the first series of first transverse grooves (30) are offset in the circumferential direction relative to the first transverse grooves (70) of the second series of first transverse grooves (70).

12. The motorcycle tire (1) according to claim 11, wherein, The axial inner portion (31) of the first transverse groove (30) of the first series is circumferentially offset relative to the axial inner portion (71) of the first transverse groove (70) of the second series.

13. The motorcycle tire (1) according to claim 12, wherein, The axial inner portion (31) of each first transverse groove (30) of the first series of first transverse grooves (30) is axially adjacent to the axial outer portion (72) of the corresponding first transverse groove (70) of the second series of first transverse grooves (70).

14. The motorcycle tire (1) according to any one of claims 6 to 13, wherein, The tread band (8) includes a plurality of second lateral grooves (41, 42, 43; 81, 82, 83) that are fully arranged in the lateral annular portion (S).

15. The motorcycle tire (1) according to claim 14, wherein, The plurality of second transverse grooves (41, 42, 43; 81, 82, 83) include a first series of second transverse grooves (41, 42, 43) arranged on one side relative to the equatorial plane (XX) and a second series of second transverse grooves (81, 82, 83) arranged on the other side relative to the equatorial plane (XX), wherein the second transverse grooves (41, 42, 43) of the first series of second transverse grooves (41, 42, 43) are offset in the circumferential direction relative to the second transverse grooves (81, 82, 83) of the second series of second transverse grooves (81, 82, 83).

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