Off-road motorcycle tyre

Abstract

An off-road motorcycle tyre comprises a tread band having a central annular portion extending astride of an equatorial plane (X-X) of the tyre (1) and comprising: - a plurality of circumferentially consecutive central blocks (15) arranged astride of the equatorial plane (X-X) and having a first width (LI) in the axial direction; - a plurality of circumferentially consecutive first lateral blocks (20) arranged next to the central blocks (15) and having a second width (L2) in the axial direction; - a plurality of circumferentially consecutive second lateral blocks (60) arranged next to the central blocks (15) on the opposite side with respect to said plurality of first lateral blocks (20) and having said second width (L2) in the axial direction; wherein the ratio between said second width (L2) and said first width (LI) is comprised between 0.65 and 1.3.

Description

[0001] Off-road motorcycle tyre

[0002] DESCRIPTION

[0003] The present invention relates to a tyre for off-road motorcycles, or for motorcycles of the "Motocross" type.

[0004] Preferably, the tyre of the invention is intended to be mounted on the rear wheel of motorcycles of the "Motocross" type, which, as known, are motorcycles intended to be used off-road. These motorcycles may have medium-large piston displacement (such as 450 cc or more) or lower piston displacement (such as 125 cc or 250 cc).

[0005] Motorcycles of the "Motocross" type also comprise so-called "Minicross" motorcycles, which typically have piston displacement comprised between 65 cc and 85 cc.

[0006] Examples of motorcycles of the "Motocross" type of medium-large piston displacement are:

[0007] - KTM 450 SX-F, having a piston displacement equal to 450 cc, power equal to 63 hp, maximum torque equal to 53 Nm and mass equal to 104 KG;

[0008] - Honda CRF450R, having a piston displacement equal to 450 cc, power equal to 52 hp, maximum torque equal to 47 Nm and mass equal to 106 KG.

[0009] The tyre of the present invention is approved for off-road use primarily during professional and amateur competitions.

[0010] PRIOR ART

[0011] Tyres intended for motorcycles of the "Motocross" type are typically used in extreme conditions, with highly differentiated types of terrain other than asphalt: sandy, rocky, compact, etc. In particular, in the case of use during a competition, the conditions of use of these tyres become very harsh, and the tyres must guarantee excellent performance in terms of durability, tear resistance, grip, stability and traction on such differentiated terrains, even at high speeds.

[0012] Typically, tyres having a tread pattern defined by a plurality of blocks arranged either on a central annular portion of the tread band and on opposite lateral and / or shoulder annular portions of the tread band are used in this product segment. These blocks are capable of penetrating the terrain (particularly sandy or soft or medium-soft terrain) to ensure traction, particularly during acceleration and braking.

[0013] Examples of some tyres of the type described above and produced by Pirelli Tyre S.p.a. are: MX Extra X, MX 32 MidHard, XC MidHard, MC MidHard, MX32 MidSoft, XC MidSoft, MC360 MidSoft.

[0014] Further examples are disclosed in US 6651711 B2, US 20082457A1, EP 2374636B1, EP 2529954 Bl, EP 3047981 Bl, US 2015165826 Al, EP 3006232 Bl, EP 3339057 Bl, EP 3501853 Bl, CN 208053001 U, CN 211222917 U.

[0015] SUMMARY OF THE INVENTION

[0016] Throughout the present description and in the following claims, when reference is made to certain values of certain angles, these values are deemed to be absolute values, i.e. both positive values and negative values with respect to a reference plane or direction, unless specified otherwise.

[0017] Moreover, 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 aforementioned range, unless expressly stated otherwise.

[0018] Moreover, all of the ranges include any combination of the described minimum and maximum values and also include any intermediate range, even if not expressly described specifically.

[0019] 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.

[0020] Hereinafter, the following definitions apply.

[0021] The term "equatorial plane" of the tyre is used to indicate a plane perpendicular to the rotation axis of the tyre and that divides the tyre into two equal parts.

[0022] The term "motorcycle tyre" is used to indicate a tyre having a high curvature ratio, typically greater than 0.20.

[0023] The term "curvature ratio" is used to indicate the ratio between the distance comprised between the radially highest point of the tread band and the maximum width of radial section of the tyre (such distance also being identified as "arrow"), and the same maximum width of the tyre, in a cross section thereof.

[0024] The term "maximum width of radial section", or "maximum chord", is used to indicate the maximum width of the profile of the tyre, i.e. the length of the segment having as its ends the two axially outermost points of the profile of the tread band.

[0025] The term "circumferential extension" of the tyre, or of the tread band or of portions thereof, is used to indicate the extension in plan of the outer base surface of the tread band or of portions thereof, on a plane tangent to the tyre. The circumferential extension has a length that can be measured at the equatorial plane.

[0026] The term "tread pattern" is used to indicate the representation of all the points of the tread band on a plane perpendicular to the equatorial plane of the tyre and tangent to the maximum diameter of the tyre. The tread pattern is defined by the plurality of blocks, possibly including recesses, and by a plurality of longitudinal and transversal cavities or grooves or channels that separate the various blocks from each other.

[0027] The term "block" is used to indicate a portion of tread band protruding from the outer base surface of the tread band by a height not shorter than 13 mm. The block is delimited, on at least two of its sides, by respective grooves and, on two of its other sides, either by a respective groove or by a respective connecting element. In case the block is positioned on the axially outermost portion of the tread band, it is delimited in the axial direction by the axially outermost face of the tread band and, in the axially innermost position, by at least one groove.

[0028] The term "cavity" or "groove" or "channel" is used to indicate a furrow formed on the tread band and delimiting a block. The base surface of the groove lies on the outer base surface of the tread band. Therefore, the groove has a height equal to the distance between the outer base surface of the tread band and the top surface of at least one of the adjacent blocks.

[0029] The term "recess" is used to indicate a furrow formed in a block and having a depth lower than the depth of the block. The recess therefore has a depth lower than the height of the grooves.

[0030] The sizes of angles, and / or linear quantities (distances, widths, lengths, etc.) and / or surfaces are deemed as referred to the tread band or to the tread pattern as defined above.

[0031] 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.

[0032] The terms "circumferential" and "circumferentially" are used with reference to the direction of circumferential extension 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.

[0033] The expressions "axially inner" and "axially outer" indicate a position respectively closer to, and farther from, the equatorial plane with respect to a reference element. Thus, for example, a first face of a block is axially inner with respect to a second face of the block when the axial distance of the first face from the equatorial plane is shorter than that of the second face. Similarly, a first face of a block is axially outer with respect to a second face of the block when the axial distance of the first face from the equatorial plane is greater than that of the second face.

[0034] The term "width" is used to indicate a dimension measured along a direction perpendicular to the equatorial plane, i.e. along an axial direction.

[0035] The term "length" is used to indicate a dimension measured along a direction lying on, or parallel to, the equatorial plane, i.e. along a circumferential direction.

[0036] The term "axial distance" between two blocks is used, in case the faces of the two blocks facing each other are not flat, to indicate the distance measured along the axial direction at the points of a block that are closest to the adjacent block nearest to those points. This distance therefore corresponds to the minimum axial distance between the two blocks. Thus, the axial distance between two blocks is measured at the points of the blocks where the blocks have the maximum width in the axial direction.

[0037] The term "circumferential distance" between two blocks is used, in case the faces of the two blocks facing each other are not flat, to indicate the distance measured along the circumferential direction at the points of a block that are closest to the adjacent block nearest to those points. This distance therefore corresponds to the minimum circumferential distance between the two blocks. Therefore, the axial distance between two blocks is measured at the points of the blocks where the blocks have the maximum length in the circumferential direction. A block is considered "aligned" to another block in the axial direction when the centres of gravity of the two blocks lie on the same plane perpendicular to the equatorial plane of the tyre.

[0038] Instead, a block is considered "aligned" to another block in the circumferential direction when the centres of gravity of the two blocks lie on a single plane parallel to the equatorial plane of the tyre or on two planes parallel to the equatorial plane of the tyre and placed at a mutual axial distance shorter than 15% of the maximum chord of the tread band.

[0039] A block is "arranged next to" another block if the projections on the equatorial plane of at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80%, of the circumferential extensions of the two blocks coincide.

[0040] With reference to the angular arrangement of the blocks or of a face of the block (or of a portion of such a face) with respect to the equatorial plane of the tyre, such an angular arrangement is deemed for each point of the block or of the face of the block (or of a portion of such a face) as referring to the angle, comprised in an absolute value between 0° and 90°, formed by carrying out a rotation that, starting from the direction defined in the tread pattern by the equatorial plane, proceeds up to the direction tangent to the block and passing through such point. In the case the reference plane is not the equatorial plane but a plane perpendicular to the equatorial plane, the values of the angles are complementary to those measured with reference to the equatorial plane.

[0041] The size referred to circumferential lengths of grooves or blocks that intersect the equatorial plane of the tyre are taken at the equatorial plane of the tyre.

[0042] With reference to the faces of a block, a face of a block is "flat" if all its points lie on the same plane, while it is "concave" towards the inside of the block if the segment joining two opposite edges of the block is not entirely contained within the block. The concavity can be defined by a single curved surface or by at least two rectilinear surfaces inclined with respect to each other.

[0043] 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 greater than 10°.

[0044] The term "void to solid ratio" is used to indicate the ratio between the overall surface of the grooves of a given annular portion of the tread band or tread pattern of the tyre (possibly of the entire tread band or tread pattern) and the surface of the given portion of tread band or tread pattern (possibly of the entire tread band or tread pattern). This ratio coincides with the complement to 1 of the ratio between the sum of the top surfaces of the blocks of a given portion of the tread band (possibly of the entire tread band) and the total area of said given portion of the tread band (possibly of the entire tread band).

[0045] The term "footprint area" of the tyre is used to indicate the portion of the tyre in contact with the ground when the tyre is mounted on a wheel rim and a predetermined vertical load is exerted on the tyre.

[0046] Hereinafter, it is understood that a flat face, or a portion or part or wall thereof, of a block may also be slightly curved, such curve being interpolate by a plane tangent to the curve at any point or by a plane on which the ends of that curve lie.

[0047] The expression "module", when referred to a tread band, and in particular to the tread pattern, is used to indicate a portion of tread pattern repeated identically in succession along the entire circumferential extension of the tread band. The modules, whilst keeping the same pattern configuration, can nevertheless have different circumferential lengths.

[0048] The Applicant has taken into consideration motorcycles of the "Motocross" type, which, as already said, are widely used in off-road.

[0049] The Applicant observed that in order to optimally cover their entire range of use, these motorcycles should be equipped with tyres capable of ensuring high performance in terms of traction (both in acceleration and braking), driving stability and durability, both on hard and soft terrain.

[0050] The Applicant observed that, in accordance with customer demands, the market has recently been moving towards extremely specialised solutions, with several types of tyres for motorcycles of the "Motocross" type, each of these types being focused on a particular type of terrain.

[0051] Consistently, the Applicant proposed some tyres for motorcycles of the "Motocross" type suitable for off-road use on hard terrain, other tyres for motorcycles of the "Motocross" type suitable for off-road use on medium-hard terrain, further tyres for motorcycles of the "Motocross" type suitable for off-road use on medium-soft terrain, other tyres for motorcycles of the "Motocross" type suitable for off-road use on soft terrain.

[0052] The Applicant has recently focused its attention on rear tyres for motorcycles of the "Motocross" type designed for off-road use on medium-soft terrain.

[0053] The Applicant noted that these tyres are required to have, among other things, a high driving stability during the shift between driving along a straight course and driving along a bend and vice versa. This is in fact a performance characteristic that, if not specifically and properly considered, is likely to be heavily penalised by the reduced consistency and compactness of the terrain on which the tyre is intended to be used.

[0054] The Applicant focused on how this performance characteristic could be maximised, while trying not to penalise others.

[0055] The Applicant thought that in order to maximise the driving stability during the shift between driving along a straight course and driving along a bend, and vice versa, in rear tyres intended to be used on medium-soft terrain, the blocks in the central annular portion of the tread band should be sized appropriately.

[0056] In this regard, the Applicant has realized that in order to achieve a sufficiently comfortable driving transition, without therefore feeling undesirable steps while shifting from driving along a straight course and driving along a bend, and vice versa, it is advisable to provide a circumferential row of central blocks arranged astride of the equatorial plane and two circumferential rows of lateral blocks arranged on opposite sides of the circumferential row of central blocks, and to define the axial dimensions of each of the central blocks in relation to those of the lateral blocks and vice versa, taking care to provide, for all the aforementioned blocks, axial dimensions that are not very different, such that the ratio between the axial dimension of the lateral blocks and the axial dimension of the central blocks is within a predetermined range of values close to 1.

[0057] According to the Applicant, an arrangement such as the one described above does not penalise other performance characteristics on medium-soft terrain and brings similar benefits on harder, more compact terrain.

[0058] The present invention relates to an off-road motorcycle tyre comprising a tread band having a central annular portion extending astride of an equatorial plane of the tyre and two shoulder annular portions arranged on opposite sides of the central annular portion.

[0059] Preferably, the central annular portion comprises a plurality of circumferentially consecutive central blocks arranged astride of the equatorial plane.

[0060] Preferably, said central blocks have a first width in the axial direction.

[0061] Preferably, the central annular portion comprises a plurality of circumferentially consecutive first lateral blocks arranged next to the central blocks.

[0062] Preferably, the first lateral blocks have a second width in the axial direction.

[0063] Preferably, the central annular portion comprises a plurality of circumferentially consecutive second lateral blocks arranged next to the central blocks on the opposite side with respect to said plurality of first lateral blocks.

[0064] Preferably, the second lateral blocks have said second width in the axial direction.

[0065] Preferably, the ratio between said second width and said first width is comprised between 0.65 and 1.3.

[0066] The Applicant believes that a tread pattern made as described above allows tyres for motorcycles of the "Motocross" type designed to perform on medium-soft terrain to achieve excellent performance in terms of driving stability not only on medium-soft terrain but also on harder terrain, without at the same time affecting the other performance characteristics typically required to this type of tyre.

[0067] The present invention can have at least one of the preferred characteristics described hereinafter.

[0068] Preferably, the ratio between said second width and said first width is greater than 0.7.

[0069] Preferably, the ratio between said second width and said first width is less than 1.2.

[0070] In particularly preferred embodiments, the ratio between said second width and said first width is comprised between 0.7 and 1.2.

[0071] Preferably, said tread band has a maximum chord.

[0072] In some preferred embodiments, the ratio between said first width and said maximum chord is less than 0.25.

[0073] In that case, preferably, the ratio between said first width and said maximum chord is greater than 0.15.

[0074] In all the preferred embodiments, the ratio between said first width and said maximum chord is comprised between 0.15 and 0.25. In some preferred embodiments, the ratio between said second width and said maximum chord is greater than 0.19.

[0075] In that case, preferably, the ratio between said second width and said maximum chord is less than 0.21.

[0076] In all the preferred embodiments, the ratio between said second width and said maximum chord is comprised between 0.19 and 0.21.

[0077] The Applicant believes that sizing the central and lateral blocks in accordance with the foregoing will help to further improve driving stability during the shift between driving along a straight course and driving along a bend, and vice versa.

[0078] Preferably, said first width is less than 28 mm.

[0079] Preferably, said first width is greater than 26 mm.

[0080] In preferred embodiments, said first width is comprised between 26 mm and 28 mm.

[0081] Preferably, said second width is greater than 24 mm.

[0082] Preferably, said second width is less than 26 mm.

[0083] In preferred embodiments, said second width is comprised between 24 mm and 26 mm.

[0084] Preferably, said maximum chord is greater than 80 mm.

[0085] Preferably, said maximum chord is less than 150 mm.

[0086] In preferred embodiments, said maximum chord is comprised between 80 mm and 150 mm.

[0087] Preferably, each first lateral block is arranged at a first axial distance from a respective central block such that the ratio between said first axial distance and said second width is comprised between 0.4 and 0.6.

[0088] Preferably, each second lateral block is arranged at a first axial distance from a respective central block such that the ratio between said first axial distance and said second width is comprised between 0.4 and 0.6. The Applicant believes that sizing the central and lateral blocks in accordance with the foregoing will help to further improve driving stability during the shift between driving along a straight course and driving along a bend, and vice versa.

[0089] Preferably, the ratio between said first axial distance and said first width is greater than 0.31.

[0090] Preferably, the ratio between said first axial distance and said first width is less than 0.48.

[0091] In preferred embodiments, the ratio between said first axial distance and said first width is comprised between 0.31 and 0.48.

[0092] Preferably, said first axial distance is greater than 9 mm.

[0093] Preferably, said first axial distance is less than 13 mm.

[0094] In preferred embodiments, this first axial distance is comprised between 9 mm and 13 mm.

[0095] Preferably, said tread band has a predetermined circumferential extension.

[0096] Preferably, said central blocks have a maximum length in the circumferential direction.

[0097] Preferably, the ratio between said maximum length and said circumferential extension is less than 0.078.

[0098] Preferably, the ratio between said maximum length and said circumferential extension is greater than 0.065.

[0099] In preferred embodiments, the ratio between said maximum length and said circumferential extension is comprised between 0.065 and 0.078.

[0100] Preferably, said maximum length is less than 17 mm.

[0101] Preferably, said maximum length is greater than 15 mm.

[0102] In preferred embodiments, said maximum length is comprised between 15 mm and 17 mm.

[0103] In some preferred embodiments, said first lateral blocks have a maximum length in the circumferential direction equal to that of the central blocks.

[0104] In some preferred embodiments, said second lateral blocks have a maximum length in the circumferential direction equal to that of the central blocks.

[0105] In some preferred embodiments, each first lateral block is aligned in the axial direction to a respective central block.

[0106] In some preferred embodiments, each second lateral block is aligned in the axial direction to a respective central block.

[0107] In other preferred embodiments, each first lateral block is misaligned in the axial direction with respect to a respective central block.

[0108] In other preferred embodiments, each second lateral block is misaligned in the axial direction with respect to a respective central block.

[0109] Preferably, each central block is arranged at a predetermined minimum circumferential distance from a circumferentially consecutive central block.

[0110] Preferably, the ratio between said minimum circumferential distance and said maximum length is greater than 2.4.

[0111] Preferably, the ratio between said predetermined minimum circumferential distance and said maximum length is less than 2.8.

[0112] In preferred embodiments, the ratio between said minimum circumferential distance and said maximum length is comprised between 2.4 and 2.8.

[0113] Preferably, said predetermined minimum circumferential distance is greater than 41 mm.

[0114] Preferably, said predetermined minimum circumferential distance is shorter than 44 mm.

[0115] Preferably, said predetermined minimum circumferential distance is comprised between 41 mm and 44 mm.

[0116] Preferably, each first lateral block is arranged at a minimum circumferential distance from a first consecutive circumferential block equal to the predetermined minimum circumferential distance.

[0117] Preferably, each second lateral block is arranged at a minimum circumferential distance from a second consecutive circumferential block equal to said predetermined minimum circumferential distance.

[0118] Preferably, each of said central blocks is delimited by a first longitudinal face and a second longitudinal face opposite to the first longitudinal face.

[0119] The first longitudinal face and the second longitudinal face, therefore, delimit a central block from opposite sides along an axial direction.

[0120] Preferably, each of said first lateral blocks and / or said second lateral blocks is delimited by a respective axially inner face and a respective axially outer face opposite to the axially inner face.

[0121] The axially inner and axially outer faces therefore delimit a first lateral block and a second lateral block on opposite sides along an axial direction.

[0122] Preferably, each of said central blocks and / or said first lateral blocks and / or said second lateral blocks is delimited by a first transversal face and a second transversal face opposite to the first transversal face.

[0123] The first transversal face and the second transversal face, therefore, delimit a block on opposite sides along the circumferential direction.

[0124] In some preferred embodiments, at least one of the first longitudinal face, the second longitudinal face, the axially inner face, the axially outer face, the first transversal face and the second transversal face is flat.

[0125] In other preferred embodiments, at least one of the first longitudinal face, the second longitudinal face, the axially inner face, the axially outer face, the first transversal face and the second transversal face is concave towards the inside of the respective block.

[0126] The Applicant observed that the provision of concave faces towards the inside of the block allows, on the one hand, to locally increase the distance between adjacent portions of blocks in the axial and / or circumferential direction, to the benefit of penetrability of the blocks into the terrain, and, on the other hand, facilitates the compaction of the terrain next to those faces, to the benefit of driving stability.

[0127] In some preferred embodiments, the first transversal face of the central blocks and / or first lateral blocks and / or second lateral blocks is substantially perpendicular to the equatorial plane.

[0128] In other preferred embodiments, the first transversal face of the central blocks and / or first lateral blocks and / or second lateral blocks comprises a first wall extending between an axially inner edge of said first transversal face and a central portion of said first transversal face.

[0129] Preferably, said first wall is inclined with respect to said equatorial plane by a first angle.

[0130] Preferably, the first transversal face of the central blocks and / or first lateral blocks and / or second lateral blocks comprises a second wall extending between an axially outer edge of said first transversal face and said central portion of said first transversal face.

[0131] Preferably, said second wall is inclined with respect to said equatorial plane on the opposite side with respect to said first wall by a second angle.

[0132] Preferably, the first wall and the second wall of the central blocks join to each other at a first joining line defined in said central portion of the first transversal face of the central blocks.

[0133] Preferably, said first joining line has a circumferential distance from the circumferentially closest central block greater than that of the axially inner edge and of the axially outer edge of said first transversal face. Preferably, said first joining line is arranged at a distance from the circumferentially closest central block such that the ratio between said distance and said circumferential extension is greater than 0.019.

[0134] Preferably, said first joining line is arranged at a distance from the circumferentially closest central block such that the ratio between said distance and said circumferential extension is shorter than 0.021.

[0135] In preferred embodiments, said first joining line is arranged at a distance from the circumferentially closest central block such that the ratio between said distance and said circumferential extension is comprised between 0.019 and 0.021.

[0136] Preferably, said first joining line is arranged at a distance from the circumferentially closest central block greater than 42 mm.

[0137] Preferably, said first joining line is arranged at a distance from the circumferentially closest central block shorter than 46 mm.

[0138] In preferred embodiments, said first joining line is arranged at a distance from the circumferentially closest central block comprised between 42 mm and 46 mm, preferably between 42.7 mm and 45 mm.

[0139] Preferably, said first joining line is arranged on said equatorial plane.

[0140] Preferably, said first angle is greater than 45°, more preferably greater than 55°, even more preferably greater than 65°, even more preferably greater than 75°.

[0141] Preferably, said first angle is less than 89°, more preferably less than 88°, even more preferably less than 87°, even more preferably greater than 86°.

[0142] In preferred embodiments, said first angle is comprised between 45° and 89°, preferably between 55° and 88°, more preferably between 65° and 87°, even more preferably between 75° and 86°, e.g. equal to 85°.

[0143] Preferably, said second angle is greater than 45°, more preferably greater than 55°, even more preferably greater than 65°, even more preferably greater than 75°.

[0144] Preferably, said second angle is less than 89°, more preferably less than 88°, even more preferably less than 87°, even more preferably less than 86°.

[0145] In preferred embodiments, said second angle is comprised between 45° and 89°, preferably between 55° and 88°, more preferably between 65° and 87°, even more preferably between 75° and 86°, e.g. equal to 85°.

[0146] In particularly preferred embodiments, said first angle is equal to said second angle.

[0147] In some preferred embodiments, the first transversal face of the first and / or second lateral blocks is substantially perpendicular to the equatorial plane.

[0148] In other preferred embodiments, the first transversal face of the first and / or second lateral blocks is inclined with respect to the equatorial plane by an angle comprised between 75° and 90°.

[0149] In this case, the first transversal face of each pair of lateral blocks that are axially opposite to a central block forms, with the first transversal face of said central block, a sort of curved surface that contributes to compacting the terrain between circumferentially adjacent blocks, to the benefit of off-road performance, especially in the case of soft and thus non-compact terrain.

[0150] In further preferred embodiments, the first transversal face of the first lateral blocks and / or second lateral blocks comprises a respective first wall extending between an axially inner edge of said respective first transversal face and a respective central portion of said respective first transversal face.

[0151] Preferably, said respective first wall is inclined with respect to a reference plane parallel to said equatorial plane by a respective angle. Preferably, said respective angle is equal to said first angle.

[0152] Preferably, the first transversal face of the first lateral blocks and / or second lateral blocks comprises a respective second wall extending between an axially outer edge of said respective first transversal face and said respective central portion of said first transversal face.

[0153] Preferably, said respective second wall is inclined with respect to said reference plane on the opposite side with respect to said respective first wall by a respective second angle.

[0154] Preferably, said respective second angle is equal to said first angle.

[0155] Preferably, said respective first and second angles have the same value as the inclination angles of the first and second walls of the first transversal face of the central blocks.

[0156] Preferably, said respective first wall and respective second wall of said first lateral blocks and / or second lateral blocks join to each other at a second joining line defined in said respective central portion of said respective first transversal face.

[0157] Preferably, said second joining line has a circumferential distance from the circumferentially closest lateral block greater than that of the axially inner edge and axially outer edge of said respective first transversal face.

[0158] In some preferred embodiments, the first transversal face and the second transversal face of the central blocks, the first lateral blocks and the second lateral blocks are perpendicular to the equatorial plane.

[0159] In other preferred embodiments, the first transversal face of the central blocks, the first lateral blocks and the second lateral blocks are perpendicular to the equatorial plane, while the second transversal face of the central blocks comprises said first joining line and the second transversal face of the first lateral blocks and of the second lateral blocks comprises said second joining line. In further preferred embodiments, the first transversal face and the second transversal face of the central blocks are perpendicular to the equatorial plane and the first transversal face and the second transversal face of the first lateral blocks and second lateral blocks are inclined with respect to the equatorial plane by an angle between 75° and 90°.

[0160] In some preferred embodiments, said respective axially outer face is parallel to the equatorial plane.

[0161] In some preferred embodiments, the respective second transversal face is perpendicular to the equatorial plane.

[0162] Preferably, each of said first lateral blocks and second lateral blocks comprises an upper portion tapered outwards at a connecting edge between said respective axially outer face and said respective second transversal face.

[0163] This arrangement makes it possible to reduce the top surface area of the lateral blocks, to the benefit of their penetrability into the terrain, without at the same time penalising the robustness of these blocks, and therefore their ability to bear the stresses (mainly torsional but also bending) to which they are subjected during tyre rolling whenever they enter the footprint area.

[0164] In other preferred embodiments, said respective axially outer face is inclined with respect to a plane parallel to the equatorial plane by an angle greater than 10°.

[0165] Preferably, said axially outer face is inclined with respect to a plane parallel to the equatorial plane by an angle of less than 45°.

[0166] In preferred embodiments, the respective axially outer face is inclined with respect to a plane parallel to the equatorial plane by an angle comprised between 10° and 45°.

[0167] Preferably, at least some of the central blocks comprise a respective recess extending along a circumferential direction at a centre line plane of the respective block and having a depth less than that of the respective block.

[0168] Preferably, at least some of the first lateral blocks comprise a respective recess extending along a circumferential direction at a centre line plane of the respective block and having a depth less than that of the respective block.

[0169] Preferably, at least some of the second lateral blocks comprise a respective recess extending along a circumferential direction at a centre line plane of the respective block and having a depth less than that of the respective block.

[0170] Preferably, said depth is less than or equal to one third of the depth of the respective block.

[0171] Preferably, each shoulder annular portion comprises a plurality of circumferentially consecutive shoulder blocks.

[0172] Preferably, said shoulder blocks are misaligned in the axial direction with respect to said central blocks.

[0173] Preferably, said shoulder blocks are misaligned in the axial direction with respect to said first lateral blocks.

[0174] Preferably, said shoulder blocks are misaligned in the axial direction with respect to said second lateral blocks.

[0175] Preferably, each of said shoulder blocks has an axially inner face which is concave towards the inside of the block.

[0176] In some embodiments, each of said shoulder blocks comprises a recess.

[0177] Preferably, the tread band has a void to solid ratio greater than 0.75.

[0178] Preferably, the tread band has a void to solid ratio less than 0.96.

[0179] In preferred embodiments, the tread band has a void to solid ratio comprised between 0.75 and 0.96.

[0180] The Applicant found that the aforementioned void to solid ratio values maximise the tyre off-road performance in medium-soft terrain. Preferably, a plurality of blocks formed of a central block, a first lateral block axially adjacent to the central block, a second lateral block axially adjacent to the central block, and possibly a first shoulder block adjacent to the first lateral block and a second shoulder block adjacent to the second lateral block, belongs to, and defines, a module that is repeated along the entire circumferential extension of the tread band.

[0181] Preferably, said tyre has a fitting diameter comprised between 10 inches and 19 inches.

[0182] Preferably, said tyre is a rear tyre.

[0183] DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0184] Further characteristics and advantages of the tyre of the present invention will become clearer from the following detailed description of preferred embodiments thereof, made with reference to the appended drawings. In such drawings:

[0185] - Figure 1 is a schematic view of a radial section of a motorcycle tyre according to the present invention;

[0186] - Figure 2 is a schematic perspective view of a first preferred embodiment of a rear tyre according to the present invention;

[0187] - Figure 3 is a schematic front view of a portion of the tyre of Figure 2;

[0188] - Figure 4 shows the plan extension of an enlargement of a circumferential section of the portion of Figure 3;

[0189] - Figure 5 schematically shows an enlargement of a central block shown in the previous figures and its relative position with respect to a similar circumferentially adjacent central block;

[0190] - Figure 6 schematically shows an enlargement of a lateral block shown in the previous figures and its relative position with respect to a similar circumferentially adjacent lateral block;

[0191] - Figure 7 shows the plan extension of an enlargement of a circumferential section of a second embodiment of a rear tyre according to the present invention;

[0192] - Figure 8 shows the plan extension of an enlargement of a circumferential section of a further embodiment of a rear tyre according to the present invention.

[0193] With reference to Figures 1 and 2, a tyre for motorcycles having a high weight and medium-large piston displacement, so-called "off-road" or of the "Motocross" type, according to a preferred embodiment of the present invention, is indicated with 1.

[0194] Tyre 1 is a rear tyre, i.e. it is intended to be mounted on the rear wheel of the aforementioned motorcycles.

[0195] An equatorial plane X-X and a rotation axis R are defined in the tyre 1 (Figure 2). A circumferential direction arranged according to the direction of rotation W of the tyre 1 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 R are also defined.

[0196] The tyre 1 comprises a carcass structure 2 formed by at least two carcass plies 3 radially overlapping each other and each consisting of a sheet of elastomeric material incorporating a plurality of reinforcing cords made of fibrous textile material, not shown.

[0197] The reinforcing cords are essentially parallel to each other in each carcass ply 3 and are oriented according to directions inclined with respect to the equatorial plane X-X of the tyre 1 in each carcass ply 3 and according to opposite directions with respect to the cords of the radially adjacent carcass ply 3 (carcass with crossed plies).

[0198] The carcass structure 2 is typically coated, on the inner walls thereof, by a sealing layer 100, or so-called "liner", essentially consisting of an airtight layer of elastomeric material, adapted to ensure the hermetic seal of the tyre itself 1 once inflated.

[0199] Each carcass ply 3 is shaped according to a substantially toroidal configuration. At least some of the carcass plies 3 have their axially opposite lateral edges 3a turned-up to respective annular reinforcing structures 4 intended to hold the tyre 1 on a corresponding mounting rim (not shown). The annular reinforcing structures 4 are typically called "bead cores".

[0200] In order to increase the structural homogeneity of the tyre 1, the carcass plies 3 have an axial extension different from each other.

[0201] A tapered elastomeric filler 5 is applied on the outer perimetral edge of the bead cores 4. The elastomeric filler 5 occupies the space defined between the respective carcass ply 3 and the corresponding turned-up lateral edge 3a of the carcass ply 3.

[0202] The area of the tyre 1 comprising the bead core 4 and the elastomeric filler 5 forms the so-called bead 9, which is intended to anchor the tyre 1 on the rim, not shown.

[0203] In one embodiment thereof, each carcass ply 3 is made by arranging side by side a plurality of strips of elastomeric material reinforced by the aforementioned cords.

[0204] A belt structure 6 is applied on the carcass structure 2, in a radially outer position thereof. The belt structure 6 comprises at least one belt layer 6a typically formed from rubber-coated textile or metallic reinforcing cords.

[0205] Preferably, the belt structure 6 is of the zero degrees type, i.e. the belt layer 6a is made through reinforcing cords arranged substantially parallel and side-by-side to form a plurality of turns. Such turns are substantially oriented according to the circumferential direction (typically with an angle comprised between 0° and 5°), such a direction usually being called "zero degrees" with reference to how it lies with respect to the circumferential direction of the tyre 1.

[0206] Preferably, the typically called "zero degrees" belt layer 6a can comprise windings arranged axially side-by-side of a single reinforcing cord or of a rubber-coated textile band which comprises reinforcing cords arranged axially side-by-side.

[0207] The reinforcing cords of the zero degrees belt layer 6a are typically metal cords. They are made of steel wires having high carbon content, i.e. steel wires with a carbon content of at least 0.6 - 0.7%. Preferably such metal reinforcing cords are high elongation (HE) cords.

[0208] In order to improve adhesion between the belt structure 6 and the carcass structure 2, an adhesion layer 7 made of elastomeric material is provided between the aforementioned two structures. Such an adhesion layer preferably extends over a surface substantially corresponding to the extension surface of the belt structure 6.

[0209] Alternatively, the adhesion layer 6 extends over a surface larger than the extension surface of the belt structure 6.

[0210] In a preferred embodiment, the adhesion layer 6 comprises short aramid fibres, e.g. Kevlar®, dispersed in said elastomeric material.

[0211] A tread band 8 is provided in a radially outer position with respect to the belt structure 6. The tread band 8 is made of an elastomeric material and, following a moulding operation carried out in conjunction with a vulcanisation step of the tyre 1, a plurality of blocks are typically obtained on the tread band 8, the blocks being separated from each other by longitudinal and / or transversal cavities or grooves to define a desired tread pattern.

[0212] The composition of the tread band 8 is such that the tread band 8 has only one compound on its radially outer surface.

[0213] In one embodiment, the tread band 8 is made in a cap-and-base mode and comprises a radially outer portion overlapped to an elastomeric substrate (not shown in Figure 1). The substrate is overlapped on the belt structure 6 and preferably extends over a surface substantially corresponding to the extension area of the radially outer portion of the tread band 8. Alternatively, said substrate extends only over a portion of the radially outer extension of the tread band 8, for example over opposite lateral portions of the tread band 8.

[0214] The tyre 1 further comprises a pair of sidewalls 10 applied laterally on opposite sides with respect to said carcass structure 2.

[0215] 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.

[0216] The tyre 1 also has a maximum chord "C", defined 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 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 can be formed with a joining line.

[0217] The tyre 1 has a "curvature ratio" f / C, defined by the ratio between the arrow "f" and the aforementioned maximum chord "C", less than or equal to approximately 0.33, relatively high sidewalls and not particularly high curvature.

[0218] Preferably, the tyre 1 has a maximum chord C comprised between 80 mm and 150 mm and is intended to be mounted on wheel rims with fitting diameters comprised between 10 inches and 19 inches.

[0219] In the tyre 1, the sidewall height ratio (H-f) / H is equal to at least about 0.5.

[0220] Preferably, the tyre 1 has a fitting diameter comprised between 10 inches and 19 inches.

[0221] As shown in the figures, the tyre 1 is of the tread block type, i.e. the tread band 8 comprises a base surface 8a (Figures 1-3) from which a plurality of central blocks 15, arranged along a respective circumferential row 15*, and lateral blocks 20, 60, arranged along respective circumferential rows 20*, 60*, protrude. The aforementioned blocks are defined by a plurality of longitudinal grooves 25 (Figure 1) and transversal grooves 26 (Figure 2).

[0222] The tread band 8 further comprises a plurality of shoulder blocks 30, 70 arranged along respective circumferential rows 30*, 70* and separated by transversal shoulder grooves 27.

[0223] The tread blocks 15, 20, 60, 30, 70 and grooves 25, 26 and 27 define a tread pattern with a void to solid ratio comprised between 0.75 and 0.96.

[0224] As shown in the figures, the tread band 8 is symmetrical with respect to the equatorial plane X-X.

[0225] The blocks of the embodiment of the tyre shown in Figure 2 are described hereinafter with reference to Figures 3-6.

[0226] Figure 3 shows a portion of the tread band 8 of the tyre 1 of Figure 2 in a frontal view, while Figure 4 shows an enlargement of the portion of Figure 3, Figure 5 shows an enlargement of a central part of the portion of Figure 3 and Figure 6 shows an enlargement of a lateral part of the portion of Figure 3.

[0227] In particular, Figure 4 shows a module T of pitch P that repeats circumferentially along the entire circumferential extension of the tyre 1.

[0228] Some particularly interesting dimensions are also shown in Figures 4-6. Please note that Figures 2-6 are schematic drawings that do not necessarily reflect the exact distances between the various blocks and the mutual arrangement of the blocks.

[0229] With reference to Figure 3, the tread band 8 comprises a central annular portion M extending astride of the equatorial plane X-X and two shoulder annular portions S arranged on opposite sides with respect to the central annular portion M.

[0230] The central annular portion M comprises a circumferential row 15* of circumferentially consecutive central blocks 15 arranged astride of the equatorial plane X-X and aligned with each other in the circumferential direction. The central annular portion M further comprises a first circumferential row 20* of circumferentially consecutive first lateral blocks 20 arranged next to the circumferential row 15* and aligned with each other in the circumferential direction and a second circumferential row 60* of circumferentially consecutive second lateral blocks 60 arranged next to the circumferential row 15* on the opposite side with respect to the first circumferential row 20* and aligned with each other.

[0231] Each first lateral block 20 and second lateral block 60 is axially adjacent to a respective central block 15. In particular, each first lateral block 20 and second lateral block 60 is aligned in the axial direction to a respective central block 15.

[0232] Each of the two shoulder annular portions S comprises a respective circumferential row 30*, 70* of lateral blocks 30, 70 that are circumferentially consecutive and aligned to each other in the circumferential direction.

[0233] The shoulder blocks 30, 70 are misaligned in the axial direction with respect to the lateral blocks 20, 60 and central blocks 15.

[0234] As shown in Figure 4, in a module T of pitch P there are a central block 15, the first lateral block 20 adjacent to the aforementioned central block 15, the second lateral block 60 adjacent to the aforementioned central block 15, a shoulder block 30 adjacent to the aforementioned lateral block 20, the shoulder block 70 adjacent to the aforementioned lateral block 60 and aligned in the axial direction to the aforementioned shoulder block 30.

[0235] Preferably, the tyre 1 is defined by a plurality of modules T as described above, which are repeated as such along the entire circumferential extension of the tread band 8. However, alternative embodiments are foreseen in which the aforementioned modules T are repeated as such only over a circumferential section of the tyre 1 of not less than 85% of the circumferential extension of the tread band 8. Details on the shape and relative position of the central blocks 15, lateral blocks 20, 60 and shoulder blocks 30, 70 are given below. This description will be made with reference to Figures 3-6. For ease of reading, although reference will be made to both the first lateral blocks 20, and their relative position with respect also to the central blocks 15 and the shoulder blocks 30, and the second lateral blocks 60, and their relative position with respect to the central blocks 15 and the shoulder blocks 70, in Figure 6 the numerical references and dimensions will only be associated with the first lateral blocks 20, it being understood that these numerical references and dimensions are also intended to be associated with the second lateral blocks 60.

[0236] As shown in Figure 4, the central blocks 15 have a first width LI in the axial direction and a maximum length 11 in the circumferential direction.

[0237] Similarly, the first lateral blocks 20 and the second lateral blocks 60 have a second width L2 in the axial direction and a length in the circumferential direction equal to 11.

[0238] The ratio between the second width L2 and the first width LI is comprised between 0.65 and 1.3, preferably between 0.7 and 1.2.

[0239] The ratio between the first width LI and the maximum chord C is comprised between 0.15 and 0.25.

[0240] The ratio between the second width L2 and the maximum chord C is comprised between 0.19 and 0.21.

[0241] The first width LI is comprised between 26 mm and 28 mm.

[0242] The second width L2 is comprised between 24 mm and 26 mm.

[0243] The maximum length 11 is comprised between 15 mm and 17 mm.

[0244] Each first lateral block 20 and second lateral block 60 is arranged at an axial distance DI from a respective central block 15 such that the ratio between said axial distance DI and the second width L2 is comprised between 0.4 and 0.6, e.g. equal to 0.5. The ratio between the axial distance D1 and the first width LI is comprised between 0.31 and 0.48.

[0245] The axial distance D1 is comprised between 9 mm and 13 mm.

[0246] The ratio between the maximum length 11 and the circumferential extension of the tread band 8 is comprised between 0.065 and 0.078.

[0247] As shown in Figure 5, each central block 15 is arranged at a minimum circumferential distance del from a circumferentially consecutive central block 15 comprised between 41 mm and 44 mm.

[0248] The ratio between said minimum circumferential distance del and the maximum length 11 is comprised between 2.4 and 2.8.

[0249] Similarly, as shown in Figure 6, each first lateral block 20 and second lateral block 60 is arranged at a minimum circumferential distance de2 from a circumferentially consecutive first lateral block 20 and second lateral block 60, respectively, comprised between 41 mm and 44 mm, preferably equal to del.

[0250] As shown in Figure 5, each central block 15 is delimited by a first longitudinal face 15a, a second longitudinal face 15b opposite to the first longitudinal face 15a, a first transversal face 15c and a second transversal face 15d opposite to the first transversal face 15c.

[0251] Similarly, as shown in Figure 6, each first lateral block 20 and second lateral block 60 is delimited by an axially inner face 20a, an axially outer face 20b opposite to the axially inner face 20a, a first transversal face 15c and a second transversal face 15d opposite to the first transversal face 15c.

[0252] The first longitudinal face 15a and the second longitudinal face, of the central blocks 15 of 15b, as well as the axially inner face 20a and axially outer face 20b of the first lateral blocks 20 and of the second lateral blocks 60 are all flat and parallel to the equatorial plane X-X.

[0253] The second transversal face 15d of the central blocks 15 and the second transversal face 20d of the first lateral blocks 20 and of the second lateral blocks 60 are all flat and perpendicular to the equatorial plane X- X.

[0254] Differently, as shown in Figures 5 and 6, the first transversal face 15a of the central blocks 15 and the first transversal face 20a of the first lateral blocks 20 and of the second lateral blocks 60 are concave, with the concavity facing toward the inside of the block.

[0255] In particular, as shown in Figure 5, the axially inner face 15a of the central blocks 15 comprises a first wall 150a extending between a first edge 150 of the first transversal face 15c and a central portion 155 of the first transversal face 15c and a second wall 160a extending between an opposite edge 160 of the first transversal face 15c and the aforementioned central portion 155.

[0256] The first edge 150 and the second edge 160 of the first transversal face 15c have the same minimum circumferential distance from the circumferentially adjacent central block 15.

[0257] The first wall 150a and the second wall 160a are inclined on opposite sides with respect to the equatorial plane X-X by a first angle al and a second angle a2, respectively, preferably equal to al. The angles al and a2 are preferably comprised between 45° and 89°, more preferably between 55° and 88°, more preferably between 65° and 87°, even more preferably between 75° and 86°, e.g. 85°.

[0258] The first wall 150a and the second wall 160a join to each other at a first joining line VI defined in the central portion 155 of the first transversal face 15c, in particular arranged in the equatorial plane X-X, and having a distance dvl from the second transversal face 15d of the circumferentially adjacent block greater than del.

[0259] Preferably, the distance dvl is comprised between 42 mm and 46 mm, more preferably between 42.7 mm and 45 mm.

[0260] Preferably, the ratio between said distance dvl and the circumferential extension of the tread band 8 is comprised between 0.019 and 0.021.

[0261] Similarly, as shown in Figure 6, the axially inner face 20a of the first lateral blocks 20 and of the second lateral blocks 60 comprises a first wall 250a extending between a first edge 250 of the first transversal face 20c and a central portion 255 of the first transversal face 20c and a second wall 260a extending between an opposite edge 260 of the first transversal face 20c and the aforementioned central portion 255.

[0262] The first edge 250 and the second edge 260 of the first transversal face 20c have the same distance from the first lateral block 20 or circumferentially adjacent second lateral block 60.

[0263] The first wall 250a and the second wall 260a are inclined on opposite sides with respect to a reference plane Pl parallel to the equatorial plane X-X by respective angles 01 and 02 preferably equal to al and a2.

[0264] The first wall 250a and the second wall 260a join to each other at a second joining line V2 defined in the central portion 255 of the first transversal face 20c and having a distance dv2 from the second transversal face 20d of the circumferentially adjacent block greater than de2 and preferably equal to dvl.

[0265] Still with reference to Figure 6, each of the first lateral blocks 20 and second lateral blocks 60 comprises an upper portion 40 tapered outwardly at a connecting edge 270 between the axially outer face 20b and the second transversal face 20d. The tapering is such that at the connecting edge 270 the height of the first lateral block 20 and of the second lateral block 60 is shorter than that at the line 41 defined on the radially outer face of the aforementioned blocks and from which the tapered upper portion 40 begins.

[0266] In view of the fact that the first transversal face 15c of the central blocks 15 and the first transversal face 20c of the first lateral blocks 20 and of the second lateral blocks 60 are not flat, in the tyre 1 described above:

[0267] - the maximum length 11 is measured in the circumferential direction between the first edge 150 or second edge 160 of a central block 15 (or between the first edge 250 and the second edge 260 of a first lateral block 20 or of a second lateral block 60) and the second transversal face 15d of the same central block 15 (or of the same first lateral block 20 or second lateral block 60);

[0268] - the minimum circumferential distance del (or de2) is measured in the circumferential direction between the first edge 150 or second edge 160 of a central block 15 (or between the first edge 250 and second edge 260 of a first lateral block 20 or of a second lateral block 60) and the second transversal face 20d of a circumferentially adjacent central block 15 (or of a circumferentially adjacent first lateral block 20 or second lateral block 60).

[0269] As shown in Figure 4, the shoulder blocks 30, 70 comprise respective axially inner faces 30a, 70a which are concave towards the inside of the block. As a result of this concavity, each shoulder block 30, 70 has, at its axially inner face 30a, 70a, opposite edges having a distance in the axial direction from the shoulder block 30, 70 axially aligned therewith, shorter than that of a central portion of that face interposed between said edges.

[0270] Figure 7 shows a portion of the tread band of an embodiment of the tyre of the present invention alternative to the one described above.

[0271] The tread band of the tyre of Figure 7 differs from that described with reference to Figures 2-6 only in that the first transversal faces 15c of the central blocks 15 and the first transversal faces 20c, 60c of the first lateral blocks 20 and second lateral blocks 60, respectively, are flat and perpendicular to the equatorial plane X-X. Furthermore, the first lateral blocks 20 and second lateral blocks 60 do not have the tapered upper portion 40 which is present in the first lateral blocks 20 and second lateral blocks 60 of the tyre 1 described above. Everything else is identical to what described above.

[0272] Figure 8 shows a portion of the tread band of an alternative embodiment of the tyre of the present invention.

[0273] The tread band of the tyre of Figure 8 differs from that described with reference to Figures 2-6 only in the elements described below.

[0274] The central blocks are identical to those described above with reference to Figure 7.

[0275] The first lateral blocks 20 and second lateral blocks 60 are misaligned in the axial direction with respect to the central blocks 20. In particular, the first transversal face 20c and the second transversal face 20d are inclined with respect to the equatorial plane X-X by respective angles preferably comprised between 75° and 90°.

[0276] In addition, the axially outer faces 20b of the first lateral blocks 20 and second lateral blocks 60 are inclined with respect to a plane parallel to the equatorial plane by an angle comprised between 10° and 45°, e.g. 25°.

[0277] Furthermore, the first lateral blocks 20 and second lateral blocks 60 do not have the tapered upper portion 40 which is present in the first lateral blocks 20 and second lateral blocks 60 of the tyre 1 described above. Everything else is identical to what described above.

[0278] Finally, the shoulder blocks 30, 70 have a shape slightly different from the one of the shoulder blocks of the tyre 1 described with reference to Figures 2-6, although they still have concave axially inner faces 30a, 70a. In this case, the shoulder blocks 30, 70 each have a respective recess 31, 71 on their respective radially outer surface.

[0279] In all the embodiments described above, any central block 15 and / or first lateral block 20 and / or second lateral block 60 described above and shown in the Figures 2-8 may further comprise a respective recess extending in a circumferential direction at a centre line plane of the block (i.e. astride of the equatorial plane for central blocks 15 and astride of the plane Pl for first lateral blocks 20 and second lateral blocks 60 described with reference to Figures 2-8). This recess, indicated by 50 and shown for ease of reading only at some of the blocks shown in Figure 7, has a depth less than that of the respective block. This depth is preferably less than or equal to one third of the depth of the respective block.

[0280] The recess 50 may not be provided in the blocks of the tread band of the embodiment of Figure 7 or may also be provided in the blocks of the tread band of all the other embodiments described above. In addition, this recess 50 can only be provided in central blocks 15 (or only in some of them) and not also in the first lateral blocks 20 and second lateral blocks 60, or vice versa.

[0281] COMPARATIVE TESTS

[0282] The Applicant has made a sample of a front tyre 1 in accordance with an embodiment of the present invention and in particular having the tread pattern shown in Figure 2. Such a tyre is indicated hereinafter with INV.

[0283] The tyre INV had structure and dimensions identical to those of a rear tyre of the Applicant for motorcycles intended for off-road use and currently sold on the market. Such a tyre is indicated hereinafter with Ref.

[0284] Outdoor comparison tests were carried out with the tyre Ref, the latter being appreciated by customers for its excellent off-road behaviour.

[0285] The tests were carried out by mounting both the tyres (inflated with the same inflation pressure) on the rear wheel of a Honda CRF 450 motorcycle, with an identical tyre mounted on the front wheel and in substantially identical environmental conditions.

[0286] The rear tyres INV and Ref had the following size: 110 / 90-19. The front tyre had the following size: 80 / 100-21. The behaviour of the two tyres INV and Ref on the same off-road track, on both medium-soft and hard and compact terrain, was evaluated and the driver was asked to make a comparative judgement. In particular, driving stability was assessed during the shift between driving along a straight course and driving along a bend, and vice versa.

[0287] The driver judged the performance achieved with the tyre INV to be better on both medium-soft and hard and compact terrain.

[0288] The Applicant thus had a confirmation confirm that the particular tread pattern adopted in the tyre of the invention effectively achieves the sought improvement in off-road performance in terms of driving stability in the shift between driving along a straight course and driving along a bend, not only on medium-soft terrain but also on hard and compact terrain.

[0289] Of course, a person skilled in the art can bring further modifications and changes to the tyre described above in order to satisfy specific and contingent application requirements, these modifications and changes being in any case within the scope of protection as defined by the following claims.

Claims

CLAIMS1. Off-road motorcycle tyre (1), comprising a tread band (8) having a central annular portion (M) extending astride of an equatorial plane (X-X) of the tyre (1) and two shoulder annular portions (S) arranged on opposite sides with respect to the central annular portion (M), wherein the central annular portion (M) comprises:- a plurality of circumferentially consecutive central blocks (15) arranged astride of the equatorial plane (X-X) and having a first width (LI) in the axial direction;- a plurality of circumferentially consecutive first lateral blocks (20) arranged next to the central blocks (15) and having a second width (L2) in the axial direction;- a plurality of circumferentially consecutive second lateral blocks (60) arranged next to the central blocks (15) on the opposite side with respect to said plurality of first lateral blocks (20) and having said second width (L2) in the axial direction; wherein the ratio between said second width (L2) and said first width (LI) is comprised between 0.65 and 1.3.

2. Off-road motorcycle tyre (1) according to claim 1, wherein said tread band (8) has a maximum chord (C) and wherein the ratio between said first width (LI) and said maximum chord (C) is less than 0.25 and the ratio between said second width (L2) and said maximum chord (C) is greater than 0.19.

3. Off-road motorcycle tyre (1) according to claim 1, wherein said tread band (8) has a maximum chord (C) and wherein the ratio between said first width (LI) and said maximum chord (C) is greater than 0.15 and the ratio between said second width (L2) and said maximum chord (C) is less than 0.21.

4. Off-road motorcycle tyre (1) according to any one of the previous claims, wherein each first lateral block (20) and second lateralblock (60) is arranged at a first axial distance (DI) from a respective central block (15) and wherein the ratio between said first axial distance (DI) and said second width (L2) is comprised between 0.4 and 0.6.

5. Off-road motorcycle tyre (1) according to any one of the previous claims, wherein said tread band (8) has a predetermined circumferential extension and said central blocks (15) have a maximum length (11) in the circumferential direction, wherein the ratio between said maximum length (11) and said circumferential extension is less than 0.078.

6. Off-road motorcycle tyre (1) according to any one of the previous claims, wherein each of said central blocks (15) is delimited by a first longitudinal face (15a), a second longitudinal face (15b) opposite to the first longitudinal face (15a), a first transversal face (15c) and a second transversal face (15d) opposite to the first transversal face (15c), wherein at least one of the first longitudinal face (15a), the second longitudinal face (15b), the first transversal face (15c) and the second transversal face (15d) is flat or concave towards the inside of the respective block.

7. Off-road motorcycle tyre (1) according to claim 6, wherein said first transversal face (15c) is substantially perpendicular to the equatorial plane (X-X) or comprises:- a first wall (150a) extending between an axially inner edge (150) of said first transversal face (15c) and a central portion (155) of said first transversal face (15c) and inclined with respect to said equatorial plane (X-X);- a second wall (160a) extending between an axially outer edge (160) of said first transversal face (15c) and said central portion (155) of said first transversal face (15c) and inclined with respect to said equatorial plane (X-X) on the opposite side with respect to said first wall (150a);wherein said first wall (150a) and second wall (160a) join to each other at a first joining line (VI) defined in said central portion (155) of said first transversal face (15c) and having a circumferential distance (dvl) from the circumferentially closest central block (15) greater than the distance (del) of the axially inner edge (150) and of the axially outer edge (160) of said first transversal face (15c).

8. Off-road motorcycle tyre (1) according to any one of the previous claims, wherein each of said first lateral blocks (20) and second lateral blocks (60) is delimited by a respective axially inner face (20a), a respective axially outer face (20b) opposite to the respective axially inner face (20a), a respective first transversal face (20c) and a respective second transversal face (20d) opposite to the respective first transversal face (20c), wherein at least one of the respective axially inner face (20a), the respective axially outer face (20b), the respective first transversal face (20c) and the respective second transversal face (20d) is flat or concave towards the inside of the respective block.

9. Off-road motorcycle tyre (1) according to claim 8, wherein said respective first transversal face (20c) is substantially perpendicular to the equatorial plane (X-X) or is inclined with respect to the equatorial plane (X-X) by an angle comprised between 70° and 85° or comprises:- a respective first wall (250a) extending between an axially inner edge (250) of said respective first transversal face (20c) and a respective central portion (255) of said respective first transversal face (20c) and inclined with respect to a reference plane (Pl) parallel to said equatorial plane (X-X);- a respective second wall (260a) extending between an axially outer edge (260) of said respective first transversal face (20c) and said respective central portion (255) of said first transversal face (20c) and inclined with respect to said reference plane (Pl) on the opposite side with respect to said respective first wall (250a);wherein said respective first wall (250a) and respective second wall (260a) join to each other at a second joining line (V2) defined in said respective central portion (255) of said respective first transversal face (20c) and having a circumferential distance from the circumferentially closest lateral block (20, 60) greater than the distance (de2) of the axially inner edge (250) and of the axially outer edge (260) of said respective first transversal face (20c).

10. Off-road motorcycle tyre (1) according to claim 8 or 9, wherein:- said respective axially outer face (20b) is parallel to the equatorial plane (X-X);- said respective second transversal face (20d) is perpendicular to the equatorial plane (X-X); and wherein each of said first lateral blocks (20) and second lateral blocks (60) comprises, at a connecting edge (270) between said respective axially outer face (20b) and said respective second transversal face (20d), an upper portion (25) which is tapered outwardly.

11. Off-road motorcycle tyre (1) according to claim 8 or 9, wherein:- said respective axially outer face (20b) is inclined with respect to a plane parallel to the equatorial plane (X-X) by an angle comprised between 10° and 45°;- said respective second transversal face (20d) is inclined with respect to the equatorial plane (X-X) by an angle comprised between 70° and 90°.

12. Off-road motorcycle tyre (1) according to any one of the previous claims, wherein said tread band (8) has a void to solid ratio comprised between 0.75 and 0.96.

13. Off-road motorcycle tyre (1) according to any one of the previous claims, wherein said tyre (1) has a fitting diameter comprisedbetween 10 inches and 19 inches and a maximum chord comprised between 80 mm and 150 mm.

14. Motorcycle tyre (1) according to any one of the previous claims, wherein said tyre (1) is a rear tyre.

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