Motorcycle tires and motorcycle tire pairs

Abstract

To provide a motorcycle tire capable of improving the handling performance and the grip performance.SOLUTION: The present invention discloses a motorcycle tire 1 of a bias structure. A tread portion 2 is provided with main grooves 8 and sipes 9. The main grooves 8 include first main grooves 11 extending from the crown region Cr to one side of a pair of shoulder regions Sh, and second main grooves 12 extending from the crown region Cr to the other side of the pair of shoulder regions Sh. The sipes 9 are formed only within the pair of shoulder regions Sh.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tire for a motorcycle and to a pair of tires for a motorcycle. [Background technology]

[0002] Patent Document 1 below describes a motorcycle tire having a tread portion. The tread portion is provided with main grooves having a groove width exceeding 2 mm and narrow grooves having a groove width of 2 mm or less. The main grooves and the narrow grooves are inclined with respect to the circumferential direction of the tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-104329 A Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, the tread of a motorcycle tire having a bias structure does not have a belt layer for exerting a hoop effect. In such motorcycle tires, the rubber thickness in the shoulder region of the tread is large, and the rigidity is high, so that the handling performance is likely to deteriorate. Note that the handling performance means the ease of handling operation to give a camber angle to the tire by tilting the body when turning a motorcycle.

[0005] On the other hand, providing a large number of grooves or sipes in the tread portion causes a problem of reduced grip performance.

[0006] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire for a motorcycle or the like that can improve handling performance and grip performance. [Means for solving the problem]

[0007] The present invention is a tire for motorcycles, comprising a tread portion having a pair of tread ends, and a carcass with a bias structure, the tread portion comprising, in a tread development view, a pair of shoulder regions each having an axial width of 30% of the tread development width axially inward from the pair of tread ends, and a crown region between the pair of shoulder regions, the tread portion being provided with a plurality of main grooves and a plurality of sipes, the main groove comprising a first main groove extending from the crown region to one side of the pair of shoulder regions, and a second main groove extending from the crown region to the other side of the pair of shoulder regions, the sipes being formed only in the pair of shoulder regions.

[0008] In the motorcycle tire according to the present invention, it is preferable that the maximum depth of the sipes is the same as the maximum depth of the main grooves.

[0009] In the motorcycle tire according to the present invention, it is desirable that one of the sipes and one of the main grooves are arranged adjacent to each other in the tire circumferential direction, that there is an overlapping portion in the tire axial direction, and that one of the sipes and one of the main grooves have the same depth on a first tire circumferential line passing through the overlapping portion.

[0010] In the motorcycle tire according to the present invention, it is preferable that the first main groove, the second main groove and the sipes are arranged so as not to communicate with each other.

[0011] In the motorcycle tire according to the present invention, it is preferable that each of the main grooves terminates without communicating with the tread end.

[0012] In the motorcycle tire according to the present invention, it is preferable that the main groove includes, in the shoulder region, a widened portion in which a groove width increases from an inner side toward an outer side in the tire axial direction.

[0013] In the motorcycle tire according to the present invention, it is preferable that the widened portion extends to an axially outer end of the main groove.

[0014] In the motorcycle tire according to the present invention, it is preferable that the sipe includes at least one raised portion that locally raises the bottom of the sipe.

[0015] In the motorcycle tire according to the present invention, it is preferable that the raised portion has an arc shape that is convex outward in the radial direction of the tire in a cross section along the sipe.

[0016] In the motorcycle tire according to the present invention, it is preferable that the sipes are offset axially outward from an axial middle position of the shoulder region.

[0017] The present invention relates to a pair of motorcycle tires, the front tire and the rear tire being the motorcycle tire described in any one of claims 1 to 10, and the rear tire has more sipes than the front tire.

[0018] In the pair of motorcycle tires according to the present invention, it is preferable that the tread portion of the rear tire has a land ratio of 80% or more.

[0019] In the pair of motorcycle tires according to the present invention, it is preferable that the tread portion of the rear tire has a land ratio of the crown region equal to or greater than a land ratio of the shoulder region.

[0020] In the pair of motorcycle tires according to the present invention, it is preferable that the tread portion of the front tire has a smaller land ratio than the tread portion of the rear tire.

[0021] In the pair of motorcycle tires according to the present invention, it is preferable that the tread portion of the front tire has a land ratio of the shoulder region that is equal to or greater than a land ratio of the crown region. Effect of the Invention

[0022] By adopting the above-mentioned configuration, the motorcycle tire of the present invention can improve handling performance and grip performance. [Brief description of the drawings]

[0023] [Figure 1] 1 is a development view of a tread portion showing one embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] FIG. 2 is an enlarged view of FIG. [Figure 4] FIG. 2 is an enlarged view of FIG. [Diagram 5] FIG. 2 is an enlarged view of FIG. [Figure 6] FIG. [Figure 7] FIG. 11 is a development view of a tread portion of another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a development view of a tread portion 2 of a motorcycle tire (hereinafter, sometimes simply referred to as a "tire") 1 of the present invention. The tire 1 of this embodiment is preferably used for on-road driving on dry asphalt roads, for example. However, the tire 1 of the present invention is not limited to such a usage mode.

[0025] Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. As shown in Fig. 2, in the tire 1, the contact surface 2a of the tread portion 2 is curved in a convex arc shape radially outward in order to obtain a sufficient contact area even during cornering with a large camber angle.

[0026] The tire 1 includes, for example, a carcass 6 that is bridged between the bead portions 4, 4, and a band layer 7 that is disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2.

[0027] The carcass 6 is made up of, for example, two carcass plies 6A and 6B arranged on the inside and outside in the tire radial direction. Each of the carcass plies 6A and 6B has a bias structure in which carcass cords (not shown) are arranged at an angle of 30 to 45 degrees with respect to the tire circumferential direction. Well-known materials are used for each of the carcass plies 6A and 6B.

[0028] The band layer 7 is made of one or more band plies 7A, in this embodiment, one band ply 7A, formed by spirally winding a band cord (not shown) at an angle of 5 degrees or less with respect to the tire circumferential direction. Well-known materials are used for the band ply 7A.

[0029] As shown in Fig. 1, the tread portion 2 has a pair of shoulder regions Sh each having an axial width Ws of 30% of the tread developed width TWe on the axially inner side of a pair of tread ends Te, Te, and a crown region Cr between the pair of shoulder regions Sh. The shoulder region Sh is a region where a large ground contact pressure acts mainly during cornering. The crown region Cr is a region where a large ground contact pressure acts mainly during straight running. In this specification, the tread developed width TWe is the axial distance between the tread ends Te, Te when the tread portion 2 is developed on a plane.

[0030] The tread portion 2 of this embodiment is provided with a plurality of main grooves 8 and a plurality of sipes 9. The tread portion 2 further includes, for example, a circumferential groove 10 extending in the tire circumferential direction. In this specification, the main groove 8 and the circumferential groove 10 are groove-like bodies with a maximum groove width exceeding 1.5 mm. In this specification, the sipes 9 are notch-like bodies with a maximum width of 1.5 mm or less. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured with the tire 1 in a normal state.

[0031] The "normal state" refers to a state in which the tire 1 is mounted on a normal rim (not shown), inflated to a normal internal pressure, and no load is applied.

[0032] The "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based, for example, "standard rim" in the case of JATMA, "Design Rim" in the case of TRA, and "Measuring Rim" in the case of ETRTO.

[0033] The "normal internal pressure" is the air pressure determined for each tire by each standard in the standard system including the standard on which the tire is based. In the case of JATMA, it is the "maximum air pressure." In the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." In the case of ETRTO, it is the "INFLATION PRESSURE."

[0034] The main groove 8 includes a first main groove 11 extending from the crown region Cr to one side (left side in the figure) of the pair of shoulder regions Sh, and a second main groove 12 extending from the crown region Cr to the other side (right side in the figure) of the pair of shoulder regions Sh. Such first main groove 11 and second main groove 12 can reduce the rigidity of the shoulder regions Sh on both sides of the tread portion 2 even when the rubber thickness of the shoulder regions Sh is formed to be large. Therefore, the tire 1 of this embodiment improves the contact with the road surface of the shoulder regions Sh during cornering, and thus improves handling performance.

[0035] The sipes 9 are formed only in a pair of shoulder regions Sh. This prevents the crown region Cr from being excessively degraded in stiffness, and thus provides excellent grip performance. The sipes 9 include a first sipe 9A arranged on one side of the shoulder region Sh and a second sipe 9B arranged on the other side of the shoulder region Sh.

[0036] The tread portion 2 of this embodiment is suitably used for the tread portion 2 of a tire for a front wheel of a motorcycle (not shown). The tread portion 2 shown in Fig. 1 can also be applied to the tread portion 2 of a tire for a rear wheel.

[0037] The first main groove 11, the second main groove 12 and the sipes 9 are arranged, for example, without communicating with each other. This makes it possible to suppress a large decrease in the rigidity of the tread portion 2.

[0038] In this embodiment, the main groove 8 further includes a third main groove 13, a fourth main groove 14, a fifth main groove 15, and a sixth main groove 16. In this embodiment, the third main groove 13 is adjacent to the first main groove 11 in the tire circumferential direction and is formed to have a shorter tire axial length than the first main groove 11. The third main groove 13 extends, for example, from the crown region Cr to the shoulder region Sh. The fourth main groove 14 is adjacent to the second main groove 12 in the tire circumferential direction and is formed to have a shorter tire axial length than the second main groove 12. The fourth main groove 14 extends from the crown region Cr to the other side of the shoulder region Sh. In this embodiment, the fifth main groove 15 is formed only on one side of the shoulder region Sh. In this embodiment, the sixth main groove 16 is formed only on the other side of the shoulder region Sh.

[0039] The first main groove 11 of this embodiment is symmetrical with the second main groove 12, which is offset in the tire circumferential direction, with the tire equator C in between. The third main groove 13 of this embodiment is symmetrical with the fourth main groove 14, which is offset in the tire circumferential direction, with the tire equator C in between. The fifth main groove 15 of this embodiment is symmetrical with the sixth main groove 16, which is offset in the tire circumferential direction, with the tire equator C in between. For this reason, in this specification, unless otherwise specified, the description of the first main groove 11, the third main groove 13, and the fifth main groove 15 also includes the description of the second main groove 12, the fourth main groove 14, and the sixth main groove 16.

[0040] Fig. 3 is an enlarged view of Fig. 1. As shown in Fig. 3, each of the main grooves 8 is inclined, for example, from the inside to the outside in the tire axial direction to one side (upper left in the figure) with respect to the tire circumferential direction. In this embodiment, the first main groove 11, the third main groove 13, and the fifth main groove 15 are inclined upward to the left. Such a main groove 8 exhibits high drainage performance because the flow of water in the groove becomes smooth. In this embodiment, the second main groove 12, the fourth main groove 14, and the sixth main groove 16 are inclined upward to the right (as shown in Fig. 1).

[0041] The main groove 8 includes, for example, in the shoulder region Sh, a widened portion 18 in which the groove width increases from the inside to the outside in the tire axial direction. Such widened portion 18 improves the contact of the shoulder region Sh with the road surface during cornering. The widened portion 18 is formed, for example, in the first main groove 11. In this embodiment, the widened portion 18 extends from the crown region Cr to the shoulder region Sh. The widened portion 18 refers to a state in which the ratio ((wb-wa) / La) of the difference (wb-wa) between the minimum groove width wa and the maximum groove width wb of each main groove 8 to its axial length La is 3% or more, and is distinguished from a constant width portion in which the ratio ((wb-wa) / La) is less than 3%.

[0042] Each of the main grooves 8 terminates without communicating with the tread end Te. This maintains high rigidity in the shoulder region Sh. The distance Li between the axially outer end 8e of the main groove 8 and the tread end Te is, for example, desirably 1 mm or more, and more desirably 2 mm or more. Furthermore, the distance Li is desirably, for example, 30% or less of the axial width Ws of the shoulder region Sh, and more desirably 25% or less. In this embodiment, the main grooves 8 and the sipes 9 terminate without communicating with the tread end Te.

[0043] The main groove 8 has a pair of groove edges 8s, 8t extending in the longitudinal direction. In this embodiment, one of the groove edges 8s is disposed axially inward of the other groove edge 8t.

[0044] Each of the main grooves 8 includes a first narrowed width portion 19 whose groove width decreases toward the inner end 8i in the tire axial direction, a second narrowed width portion 20 whose groove width decreases toward the outer end 8e in the tire axial direction, and a base portion 21 connecting the first narrowed width portion 19 and the second narrowed width portion 20. In this embodiment, the first narrowed width portion 19 includes the inner end 8i. In this embodiment, the second narrowed width portion 20 includes the outer end 8e. The base portion 21 includes a maximum width portion 21a that is the maximum groove width wb of the main groove 8. The first narrowed width portion 19 and the second narrowed width portion 20 maintain the rubber volume of the tread portion 2 large, suppressing excessive reduction in rigidity of the tread portion 2.

[0045] Each of the first reduced width portions 19 is formed, for example, by a portion in which one of a pair of groove edges 8s, 8t of the main groove 8 extends at a smaller angle with respect to the tire circumferential direction than the other of the groove edges 8s, 8t. In this embodiment, the groove edge 8s arranged on the inner side in the tire axial direction is formed so as to have a smaller angle with respect to the tire circumferential direction than the groove edge 8t arranged on the outer side in the tire axial direction. The first reduced width portion 19 is, for example, a portion in which the groove width narrows continuously from the base portion 21.

[0046] Although not particularly limited, when the tire 1 is specified to have a rotational direction N, it is desirable that one groove edge 8s be on the trailing side of the rotational direction N and the other groove edge 8t be on the leading side of the rotational direction N in order to improve grip performance and drainage performance.

[0047] The length Lc of the first narrowed width portion 19 of the first main groove 11 and the length Lc of the first narrowed width portion 19 of the third main groove 13 are preferably 5% or more, more preferably 10% or more, more preferably 30% or less, and even more preferably 25% or less of the width Wc (shown in FIG. 1) of the crown region Cr in the tire axial direction. The length Lc of the first narrowed width portion 19 of the fifth main groove 15 is preferably 3% or more, more preferably 5% or more, more preferably 17% or less, and even more preferably 15% or less of the width Ws (shown in FIG. 1) of the shoulder region Sh. This improves the handling performance and grip performance. The first narrowed width portion 19 also suppresses the occurrence of cracks at the bottom of the groove. The length Lc of the first narrowed width portion 19 is the length in the width center line direction.

[0048] Each of the second reduced width portions 20 is formed, for example, such that one (8s) of a pair of groove edges 8s, 8t includes an arc-shaped portion 22 that connects the base 21 and the second reduced width portion 20 with a smooth arc, and the other groove edge 8t has a crank-shaped portion 23 that is bent in a crank shape in a direction that reduces the groove width. Each of the second reduced width portions 20 is, for example, a portion where the groove width is sharply reduced compared to the base 21.

[0049] Although not particularly limited, the maximum groove width wc of each second reduced width portion 20 is preferably 15% or more of the maximum groove width wb of each main groove 8, more preferably 20% or more, more preferably 50% or less, and more preferably 40% or less. The axial length Ld of each second reduced width portion 20 is preferably 15% or more of the width Ws of the shoulder region Sh (shown in FIG. 1), more preferably 20% or more, more preferably 30% or less, and more preferably 25% or less. The maximum depth da of each second reduced width portion 20 is preferably 15% or more of the maximum depth D1 of each main groove 8 (shown in FIG. 2), more preferably 20% or more, more preferably 50% or less, and more preferably 40% or less. Such second reduced width portions 20 improve grip performance and handling performance, and suppress the occurrence of groove bottom cracks. The maximum depth D1 of each of the main grooves 8 is, for example, desirably 3.8 mm or more, more desirably 4.0 mm or more, desirably 8.0 mm or less, and more desirably 7.2 mm or less.

[0050] The first main groove 11 has, for example, a circumferential overlapping portion 25 that overlaps in the tire circumferential direction with a first main groove 11 adjacent thereto in the tire circumferential direction. Such a first main groove 11 further reduces the rigidity of the tread portion 2, improves contact with the road surface, and improves handling performance. The tire circumferential length Le of the circumferential overlapping portion 25 is preferably 5% or more of the tire circumferential length L1 of the first main groove 11, more preferably 8% or more, more preferably 15% or less, and even more preferably 12% or less.

[0051] Fig. 4 is an enlarged view of Fig. 1. As shown in Fig. 4, the third main groove 13 includes, for example, a constricted portion 26 where the groove width becomes smaller at the center side in the tire axial direction. The base 21 of the third main groove 13 includes, for example, the constricted portion 26, a first constant width portion 27 that joins the first reduced width portion 19 and the constricted portion 26 and has a constant width, and a second constant width portion 28 that joins the second reduced width portion 20 and the constricted portion 26 and has a constant width.

[0052] The constriction portion 26 is formed, for example, by an arc portion 31 in which one groove edge 8s extends in a convex arc shape toward the groove center line, and a crank-shaped portion 32 in which the other groove edge 8t extends in a crank shape in a direction that narrows the groove width.

[0053] FIG. 2 shows the constricted portion 26 of the fourth main groove 14. As shown in FIG. 2, the minimum depth dc of the constricted portion 26 is preferably 10% or more of the maximum depth D1 of the fourth main groove 14, more preferably 20% or more, more preferably 50% or less, and even more preferably 40% or less. The depth of the constricted portion 26 smoothly increases outward at both ends in the longitudinal direction. Also, as shown in FIG. 4, the minimum groove width wf of the constricted portion 26 is preferably 10% or more of the maximum groove width wb of the third main groove 13, more preferably 20% or more, more preferably 50% or less, and even more preferably 40% or less. Such a constricted portion 26 suppresses the occurrence of cracks at the groove bottom.

[0054] The fifth main groove 15 is formed, for example, to include a third constant width portion 35 that is disposed between the first reduced width portion 19 and the second reduced width portion 20 and has a constant width.

[0055] Fig. 5 is an enlarged view of Fig. 1. As shown in Fig. 5, the tire axial length LA of the first main groove 11 is preferably 30% or more of the tread developed width TWe, more preferably 35% or more, more preferably 50% or less, and more preferably 45% or less. The tire axial length LB of the third main groove 13 is preferably 25% or more of the tread developed width TWe, more preferably 30% or more, more preferably 45% or less, and more preferably 40% or less. The tire axial length LC of the fifth main groove 15 is preferably 25% or more of the tread developed width TWe, more preferably 30% or more, more preferably 45% or less, and more preferably 40% or less.

[0056] The sipes 9 are inclined, for example, from the inside to the outside in the tire axial direction to one side (upper left in the figure) with respect to the tire circumferential direction. The first sipes 9A are inclined in the same direction as the first main grooves 11. The second sipes 9B are inclined in the same direction as the second main grooves 12 (shown in FIG. 1).

[0057] Fig. 6 is a vertical cross-sectional view of the sipe 9. As shown in Fig. 6, the maximum depth de of the sipe 9 is preferably the same as the maximum depth D1 of the main groove 8, in this embodiment, the first main groove 11. This reduces the rigidity of the shoulder region Sh, improving the contact of the shoulder region Sh with the road surface during cornering, and ultimately significantly improving handling performance.

[0058] The sipe 9 has at least one raised portion 38 that locally raises the sipe bottom 9s. Such a raised portion 38 appropriately increases the rigidity of the sipe bottom 9s and suppresses the occurrence of cracks at the sipe bottom. In addition, the raised portion 38 can improve handling performance without impairing grip performance.

[0059] In this embodiment, the raised portion 38 is formed in a circular arc shape that protrudes radially outward in the tire radial direction. The raised portion 38 has a raised height h that smoothly increases from both longitudinal ends toward an intermediate position 38c between them. Such raised portion 38 prevents an excessive decrease in the rigidity of the shoulder region Sh.

[0060] As shown in Fig. 5, in this embodiment, one raised portion 38 is provided. In this case, the raised portion 38 is disposed at a middle position 9c (shown in Fig. 5) in the longitudinal direction of the sipe 9. When n raised portions 38 are provided, it is preferable to divide the sipe 9 into n equal parts in the longitudinal direction and provide a raised portion 38 at a middle position in the longitudinal direction of each of the parts (not shown).

[0061] The tread portion 2 of this embodiment has an overlapping portion 39 in which one of the sipes 9 and one of the main grooves 8 (the first main groove 11 in this embodiment) are arranged adjacent to each other in the tire circumferential direction in the shoulder region Sh and overlap with each other in the tire axial direction. It is desirable that one of the sipes 9 and one of the main grooves 8 have the same depth on the first tire circumferential line n passing through the overlapping portion 39. This appropriately reduces the rigidity of the shoulder region Sh, improving the handling performance and grip performance. In this embodiment, the overlapping portion 39 is formed such that the sipes 9 and the first main groove 11 have the same depth over the tire axial direction. The overlapping portion 39 has, for example, the same axial length Lg as the sipe 9.

[0062] The sipes 9 are offset axially outward from the axially intermediate position Si of the shoulder region Sh. This reduces the rigidity at the axially outer side of the shoulder region Sh where the rubber thickness is greater, thereby improving handling performance. In this embodiment, the axially inner end 9i of the sipe 9 is located axially outward from the axially intermediate position Si of the shoulder region Sh.

[0063] In this embodiment, the circumferential groove 10 extends continuously in the tire circumferential direction on the tire equator C. Such a circumferential groove 10 improves drainage performance. The circumferential groove 10 is formed in a zigzag shape in which a first portion 10A inclined to one side with respect to the tire circumferential direction (leftward downward in the figure) and a second portion 10B connected to the first portion 10A and inclined in the opposite direction to the tire circumferential direction are alternately arranged. As a result, each of a pair of groove edges 10e, 10e extending in the longitudinal direction of the circumferential groove 10 is formed such that an outer portion 10s that is on the outer side in the tire axial direction and an inner portion 10t that is on the inner side in the tire axial direction than the outer portion 10s are alternately arranged.

[0064] The circumferential groove 10 includes a notch 40 cut from the tread surface 2a to the first portion 10A and the second portion 10B at an intersection 10k between the first portion 10A and the second portion 10B. Such a notch 40 improves drainage performance and uneven wear resistance.

[0065] The notch portion 40 is arranged so as to be continuous with the outer portion 10s, for example. In this embodiment, the notch portion 40 is formed to include a first edge portion 40a that smoothly continues with the outer portion 10s, and a second edge portion 40b that is inclined at a larger angle with respect to the tire circumferential direction than the first edge portion 40a. The first edge portion 40a suppresses an excessive decrease in rigidity of the tread portion 2 near the tire equator C. When the second edge portion 40b is arranged on the rear side of the first edge portion 40a in the rotational direction N, the second edge portion 40b serves to capture a water film between the road surface and the tread surface 2a and discharge it outside the circumferential groove 10.

[0066] FIG. 7 is a development view of the tread portion 2 of another embodiment. The same components as those of this embodiment are given the same reference numerals, and the description thereof may be omitted. The tread portion 2 of this embodiment is preferably used for a rear tire of a motorcycle. The tread portion 2 may also be used for a front tire.

[0067] As shown in Fig. 7, the tread portion 2 of this embodiment is formed by main grooves 8 and sipes 9, and no circumferential grooves are formed. The main grooves 8 of this embodiment are composed of a first main groove 11 to a sixth main groove 16. In this specification, even in this embodiment, unless otherwise specified, the descriptions of the first main groove 11, the third main groove 13, and the fifth main groove 15 also include the descriptions of the second main groove 12, the fourth main groove 14, and the sixth main groove 16, respectively.

[0068] The first main groove 11 extends in the tire axial direction in one of the shoulder regions Sh, for example, without straddling the tire equator C. The first main groove 11 in this embodiment has an axially inner end 11i closer to the tire equator C than the first main groove 11 in Fig. 1. In this embodiment, the axial distance Lh of the inner end 11i from the tire equator C is preferably within 3% of the tread development width TWe.

[0069] In this embodiment, the widened portion 18 of the first main groove 11 extends to the axially outer end 11e of the first main groove 11. In other words, the first main groove 11 does not have the second narrowed portion 20. Such a first main groove 11 improves drainage performance.

[0070] In this embodiment, the fifth main grooves 15 each extend from the crown region Cr to one of the shoulder regions Sh. Such fifth main grooves 15 appropriately reduce the rigidity of not only the shoulder region Sh but also the crown region Cr.

[0071] For example, a front tire having a tread portion 2 shown in FIG. 1 and a rear tire having a tread portion 2 shown in FIG. 7 constitute a pair of motorcycle tires T.

[0072] It is desirable that the rear tire has more sipes 9 than the front tire. The rear tire has a larger tread development width TWe than the front tire, and therefore the stiffness of the shoulder region Sh is greater. For this reason, the above-mentioned configuration improves the ground contact of the rear tire, and thus improves the handling performance. In the rear tire, two sipes 9 are provided within one pitch P1 of the first main groove 11 (as shown in FIG. 7), and in the front tire, one sipe 9 is provided within one pitch P1 of the first main groove 11 (as shown in FIG. 1). It is desirable that one pitch P1 of the first main groove 11 of the rear tire has the same dimension as one pitch P1 of the first main groove 11 of the front tire.

[0073] The tread portion 2 of the rear tire desirably has a land ratio of 80% or more. This prevents an excessive decrease in the rigidity of the tread portion 2 of the rear tire, and maintains grip performance. In this specification, the land ratio is the ratio (SB / SA) of the surface area SA of the tread surface of the virtual tread portion (not shown) obtained by filling the main grooves 8 or the circumferential grooves 10 to the surface area SB of the tread surface 2a of the tread portion 2.

[0074] A rear tire is a tire that is not greatly affected by the rider's handlebar operation. For such tires, grip performance is considered more important than handling performance. For this reason, in the tread portion 2 of a rear tire, it is preferable that the land ratio of the crown region Cr is equal to or greater than the land ratio of the shoulder region Sh, and it is even more preferable that the land ratio of the crown region Cr is greater than the land ratio of the shoulder region Sh.

[0075] Front tires are tires that are greatly affected by steering. For such tires, handling performance is considered more important than grip performance. For this reason, in the tread portion 2 of a front tire, it is preferable that the land ratio of the shoulder region Sh is equal to or greater than the land ratio of the crown region Cr, and it is even more preferable that the land ratio of the shoulder region Sh is greater than the land ratio of the crown region Cr.

[0076] In order to effectively exert the above-mentioned effect, it is desirable that the tread portion 2 of the front tire has a smaller land ratio than the tread portion 2 of the rear tire.

[0077] Such a tire 1 is formed, for example, by a vulcanization mold (not shown) including a pair of molds. Each of the pair of molds has a dividing position that divides the tread portion 2 into two in the tire axial direction, and each mold vulcanizes and molds the tread portion 2. The dividing positions extend in the tire circumferential direction. The pair of molds forming a front tire have a dividing position at a position spaced apart from the circumferential groove in the tire axial direction. The pair of molds forming a rear tire have a dividing position on the tire equator C.

[0078] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, and can be modified and carried out in various forms. EXAMPLES

[0079] Motorcycle tires having the basic pattern of Fig. 1 or Fig. 7 were produced as prototypes. Then, the handling performance, grip performance, drainage performance, uneven wear resistance, and high-speed durability performance of each sample tire were tested. The common specifications and test methods of each sample tire are as follows:

[0080] <Handling performance, grip performance, resistance to uneven wear, durability> Each sample tire was mounted on a motorcycle (engine displacement 1500cc) under the following conditions. The tire having the tread portion of FIG. 1 was used as a front tire, and the tire having the tread portion of FIG. 7 was used as a rear tire. A test rider used the vehicle to drive on a test course with a dry asphalt road surface, and the handling performance and grip performance at that time were evaluated by the test rider's senses. In addition, the occurrence of uneven wear after driving and the occurrence of cracks at the bottom of grooves and the bottom of sipes were evaluated by the test rider's senses. The results are shown in a score with Comparative Example 1 being 100. For each performance, the higher the numerical value, the better. A score of 95 or more is acceptable. Front tire specifications (size, rim, internal pressure): 110 / 70-13M / C, 13×3.00MT, 200kPa Rear tire specifications (size, rim, internal pressure): 130 / 70-13M / C, 13×3.50MT, 220kPa

[0081] <Drainage performance> Using the above vehicle, a test rider drove a test course on a wet asphalt road surface, and the ease of driving at that time was evaluated by the test rider's senses. The results were shown as a score based on Comparative Example 1 being 100. The higher the score, the better the drainage performance. A score of 95 or more is a pass. The test results are shown in Table 1. The symbols in Table 1 have the following meanings: "A": The first main groove and the second main groove extend from the crown region to the shoulder region. "B": The first and second main grooves extend only in the shoulder region. "C": Sipes are formed only in the shoulder area. "D": No sipes are formed. "E": The first main groove, the second main groove, and the sipes are not connected to each other. "F": The first main groove, the second main groove, and the sipes are connected to each other. "G": The main grooves and sipes do not connect to the tread ends. "H": The main groove connects to the tread edge. "I": Number of sipes on front tires < number of sipes on rear tires "J": Number of sipes on front tire > number of sipes on rear tire "K": The depth of the first main groove on the circumferential line passing through the overlapping portion = the depth of the sipe "L": On the tire circumferential line passing through the overlapping portion, the depth of the first main groove > the depth of the sipe "M": The widened portion of the first main groove becomes a constant width portion.

[0082] [Table 1]

[0083] As a result of the tests, it is understood that the tires (pair of motorcycle tires) of the embodiment are superior in handling performance and grip performance to the tires (pair of motorcycle tires) of the comparative example.

[0084] 1. Motorcycle tires 2 Tread section 8 Main groove 9 Sipe 11 1st main groove 12 2nd main groove Cr Crown region Sh Shoulder area

Claims

1. A tire for a motorcycle, The tire has a tread portion having a pair of tread ends and a carcass having a bias structure, The tread portion includes, in a tread development view, a pair of shoulder regions each having an axial width of 30% of a tread development width on an axially inner side of the pair of tread ends, and a crown region between the pair of shoulder regions, The tread portion is provided with a plurality of main grooves and a plurality of sipes, The main groove includes a first main groove extending from the crown region to one side of the pair of shoulder regions, and a second main groove extending from the crown region to the other side of the pair of shoulder regions, The sipes are formed only in the pair of shoulder regions, The sipe is offset axially outward from a middle position in the shoulder region. Tires for motorcycles.

2. The motorcycle tire according to claim 1 , wherein a maximum depth of the sipes is equal to a maximum depth of the main grooves.

3. One of the sipes and one of the main grooves are arranged adjacent to each other in the tire circumferential direction and have an overlapping portion in the tire axial direction, The motorcycle tire according to claim 1 or 2, wherein one of the sipes and one of the main grooves have the same depth on a first circumferential line passing through the overlapping portion.

4. The motorcycle tire according to claim 1 , wherein the first main groove, the second main groove, and the sipes are arranged without communicating with each other.

5. 5. The motorcycle tire according to claim 1, wherein each of the main grooves terminates without communicating with an end of the tread.

6. The motorcycle tire according to claim 1 , wherein the main groove includes a widened portion in the shoulder region, the widened portion having a groove width increasing from an inner side toward an outer side in the tire axial direction.

7. The motorcycle tire according to claim 6 , wherein the widened portion extends to an axially outer end of the main groove.

8. The motorcycle tire according to claim 1 , wherein the sipe has at least one raised portion formed by locally raising a bottom of the sipe.

9. The motorcycle tire according to claim 8 , wherein the raised portion has an arc shape that protrudes outward in the radial direction of the tire in a cross section along the sipe.

10. A tire comprising a tread portion having a pair of tread ends and a carcass having a bias structure, The tread portion includes, in a tread development view, a pair of shoulder regions each having an axial width of 30% of a tread development width on an axially inner side of the pair of tread ends, and a crown region between the pair of shoulder regions, The tread portion is provided with a plurality of main grooves and a plurality of sipes, The main groove includes a first main groove extending from the crown region to one side of the pair of shoulder regions, and a second main groove extending from the crown region to the other side of the pair of shoulder regions, a pair of motorcycle tires including a front tire and a rear tire, the pair of motorcycle tires including sipes formed only in the pair of shoulder regions, The rear tire has more sipes than the front tire, The tread portion of the rear wheel tire has a land ratio of 80% or more. Motorcycle tire pair.

11. A tire comprising a tread portion having a pair of tread ends and a carcass having a bias structure, The tread portion includes, in a tread development view, a pair of shoulder regions each having an axial width of 30% of a tread development width on an axially inner side of the pair of tread ends, and a crown region between the pair of shoulder regions, The tread portion is provided with a plurality of main grooves and a plurality of sipes, The main groove includes a first main groove extending from the crown region to one side of the pair of shoulder regions, and a second main groove extending from the crown region to the other side of the pair of shoulder regions, a pair of motorcycle tires including a front tire and a rear tire, the pair of motorcycle tires including sipes formed only in the pair of shoulder regions, The rear tire has more sipes than the front tire, The tread portion of the rear wheel tire has a land ratio of the crown region equal to or greater than a land ratio of the shoulder region. Motorcycle tire pair.

12. A tire comprising a tread portion having a pair of tread ends and a carcass having a bias structure, The tread portion includes, in a tread development view, a pair of shoulder regions each having an axial width of 30% of a tread development width on an axially inner side of the pair of tread ends, and a crown region between the pair of shoulder regions, The tread portion is provided with a plurality of main grooves and a plurality of sipes, The main groove includes a first main groove extending from the crown region to one side of the pair of shoulder regions, and a second main groove extending from the crown region to the other side of the pair of shoulder regions, a pair of motorcycle tires including a front tire and a rear tire, the pair of motorcycle tires including sipes formed only in the pair of shoulder regions, The rear tire has more sipes than the front tire, The tread portion of the front tire has a smaller land ratio than the tread portion of the rear tire. Pair of motorcycle tires.

13. A tire comprising a tread portion having a pair of tread ends and a carcass having a bias structure, The tread portion includes, in a tread development view, a pair of shoulder regions each having an axial width of 30% of a tread development width on an axially inner side of the pair of tread ends, and a crown region between the pair of shoulder regions, The tread portion is provided with a plurality of main grooves and a plurality of sipes, The main groove includes a first main groove extending from the crown region to one side of the pair of shoulder regions, and a second main groove extending from the crown region to the other side of the pair of shoulder regions, a pair of motorcycle tires including a front tire and a rear tire, the pair of motorcycle tires including sipes formed only in the pair of shoulder regions, The rear tire has more sipes than the front tire, The tread portion of the front tire has a land ratio in the shoulder region that is equal to or greater than a land ratio in the crown region. Pair of motorcycle tires.

14. A pair of motorcycle tires as described in any one of claims 10 to 13, wherein the maximum depth of the sipes is the same as the maximum depth of the main grooves.

15. One of the sipes and one of the main grooves are arranged adjacent to each other in the tire circumferential direction and have an overlapping portion in the tire axial direction, The pair of motorcycle tires according to claim 10 , wherein one of the sipes and one of the main grooves have the same depth on a first tire circumferential line passing through the overlapping portion.

16. A pair of motorcycle tires as described in any one of claims 10 to 15, wherein the first main groove, the second main groove and the sipes are arranged without communicating with each other.

17. A pair of motorcycle tires as described in any one of claims 10 to 16, wherein each of the main grooves terminates without communicating with the tread end.

18. A pair of motorcycle tyres as claimed in any one of claims 10 to 17, wherein the main groove includes a widening portion in the shoulder region in which the groove width increases from the inside to the outside in the axial direction of the tire.

19. A pair of motorcycle tires as described in claim 18, wherein the widening portion extends to an axially outer end of the main groove.

20. A pair of motorcycle tires as described in any one of claims 10 to 19, wherein the sipes have at least one raised portion that locally raises the bottom of the sipes.

21. A pair of motorcycle tires as described in Claim 20, wherein the raised portion, in a cross section along the sipe, has an arc shape that is convex radially outward in the tire.

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