Motorcycle tires

Abstract

To provide a tire for a motor cycle that can be improved in drainage performance without impairing abrasion resistance and vibration resistance.SOLUTION: In a tire 1 for a motor cycle, a plurality of first lateral grooves 8 are formed in a tread part 2. The first lateral grooves 8 each include a first groove part 11 in a crown part Cr, a second groove part 12 in a first shoulder part S1, and a third groove part 13 joining the first groove part 11 to the second groove part 12. The groove depth and groove width of the third groove part 13 are smaller than the groove depth and groove width of the first groove part 11 and the second groove part 12. Portions corresponding to 80% of a length in a tire axial direction of the third groove parts 13 are arranged in the first shoulder part S1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tire for a motorcycle. [Background technology]

[0002] The following Patent Document 1 describes a motorcycle tire having a main groove and a narrow groove in a tread portion. The main groove includes a first main groove and a second main groove disposed axially outward of the first main groove, and the narrow groove includes an open narrow groove and a semi-open narrow groove. The open narrow groove is disposed such that one end is connected to the first main groove and the other end is connected to the second main groove. [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] In general, in order to improve the drainage of a tire, it is effective to arrange a thick and long groove extending from the crown region of the tread to the shoulder region in the ground contact surface of the tread. However, such a groove may significantly deform the surface of the tread when the tire comes into contact with the ground, which may cause vibration and uneven wear during driving. This tendency is particularly prominent in bias tires, which have lower tread rigidity than radial tires. Therefore, there has been a demand for improving drainage without impairing resistance to uneven wear and vibration.

[0005] The present invention has been devised in consideration of the above-mentioned circumstances, and has as its main object to provide a motorcycle tire that can improve drainage performance without compromising resistance to uneven wear and vibration. [Means for solving the problem]

[0006] The present invention relates to a motorcycle tire having a tread portion, the tread portion including a crown portion which is an area that is 50% of the tread developed width centered on the tire equator, and a first shoulder portion which is an area outside the crown portion, the tread portion having a plurality of first lateral grooves formed therein, each of the first lateral grooves including a first groove portion arranged in the crown portion, a second groove portion arranged in the first shoulder portion, and a third groove portion connecting the first groove portion and the second groove portion, the groove depth and groove width of the third groove portion being smaller than the groove depth and groove width of the first groove portion and the second groove portion, respectively, and 80% or more of the axial length of the third groove portion is arranged in the first shoulder portion.

[0007] In the motorcycle tire according to the present invention, it is preferable that the first groove portion is arranged so as not to straddle the tire equator.

[0008] In the motorcycle tire according to the present invention, it is preferable that the first groove portion, the second groove portion and the third groove portion are inclined in the same direction with respect to the tire axial direction.

[0009] In the motorcycle tire according to the present invention, it is preferable that the groove width of the third groove portion is 15% to 50% of the groove width of the first groove portion and the groove width of the second groove portion.

[0010] In the motorcycle tire according to the present invention, it is preferable that the groove depth of the third groove portion is 15% to 50% of the groove depth of the first groove portion and the groove depth of the second groove portion.

[0011] In the motorcycle tire according to the present invention, it is preferable that the first groove portion includes a first groove edge located on one side in the tire circumferential direction and a second groove edge located on the other side in the tire circumferential direction, the second groove portion includes a first groove edge located on one side in the tire circumferential direction and a second groove edge located on the other side in the tire circumferential direction, and the third groove portion is arranged close to the second groove edge side of the first groove portion and also close to the first groove edge side of the second groove portion.

[0012] In the motorcycle tire according to the present invention, it is preferable that the first lateral groove further includes a fourth groove portion extending from the second groove portion outward in the tire axial direction, and the groove depth and groove width of the fourth groove portion are smaller than the groove depth and groove width of the first groove portion and the second groove portion, respectively.

[0013] In the motorcycle tire according to the present invention, it is preferable that the first groove portion, the second groove portion, the third groove portion and the fourth groove portion are inclined in the same direction with respect to the tire axial direction.

[0014] In the motorcycle tire according to the present invention, it is preferable that the tread portion has a designated tire rotation direction, and the first groove portion is positioned further in the tire rotation direction than the second groove portion.

[0015] The motorcycle tire according to the present invention preferably includes a carcass having a bias structure.

[0016] The present invention relates to a pair of motorcycle tires, the front tire and the rear tire being a motorcycle tire as recited in any one of claims 1 to 10, wherein a land ratio of the tread portion of the rear tire is greater than a land ratio of the tread portion of the front tire. Effect of the Invention

[0017] By employing the above-described configuration, the motorcycle tire of the present invention can improve drainage performance without impairing resistance to uneven wear and vibration resistance. [Brief description of the drawings]

[0018] [Figure 1] 1 is a development view of a tread portion showing one embodiment of the present invention. [Diagram 2] 2A is an enlarged view of a first transverse groove in FIG. 1, and FIG. 2B is a cross-sectional view taken along line AA in FIG. [Diagram 3] FIG. 2 is a cross-sectional view taken along line BB in FIG. [Figure 4] FIG. 2 is an enlarged view of a first transverse groove of FIG. [Diagram 5]FIG. 11 is a development view of a tread portion of another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 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.

[0020] In this embodiment, the tread portion 2 includes a crown portion Cr, which is an area that is 50% of the tread developed width TWe centered on the tire equator C, and a first shoulder portion S1, which is an area on the outer side of the crown portion Cr (on the left side of the crown portion Cr in the figure). The tread portion 2 also includes a second shoulder portion S2, which is an area on the opposite side of the tire equator C from the first shoulder portion S1 (on the right side of the crown portion Cr in the figure). The crown portion Cr is an area that mainly comes into contact with the ground during straight running. The first shoulder portion S1 and the second shoulder portion S2 are areas that mainly come into contact with the ground during cornering. In this specification, the tread developed width TWe is the distance in the tire axial direction between the tread ends Te, Te when the tread portion 2 is developed on a plane.

[0021] A plurality of first lateral grooves 8 are formed in the tread portion 2 of this embodiment. The first lateral grooves 8 include a first groove portion 11 arranged in the crown portion Cr, a second groove portion 12 arranged in the first shoulder portion S1, and a third groove portion 13 connecting the first groove portion 11 and the second groove portion 12. The first lateral grooves 8 extend from the crown portion Cr to the first shoulder portion S1, so that they come into contact with the ground over a wide range from straight running to cornering, improving drainage. In addition, since such first lateral grooves 8 are larger than the ground contact area during running, air sandwiched between the road surface and the grooves is discharged from the non-ground contact portion, so that noise can be improved.

[0022] FIG. 2(a) is an enlarged view of the first lateral groove 8. FIG. 2(b) is a cross-sectional view taken along the line AA in FIG. 1. As shown in FIG. 2, the groove depth D3 and groove width W3 of the third groove portion 13 are smaller than the groove depths D1 and D2 and groove widths W1 and W2 of the first groove portion 11 and the second groove portion 12, respectively. Such a third groove portion 13 suppresses deformation of the first groove portion 11 and the second groove portion 12 and bending of the first lateral groove 8 during running, so that resistance to uneven wear and vibration resistance are not impaired. In addition, in a wide tire 1 in which the thickness of the rubber in the tread portion 2 is likely to be small, the provision of the third groove portion 13 can improve the transient characteristic, which is the stability of handling during cornering. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured on the tire 1 in a normal state.

[0023] 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.

[0024] 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.

[0025] 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."

[0026] The third groove portion 13 is disposed in the first shoulder portion S1 for 80% or more of its axial length L3. Therefore, the rigidity of the first shoulder portion S1, which is subjected to a large camber thrust during cornering, is maintained high, and vibration and uneven wear during driving are suppressed. In addition, in such a tire 1, the concentration of flexure is mitigated, and therefore the occurrence of cracks at the groove bottom is suppressed. In this embodiment, the third groove portion 13 is disposed in the first shoulder portion S1 for 100% of its axial length L3.

[0027] The tread portion 2 of this embodiment is suitably used for a front tire of a motorcycle. The tread portion 2 of this embodiment may also be used for a rear tire.

[0028] Fig. 3 is a cross-sectional view taken along line BB in Fig. 1. As shown in Fig. 3, 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.

[0029] 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.

[0030] The carcass 6 is composed of, for example, two carcass plies 6A, 6B arranged inside and outside in the tire radial direction. Each carcass ply 6A, 6B has, for example, 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 carcass ply 6A, 6B. Note that, compared with a tire 1 having a so-called radial structure, a tire 1 having a bias structure has a characteristic that the rigidity of the tread portion 2 is small and it is easily bent. In the present invention, by having the above-mentioned configuration, it is possible to improve vibration resistance and uneven wear resistance not only in the tire 1 having a radial structure but also in the tire 1 having a bias structure.

[0031] The band layer 7 is made of one or more band plies (one band ply in this embodiment) formed by spirally winding a band cord (not shown) at an angle of 5 degrees or less with respect to the circumferential direction of the tire. Well-known materials are used for the band ply.

[0032] 1, the tread portion 2 of this embodiment is specified to have a tire rotation direction N. In this embodiment, the first groove portions 11 are positioned further in the tire rotation direction N than the second groove portions 12. Therefore, water in the first lateral grooves 8 utilizes the rotation of the tire 1 to flow from the tire equator C side to the tread end Te side and is smoothly discharged, improving drainage performance.

[0033] The first lateral grooves 8 are provided, for example, on both sides of the tire equator C. The first lateral grooves 8 in this embodiment are arranged alternately in the tire circumferential direction on either side of the tire equator C. In this embodiment, the first lateral grooves 8 are arranged without straddling the tire equator C. In other words, the first groove portions 11 are arranged without straddling the tire equator C. Such a layout maintains the tread rigidity in the vicinity of the tire equator C where a large ground contact pressure acts, and maintains resistance to uneven wear and vibration. In this specification, regarding grooves and sipes (hereinafter referred to as "grooves, etc.") of the same shape arranged on both sides of the tire equator C, the grooves, etc. on the first shoulder portion S1 side will be described, and the description of the grooves, etc. on the second shoulder portion S2 side may be omitted.

[0034] As shown in FIG. 2(a), the first groove portion 11, the second groove portion 12, and the third groove portion 13 are inclined in the same direction with respect to the tire axial direction, for example. This allows water to flow more smoothly in the first lateral groove 8. The angle θ1 of the first groove portion 11 with respect to the tire axial direction, the angle θ2 of the second groove portion 12 with respect to the tire axial direction, and the angle θ3 of the third groove portion 13 with respect to the tire axial direction are each 20 to 60 degrees. The absolute values ​​of the differences (|θ1-θ2|, |θ2-θ3|, |θ3-θ1|) between the angle θ1 of the first groove portion 11, the angle θ2 of the second groove portion 12, and the angle θ3 of the third groove portion 13 are 30 to 50 degrees. In this specification, the angles θ1 to θ3 of the groove portions 11 to 13 are the average values ​​between their maximum and minimum values.

[0035] The first groove portion 11 includes, for example, a first groove edge 11e located on one side in the tire circumferential direction (lower side in the figure) and a second groove edge 11i located on the other side in the tire circumferential direction (upper side in the figure). The second groove edge 11i of the first groove portion 11 includes, for example, a bent portion F, and an angle α with respect to the tire axial direction changes locally through the bent portion F. The second groove edge 11i includes an outer portion 15 located on the outer side in the tire axial direction from the bent portion F, and an inner portion 16 located on the inner side in the tire axial direction from the bent portion F. The first groove edge 11e of the first groove portion 11 extends smoothly without having a bent portion. The first groove edge 11e and the second groove edge 11i are connected to, for example, an inner end 8i of the first lateral groove 8. In this specification, the inner end 8i is the innermost end in the tire axial direction of the groove center line 8c of the first lateral groove 8. In addition, in this specification, the inner end 8i includes an arc portion with a curvature radius r of 2 mm or less.

[0036] The first groove edge 11e and the outer portion 15 include, for example, an arc-shaped portion R that is convex toward one side in the tire circumferential direction. In this embodiment, the arc-shaped portion R of the first groove edge 11e and the outer portion 15 is formed to be convex toward the rear side in the tire rotation direction N. The inner portion 16 in this embodiment extends linearly.

[0037] Fig. 4 is an enlarged view of the first lateral groove 8. As shown in Fig. 4, the angle α1 of the inner portion 16 relative to the tire axial direction is smaller than the angle α2 of the first groove edge 11e relative to the tire axial direction. In other words, the first groove portion 11 formed in the inner portion 16 is formed so that the groove width w becomes smaller toward the inner end 8i. Such a first groove portion 11 can smoothly guide water and air into the first groove portion 11 by utilizing the rotation of the tire 1 while suppressing the decrease in the tread rigidity of the crown portion Cr.

[0038] The second groove portion 12 includes, for example, a first groove edge 12e located on one side in the tire circumferential direction and a second groove edge 12i located on the other side in the tire circumferential direction. The first groove edge 12e and the second groove edge 12i include, for example, an arc-shaped portion R that is a convex arc in either direction in the tire circumferential direction. In this embodiment, the arc-shaped portion R of the first groove edge 12e and the second groove edge 12i is formed to be convex toward the rear side in the tire rotation direction N.

[0039] In this embodiment, the third groove portion 13 is disposed closer to the second groove edge 11i of the first groove portion 11 and closer to the first groove edge 12e of the second groove portion 12. In other words, the first lateral groove 8 of this embodiment is formed such that an imaginary line 12k, which is a smooth extension of the groove center line 12c of the second groove portion 12 toward the inside in the tire axial direction, is located further back in the tire rotation direction N than the third groove portion 13. In this embodiment, the position at which the first lateral groove 8 is distorted when the tire comes into contact with the ground can be shifted in the tire circumferential direction, thereby suppressing the occurrence of groove bottom cracks.

[0040] The third groove portion 13 includes, for example, a first groove edge 13e located on one side in the tire circumferential direction and a second groove edge 13i located on the other side in the tire circumferential direction. The first groove edge 13e of the third groove portion 13 is formed, for example, to include a crank-shaped portion K extending in a crank shape toward the second groove edge 13i side of the third groove portion 13. The second groove edge 13i of the third groove portion 13 is formed, for example, to include a circular arc-shaped portion R convex on the opposite side to the second groove edge 11i of the first groove portion 11.

[0041] In this specification, the third groove portion 13 is defined as a portion where the groove width w suddenly becomes smaller between the first groove portion 11 and the second groove portion 12. The third groove portion 13 refers to a portion where the rate of change in the groove width w per unit length of the groove is 0.4 or more.

[0042] As shown in FIG. 2(a), the groove width W3 of the third groove portion 13 is preferably 15% or more of the groove width W1 of the first groove portion 11 and the groove width W2 of the second groove portion 12, more preferably 20% or more, more preferably 50% or less, and even more preferably 45% or less. Since the groove width W3 of the third groove portion 13 is 15% or more of the groove width W1 of the first groove portion 11 and the groove width W2 of the second groove portion 12, drainage performance is maintained. Since the groove width W3 of the third groove portion 13 is 50% or less of the groove width W1 of the first groove portion 11 and the groove width W2 of the second groove portion 12, uneven wear resistance and vibration resistance are improved. In this specification, the groove width W3 of the third groove portion 13 is the minimum groove width of the third groove portion 13. In this specification, the groove width W1 of the first groove portion 11 and the groove width W2 of the second groove portion 12 are the maximum groove widths of the first groove portion 11 and the second groove portion 12. Although not particularly limited, the groove width W1 of the first groove portion 11 is 3.5 to 7.0 mm.

[0043] As shown in FIG. 2(b), from the same viewpoint, the groove depth D3 of the third groove portion 13 is preferably 15% or more, more preferably 20% or more, more preferably 50% or less, and even more preferably 45% or less of the groove depth D1 of the first groove portion 11 and the groove depth D2 of the second groove portion 12. In this specification, the groove depth D3 of the third groove portion 13 is the minimum groove depth of the third groove portion 13. In this specification, the groove depth D1 of the first groove portion 11 and the groove depth D2 of the second groove portion 12 are the maximum groove depths of the first groove portion 11 and the second groove portion 12. Although not particularly limited, the groove depth D1 of the first groove portion 11 is 3.0 to 7.5 mm.

[0044] As shown in FIG. 2(a), the length L3 of the third groove portion 13 is preferably 10% or more of the axially developed width Ws (shown in FIG. 1) of the first shoulder portion S1, more preferably 15% or more, and more preferably 30% or less, and even more preferably 25% or less. 。

[0045] The first lateral groove 8 further includes a fourth groove portion 14 extending from the second groove portion 12 toward the outside in the tire axial direction. The groove depth D4 and groove width W4 of the fourth groove portion 14 are formed smaller than the groove depths D1 and D2 and groove widths W1 and W2 of the first groove portion 11 and the second groove portion 12, respectively. Such a fourth groove portion 14 also enhances drainage while suppressing the deterioration of uneven wear resistance and vibration resistance. In addition, the fourth groove portion 14 comes into contact with the ground during cornering when the camber angle is large. By setting the groove depth D4 and groove width W4 of such a fourth groove portion 14 as described above, the rigidity of the tread surface (tread surface 2a) at the time of contact with the ground is prevented from decreasing even during cornering when the camber angle is large, so that the vehicle body can be raised smoothly, resulting in light handling.

[0046] The groove depth D4 and groove width W4 of the fourth groove portion 14 are, for example, substantially the same as the groove depth D3 and groove width W3 of the third groove portion 13. Such a fourth groove portion 14 effectively exerts the above-mentioned action. The term "substantially the same" means that the difference between the groove depth D4 of the fourth groove portion 14 and the groove depth D3 of the third groove portion 13 is within 2 mm. Also, it means that the difference between the groove width W4 of the fourth groove portion 14 and the groove width W3 of the third groove portion 13 is within 2 mm.

[0047] In this embodiment, the fourth groove portions 14 are inclined with respect to the tire circumferential direction in the same direction as the second groove portions 12. Such fourth groove portions 14 maintain a smooth flow of water in the first lateral grooves 8.

[0048] The axially outer end 14a of the fourth groove portion 14 is disposed in the first shoulder portion S1. In other words, the fourth groove portion 14 terminates at the first shoulder portion S1 without straddling the tread end Te. Such a fourth groove portion 14 suppresses a decrease in the rigidity of the tread portion 2 on the tread end Te where a large lateral force acts.

[0049] The fourth groove portion 14 is disposed close to the second groove edge 12i of the second groove portion 12. The fourth groove portion 14 includes a first groove edge 14e located on one side in the tire circumferential direction and a second groove edge 14i located on the other side in the tire circumferential direction. The second groove edge 14i of the fourth groove portion 14 extends to form a single arc together with the second groove edge 12i of the second groove portion 12. The first groove edge 14e of the fourth groove portion 14 is formed to include a crank-shaped portion K extending in a crank shape toward the second groove edge 14i of the fourth groove portion 14.

[0050] As shown in FIG. 2(b), the groove bottom 11s of the first groove portion 11 and the groove bottom 13s of the third groove portion 13 are smoothly connected. The groove bottom 12s of the second groove portion 12 and the groove bottom 13s of the third groove portion 13 are smoothly connected. Furthermore, the groove bottom 12s of the second groove portion 12 and the groove bottom 14s of the fourth groove portion 14 are smoothly connected. Such a first lateral groove 8 suppresses the occurrence of groove bottom cracks and smooths the flow of water in the groove. The above-mentioned "smooth connection" refers to a mode in which each of the groove bottoms 11s to 14s is formed by an inner arc portion 17a that is convex inward in the tire radial direction and an outer arc portion 17b that is disposed outward in the tire radial direction from the inner arc portion 17a and convex outward in the tire radial direction.

[0051] 1, the tread portion 2 is further provided with, for example, a circumferential groove 20, a second lateral groove 21, a third lateral groove 22, and a sipe 23. In this specification, grooves such as the first lateral groove 8 and the circumferential groove 20 are groove-like bodies with a maximum groove width exceeding 1.5 mm. In this specification, a sipe is a cut-like body with a maximum width of 1.5 mm or less.

[0052] The circumferential groove 20 extends continuously in the tire circumferential direction on the tire equator C. In this embodiment, the circumferential groove 20 is formed in a zigzag shape in which a first portion 20A inclined to one side with respect to the tire circumferential direction (downward to the left in the figure) and a second portion 20B connected to the first portion 20A and inclined in the opposite direction to the tire circumferential direction are alternately arranged.

[0053] The circumferential groove 20 includes a pair of longitudinally extending groove edges 20e, 20e. The circumferential groove 20 extends in a zigzag pattern on the tire equator C, so that each groove edge 20e, 20e is formed with an outer portion 25, either of which is on the outer side in the tire axial direction, and an inner portion 26, which is on the inner side in the tire axial direction than the outer portion 25, alternately formed in the tire circumferential direction. At the connection portion between the first portion 20A and the second portion 20B, the outer portion 25 is formed to include an axial portion J extending in the tire axial direction. Such an axial portion J collects water between the road surface and the tread surface 2a in the circumferential groove 20, improving drainage.

[0054] In this embodiment, the second lateral grooves 21, the third lateral grooves 22, and the sipes 23 are disposed on both sides of the tire equator C. For example, the second lateral grooves 21, the third lateral grooves 22, and the sipes 23 are inclined toward the rear of the tire rotation direction N from the tire equator C toward the tread end Te. In this embodiment, the second lateral grooves 21, the third lateral grooves 22, and the sipes 23 extend in a convex arc toward the rear of the tire rotation direction N. For example, the second lateral grooves 21, the third lateral grooves 22, and the sipes 23 terminate within the first shoulder portion S1 without communicating with the tread end Te.

[0055] The second lateral grooves 21 extend, for example, from the crown portion Cr to the first shoulder portion S1. In this embodiment, the second lateral grooves 21 are formed to have a greater axial length than the first lateral grooves 8. The inner ends 21i of the second lateral grooves 21 are disposed, for example, closer to the tire equator C than the inner ends 8i of the first lateral grooves 8.

[0056] The third lateral grooves 22 extend, for example, from the crown portion Cr to the first shoulder portion S1. The third lateral grooves 22 are formed to have an axial length smaller than that of the first lateral grooves 8. The inner ends 22i of the third lateral grooves 22 are disposed closer to the tread edge Te than the inner ends 8i of the first lateral grooves 8. The axial outer ends 22e of the third lateral grooves 22 are disposed closer to the tire equator C than the outer ends 8e (shown in FIG. 4) of the first lateral grooves 8.

[0057] 4, the sipes 23 are disposed in the first shoulder portion S1. An axially inner end 23i of the sipe 23 is disposed in the first shoulder portion S1. An axially outer end 23e of the sipe 23 is disposed between an outer end 8e of the first lateral groove 8 and an outer end 22e of the third lateral groove 22.

[0058] FIG. 5 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.

[0059] 5, the tread portion 2 of this embodiment includes a first lateral groove 8, a second lateral groove 21, a third lateral groove 22, and a sipe 23. In this embodiment, the tread portion 2 does not have a circumferential groove. For example, two sipes 23 are provided between the first lateral groove 8 and the second lateral groove 21.

[0060] In this embodiment, the inner end 21i of the second lateral groove 21 is located axially inward of the inner end 21i of the second lateral groove 21 of this embodiment. This suppresses a decrease in drainage performance. The shortest distance Lb between the inner end 21i of the second lateral groove 21 and the tire equator C is preferably 0.5% or more of the developed width Wc of the crown portion Cr, more preferably 0.7% or more, more preferably 2.5% or less, and even more preferably 2.0% or less.

[0061] A motorcycle is fitted with front and rear tires (not shown). The rear tire is a tire that is not significantly affected by the rider's steering. For such tires, grip performance is considered more important than handling performance. For this reason, it is desirable for the land ratio of the tread portion 2 of the rear tire to be greater than the land ratio of the tread portion 2 of the front tire. In particular, it is desirable for the land ratio of the tread portion 2 of the rear tire to be 80% or more.

[0062] 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

[0063] Motorcycle tires having the basic pattern shown in Fig. 1 were prototyped. Each sample tire was tested for handling performance, drainage performance, uneven wear resistance, and high-speed durability. The common specifications and test methods for each sample tire are as follows:

[0064] <Handling performance, resistance to uneven wear, durability, vibration resistance, noise level> Each sample tire was mounted on the front wheel of a motorcycle (engine displacement 1500cc) under the following conditions. A tire of the same pattern was used for the rear tire. A test rider drove the vehicle on a test course with a dry asphalt road surface, and evaluated the lightness of handling, the degree of vibration and noise 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 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, 225kPa

[0065] <Drainage> 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 with Comparative Example 1 being 100. The higher the score, the better the drainage. 95 or more is a pass. The test results are shown in Table 1. "A" in Table 1 means that the second groove portion is located as shown in FIG. The "B" means that the second groove portion is located in the crown portion. The "C" means that the third groove portion is located as shown in FIG. The "D" means that the third groove is located in the crown portion. The "E" means that 80% of the length of the third groove is located in the first shoulder portion. The "F" means that 70% of the length of the third groove is located in the first shoulder portion. The letter "G" means that the groove bottom of each groove portion of the first transverse groove is in the form shown in FIG. 2(b). The "H" means that the groove bottoms of the first transverse grooves are connected in a straight line. The "I" means that the inner side of the first groove portion is in the form shown in FIG. The "J" means that the inner portion of the first groove portion extends with a uniform width. The third groove portions have the same length.

[0066] [Table 1]

[0067] As a result of the test, it is understood that the tires of the examples have improved drainage performance without impairing resistance to uneven wear and vibration, as compared with the tires of the comparative examples.

[0068] 1. Motorcycle tires 2 Tread section 8 First Yokomizo 11 First groove 12 Second groove 13 Third Groove Cr Crown part S1 First shoulder section L3 Length of the third groove

Claims

1. A motorcycle tire having a tread portion, The tread portion includes a crown portion that is a region that is 50% of a tread developed width centered on a tire equator, and a first shoulder portion that is a region outside the crown portion, A plurality of first lateral grooves are formed in the tread portion, Each of the first lateral grooves includes a first groove portion disposed in the crown portion, a second groove portion disposed in the first shoulder portion, and a third groove portion connecting the first groove portion and the second groove portion, a groove depth and a groove width of the third groove portion are smaller than the groove depth and the groove width of the first groove portion and the second groove portion, respectively; 80% or more of the axial length of the third groove portion is disposed in the first shoulder portion. Tires for motorcycles.

2. The motorcycle tire according to claim 1 , wherein the first groove portion is disposed so as not to straddle a tire equator.

3. The motorcycle tire according to claim 1 or 2, wherein the first groove portion, the second groove portion and the third groove portion are inclined in the same direction with respect to the tire axial direction.

4. 4. The motorcycle tire according to claim 1, wherein a groove width of the third groove portion is 15% to 50% of a groove width of the first groove portion and a groove width of the second groove portion.

5. 5. The motorcycle tire according to claim 1, wherein a groove depth of the third groove portion is 15% to 50% of a groove depth of the first groove portion and a groove depth of the second groove portion.

6. The first groove portion includes a first groove edge located on one side in the tire circumferential direction and a second groove edge located on the other side in the tire circumferential direction, The second groove portion includes a first groove edge located on one side in the tire circumferential direction and a second groove edge located on the other side in the tire circumferential direction, 6. The motorcycle tire according to claim 1, wherein the third groove portion is disposed closer to the second groove edge side of the first groove portion and also closer to the first groove edge side of the second groove portion.

7. The first lateral groove further includes a fourth groove portion extending from the second groove portion toward an outer side in the tire axial direction, The motorcycle tire according to claim 1 , wherein a groove depth and a groove width of the fourth groove portion are smaller than a groove depth and a groove width of the first groove portion and a groove width of the second groove portion, respectively.

8. The motorcycle tire according to claim 7 , wherein the first groove portion, the second groove portion, the third groove portion and the fourth groove portion are inclined in the same direction with respect to the tire axial direction.

9. The tread portion has a specified tire rotation direction, The motorcycle tire according to claim 1 , wherein the first groove portion is positioned further in a tire rotational direction than the second groove portion.

10. 10. The motorcycle tire according to claim 1, further comprising a carcass having a bias structure.

11. A pair of motorcycle tires, each of which is a front tire and a rear tire, comprising the motorcycle tire according to any one of claims 1 to 10, a land ratio of the tread portion of the rear tire is greater than a land ratio of the tread portion of the front tire; Pair of motorcycle tires.

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