tire

Abstract

To achieve both low air resistance and excellent wet grip performance.SOLUTION: A tread of a tire comprises: a major groove extending in a tire circumferential direction; a shoulder land part which is formed at the outer side in a tire width direction in comparison with the major groove; a shoulder groove which extends from the major groove side of the shoulder land part, exceeding a tread ground contact end, to an outer side in the tire width direction; and a shoulder siping which extends from the major groove side of the shoulder land part, exceeding the tread ground contact end, to the outer side in the tire width direction. A minimal length (L1) from a tire equator to the outer side end of the shoulder groove in the tire width direction along a top face of the tread is 1.10-1.20 times of a minimal length (L2) from the tire equator to the tread ground contact end along the top face of the tread, and a minimal length (L3) from the tire equator to the outer side end of the shoulder siping in the tire width direction along the top face of the tread is longer than the length (L1), and 1.20-1.35 times of the length (L2).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tire, and more particularly to a tire having grooves and sipes formed in shoulder land portions of the tread. [Background technology]

[0002] Conventionally, tires in which grooves and sipes are formed in shoulder land portions arranged on both sides of the width direction of the tread are widely known. For example, Patent Document 1 discloses a one-way tire having a tread including a center rib and shoulder ribs, in which the width of the lateral grooves formed in the center rib is 0.4 mm to 1.6 mm, and the width of the lateral grooves formed in the shoulder ribs is 2 mm to 8 mm. Patent Document 1 describes the effect that the air column resonance sound and pitch noise can be reduced in a balanced manner while ensuring the drainage performance of the tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-78984 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the configuration of the grooves and sipes formed in the shoulder land portion is important in improving the wet grip performance of the tire, but as a result of the study by the present inventor, it was found that it also has a large effect on the air resistance of the tire. In a tire in which grooves and sipes are formed in the shoulder land portion of the tread, it is not easy to achieve both low air resistance and good wet grip performance, and conventional tires including the tire of Patent Document 1 still have room for improvement in terms of achieving both of these performances.

[0005] An object of the present invention is to provide a tire which can achieve both low air resistance and good wet grip performance. [Means for solving the problem]

[0006] A tire according to the present invention is a tire having a tread, the tread having main grooves extending in the tire circumferential direction, a shoulder land portion formed on the tire width direction outer side of the main groove, a shoulder groove extending from the main groove side of the shoulder land portion beyond the tread ground contact edge to the tire width direction outer side, and a shoulder sipe extending from the main groove side of the shoulder land portion beyond the tread ground contact edge to the tire width direction outer side, characterized in that the shortest distance (L1) along the upper surface of the tread from the tire equator to the tire width direction outer end of the shoulder groove is 1.10 to 1.20 times the shortest distance (L2) along the upper surface of the tread from the tire equator to the tread ground contact edge, and the shortest distance (L3) from the tire equator to the tire width direction outer end of the shoulder sipe is longer than the distance (L1) and is 1.20 to 1.35 times the distance (L2). Effect of the Invention

[0007] The tire according to the present invention can achieve both low air resistance and good wet grip performance. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view showing a schematic view of a portion of a tread in a tire that is an example of an embodiment. [Diagram 2] 1 is a diagram showing a schematic view of a portion of a tire widthwise cross section according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An example of an embodiment of a tire according to the present invention will be described in detail below with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. Furthermore, the present invention includes configurations that selectively combine the respective components of the multiple embodiments and modified examples described below. In this specification, the "main tire rotation direction" refers to the rotation direction when a vehicle on which the tire is mounted moves forward.

[0010] Fig. 1 is a plan view showing a schematic view of a part of a tread 2 of a tire 1 according to an embodiment, and Fig. 2 is a schematic view of a part of a widthwise cross section of the tire 1. In Fig. 1, dot hatching is applied to the upper surface of a land portion formed in the tread 2. The upper surface of the land portion means the surface facing outward in the tire radial direction.

[0011] As shown in Figs. 1 and 2, a tire 1 includes a tread 2, which is a portion that comes into contact with the road surface, and a pair of sidewalls 3 that extend radially inward from both ends of the tread 2 in the width direction of the tire. The tread 2 is formed of a tread rubber 2A, and the sidewalls 3 are formed of a sidewall rubber 3A. The tire 1 also includes a pair of beads (not shown) that are fixed to a wheel rim. The tread 2, the sidewalls 3, and the beads are formed in an annular shape along the circumferential direction of the tire. The sidewalls 3 and the beads form the left and right side surfaces of the tire 1.

[0012] The tread 2 has a main groove 10 extending in the tire circumferential direction, and a shoulder rib 11 formed on the outer side of the main groove 10 in the tire width direction. As will be described in detail later, the shoulder rib 11 is formed with a shoulder groove 14 and a shoulder sipe 15 extending in a direction intersecting with the main groove 10. In the example shown in FIG. 1, the shoulder groove 14 and the shoulder sipe 15 are alternately formed at regular intervals in the tire circumferential direction. The shoulder groove 14 and the shoulder sipe 15 are spaced apart in the tire circumferential direction, but in the tire widthwise cross-sectional view of FIG. 2, the position of the bottom surface 14c of the shoulder groove 14 is shown by a dashed line, and the position of the bottom surface 15c of the shoulder sipe 15 is shown by a two-dot chain line.

[0013] The tire 1 is a pneumatic tire filled with air at a predetermined pressure. The tire 1 generally includes a carcass 4 and a belt 5. The carcass 4 is a cord layer covered with rubber, and forms the framework of the tire 1 that can withstand load, impact, air pressure, and the like. The belt 5 is a reinforcing band disposed between the tread rubber 2A and the carcass 4, and tightens the carcass 4 to increase the rigidity of the tire 1. An inner liner 6, which is a rubber layer for retaining air pressure, is provided on the inner peripheral surface of the carcass 4.

[0014] The tread 2 has a ground contact end E. In this specification, the ground contact end E refers to both ends in the tire width direction of the area that comes into contact with a flat road surface when an unused tire 1 is mounted on a standard rim and filled with air to achieve a standard internal pressure, and a load of 70% of the standard load (maximum load capacity) at the standard internal pressure is applied. Shoulder ribs 11 are formed on both sides in the width direction of the tread 2, and the ground contact end E exists on the upper surface of each shoulder rib 11. In this specification, a position along the end 14b of each shoulder groove 14 is defined as the outer end of the shoulder rib 11 in the tire width direction. The portion located between the outer end of the shoulder rib 11 in the tire width direction and the sidewall 3 is generally called the shoulder of the tire 1.

[0015] Here, a "regular rim" is a rim determined by the tire standard, which is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. "Regular internal pressure" is "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. "Regular load" is "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO.

[0016] A plurality of main grooves 10 extending in the tire circumferential direction are formed in the tread 2. The main grooves 10 function as drainage channels that remove rainwater and the like that exists between the tread 2 and the road surface. In this embodiment, four main grooves 10 are formed in the tread 2. The four main grooves 10 have, for example, approximately the same depth and approximately the same width. The tread 2 has a plurality of land portions defined by the four main grooves 10. The land portions are protruding portions that protrude from a reference surface of the tread 2 toward the outside in the tire radial direction. The reference surface is a virtual surface that follows the bottom surface of the main grooves 10, and means the surface of the tread 2 when no land portions exist.

[0017] The tread 2 has a shoulder rib 11, a center rib 12, and an intermediate rib 13 as the land portion. The shoulder rib 11 is formed on both sides in the width direction of the tread 2. The center rib 12 is formed in the center of the tread 2 in the width direction, and the intermediate ribs 13 are formed between the shoulder rib 11 and each center rib 12. Each rib is a belt-shaped land portion in a plan view that is continuous in the tire circumferential direction, and the shoulder rib 11 and the center rib 12 are partitioned by the first main groove 10a, and the center rib 12 and the intermediate rib 13 are partitioned by the second main groove 10b.

[0018] The center rib 12 is formed on the tire equator CL along the tire circumferential direction. The tire equator CL means a line along the tire circumferential direction passing through the center in the tire width direction. The intermediate ribs 13 are formed on both sides of the center rib 12 in the tire width direction, separated by the main groove 10b. That is, the two intermediate ribs 13 are arranged to sandwich the center rib 12 via the main groove 10b. In addition, the shoulder ribs 11 are formed on the outer side of the intermediate ribs 13 in the tire width direction, with the main groove 10a between them.

[0019] At least one of grooves and sipes extending in a direction intersecting the main grooves 10 may be formed in the center rib 12 and the intermediate rib 13. Note that a center block and an intermediate block partitioned into a plurality of blocks may be provided instead of the center rib 12 and the intermediate rib 13. In the present invention, the tread pattern other than that of the shoulder ribs 11 is not particularly limited.

[0020] The configuration of the shoulder rib 11, particularly the configuration of the shoulder grooves 14 and shoulder sipes 15 formed in the shoulder rib 11, will be described in detail below.

[0021] The tread 2 has two shoulder ribs 11, a shoulder groove 14 extending from the main groove 10 side of the shoulder rib 11 beyond the ground contact edge E to the outside in the tire width direction, and a shoulder sipe 15 extending from the main groove 10 side of the shoulder rib 11 beyond the ground contact edge E to the outside in the tire width direction. A plurality of shoulder grooves 14 and shoulder sipes 15 are formed in each shoulder rib 11 arranged on both sides in the width direction of the tread 2. In this embodiment, the shoulder groove 14 is not connected to the main groove 10b, and the shoulder rib 11 is continuous in the tire circumferential direction at the inner end in the tire width direction.

[0022] The shoulder groove 14 functions as a drainage channel together with the main groove 10, and contributes to improving the drainage and wet grip performance of the tire 1. In addition, the shoulder groove 14 and the shoulder sipes 15 also affect the rigidity of the shoulder rib 11, so that a reduction in their volumes not only reduces the drainage performance, but also increases the rigidity of the shoulder rib 11, shortening the contact length, which may reduce the wet grip performance, especially under high load conditions. As will be described in detail later, the tire 1 is designed to reduce air resistance while ensuring good wet grip performance by limiting the length of the shoulder groove 14 and the shoulder sipes 15 to a specific range.

[0023] 1, the shoulder grooves 14 and shoulder sipes 15 are formed symmetrically with respect to the tire equator CL in each shoulder rib 11, but the shoulder grooves 14 and shoulder sipes 15 do not have to be formed symmetrically. The shoulder grooves 14 and shoulder sipes 15 may be arranged in a staggered pattern along the tire circumferential direction in each shoulder rib 11, rather than being aligned in the tire width direction. However, from the viewpoint of achieving both low air resistance and good wet grip performance of the tire 1, it is preferable that the shoulder grooves 14 and shoulder sipes 15 are formed in each shoulder rib 11 so as to satisfy the length relationship described below.

[0024] The shoulder rib 11 is formed further outward in the tire width direction than the main groove 10a, and extends beyond the ground contact edge E of the tread 2 toward the outside in the tire width direction. The upper surface of the shoulder rib 11 is curved significantly toward the inside in the tire radial direction outside the ground contact edge E. The shoulder grooves 14 and shoulder sipes 15 are generally formed shallower than the main groove 10. There are no particular limitations on the relationship in depth between the shoulder grooves 14 and shoulder sipes 15, but in this embodiment, they are approximately the same depth at their deepest portions.

[0025] Both the shoulder groove 14 and the shoulder sipe 15 are grooves formed in the shoulder rib 11, but the shoulder groove 14 is a wide groove and the shoulder sipe 15 is a thin groove. In general, they are recognized as different. In this specification, a groove with a width of 2.5 mm or more is defined as the shoulder groove 14, and a thin groove with a width of 1.0 mm or less is defined as the shoulder sipe 15. For example, the width (W4) of the shoulder groove 14 is 2.5 mm to 7.0 mm, and the width (W5) of the shoulder sipe 15 is 0.3 mm to 1.0 mm. The widths (W4, W5) refer to the length along the tire circumferential direction between the opposing groove walls.

[0026] The shoulder groove 14 and the shoulder sipe 15 extend in a direction intersecting with the main groove 10a and are formed parallel to each other. In this specification, the end of the shoulder groove 14 located on the inner side in the tire width direction is referred to as a starting end 14a, and the end of the shoulder groove 14 located on the outer side in the tire width direction is referred to as a terminal end 14b. Similarly, the end of the shoulder sipe 15 located on the inner side in the tire width direction is referred to as a starting end 15a, and the end of the shoulder sipe 15 located on the outer side in the tire width direction is referred to as a terminal end 15b. The shoulder groove 14 and the shoulder sipe 15 are inclined with respect to the tire width direction so that the terminal ends 14b, 15b are located further rearward in the tire main rotation direction than the starting ends 14a, 15a.

[0027] The shoulder grooves 14 and the shoulder sipes 15 may be formed in a substantially straight line in a plan view of the tread 2, or may be gently curved so as to be convex toward the rear in the main rotation direction of the tire. The shoulder grooves 14 and the shoulder sipes 15 are, for example, arranged alternately in the tire circumferential direction and at equal intervals. In the example shown in FIG. 1, the same number of shoulder grooves 14 and shoulder sipes 15 are formed, but the number of shoulder grooves 14 and shoulder sipes 15 may be different. For example, two shoulder sipes 15 may be arranged between two shoulder grooves 14.

[0028] Each of the shoulder grooves 14 has the same tire width direction length (L4). Similarly, each of the shoulder sipes 15 has the same tire width direction length (L5). Here, the length (L4) means the length from the start end 14a to the end end 14b of the shoulder groove 14 along the tire width direction, and the length (L5) means the length from the start end 15a to the end end 15b of the shoulder sipe 15 along the tire width direction. The shoulder sipe 15 is preferably formed longer than the shoulder groove 14.

[0029] An example of the length (L4) of the shoulder groove 14 is 30 mm to 45 mm, and preferably 35 mm to 40 mm. An example of the length (L5) of the shoulder sipe 15 is 40 mm to 55 mm, and preferably 45 mm to 50 mm. Note that, within a range that does not impair the object of the present invention, the lengths (L4) of the shoulder grooves 14 adjacent to each other in the tire circumferential direction may be different (the same applies to the shoulder sipes 15). The shoulder sipes 15 extend beyond the terminal ends 14b of the shoulder grooves 14 toward the outside in the tire width direction, and the terminal ends 15b are located on the shoulder of the tire 1.

[0030] Each of the shoulder grooves 14 may have the same width (W4), but in this embodiment, there are two or more groups of shoulder grooves 14 with different widths (W4). The number of groups of shoulder grooves 14 with different widths (W4) is, for example, 3 to 7. The shoulder rib 11 may have a plurality of regions in which the shoulder grooves 14 are arranged so that the width (W4) gradually increases along the tire circumferential direction. Each of the shoulder sipes 15 has the same width (W5), but similar to the shoulder grooves 14, there may be two or more groups of shoulder sipes 15 with different widths (W5).

[0031] The width (W4) of the shoulder groove 14 is, for example, 2.5 mm to 7.0 mm, and preferably 2.5 mm to 5.5 mm. The width (W4) of each shoulder groove 14 varies within a range of, for example, 2.5 mm to 5.5 mm. The median value of the width (W4) of the shoulder groove 14 is, for example, 3.0 mm to 5.0 mm. The width (W5) of the shoulder sipe 15 is, for example, 0.3 mm to 1.0 mm, and preferably 0.5 mm to 1.0 mm. The width (W4) may be approximately constant over the entire length of the shoulder groove 14, or may vary within the above range (the same applies to the shoulder sipe 15).

[0032] The depth of the shoulder groove 14 may be substantially constant over the entire length of the shoulder groove 14, or may vary along the length of the shoulder groove 14. For example, the bottom surface 14c of the shoulder groove 14 is inclined so as to become gradually deeper near the starting end 14a toward the ending end 14b, and the remaining 50 to 90% of the area is formed substantially flat. The bottom surface 15c of the shoulder sipe 15 is inclined so as to become gradually shallower toward the ending end 15b at a position overlapping with the ground contact edge E, and the depth of the shoulder sipe 15 may vary significantly at the border of the ground contact edge E.

[0033] As described above, the shoulder groove 14 and the shoulder sipe 15 extend beyond the ground contact edge E toward the outside in the tire width direction. The distances from the ground contact edge E to the ends 14b, 15b are different from each other, and the distance is longer in the shoulder sipe 15 than in the shoulder groove 14. In this embodiment, all the shoulder grooves 14 and shoulder sipes 15 are formed beyond the ground contact edge E, but grooves or sipes that do not exceed the ground contact edge E may exist within a range that does not impair the object of the present invention. Preferably, 90% or more, more preferably substantially all, of the shoulder grooves 14 and shoulder sipes 15 are formed beyond the ground contact edge E.

[0034] In this embodiment, the start end 14a of the shoulder groove 14 is located near the ground contact edge E and away from the main groove 10a. That is, the shoulder groove 14 does not communicate with the main groove 10a, and the start end 14a is present in the shoulder rib 11. On the other hand, the shoulder sipe 15 extends from the main groove 10a toward the outside in the tire width direction and communicates with the main groove 10a. In this case, the high rigidity of the shoulder rib 11 can be ensured while efficiently improving the drainage performance.

[0035] As described above, the shoulder groove 14 extends from a position away from the main groove 10a of the shoulder rib 11 to the outside in the tire width direction beyond the ground contact edge E. The shortest distance (L1) along the upper surface of the tread 2 from the tire equator CL to the terminal end 14b of the shoulder groove 14 is 1.10 to 1.20 times the shortest distance (L2) along the upper surface of the tread 2 from the tire equator CL to the ground contact edge E. The length of the shoulder groove 14, which is formed on the outside in the tire width direction from the ground contact edge E, is determined so that the ratio (L1 / L2) is 1.10 to 1.20.

[0036] Here, the upper surface of the tread 2 means a surface along the upper surface of the land portion hatched with dots in Fig. 1. In Fig. 1, the lengths (L1, L2, L3) are illustrated as linear distances in a plan view of the tread 2, but these are illustrated for convenience of explanation, and the lengths (L1, L2, L3) are distances along the upper surface of the tread 2.

[0037] If the length from the ground contact end E of the tread 2 to the terminal end 14b of the shoulder groove 14 is shortened and the ratio (L1 / L2) is less than 1.10, the shoulder groove 14 will not function sufficiently when the tire 1 wears, and the required wet grip performance will not be ensured. In addition, the shoulder groove 14 may disappear before the tire 1 shows signs of slipping. On the other hand, if the length from the ground contact end E to the terminal end 14b is lengthened and the ratio (L1 / L2) exceeds 1.20, the air resistance of the tire 1 will increase significantly. The ratio (L1 / L2) is more preferably 1.12 to 1.17.

[0038] As described above, the shoulder sipes 15 extend from the main groove 10a beyond the ground contact edge E toward the outside in the tire width direction. The shortest distance (L3) along the top surface of the tread 2 from the tire equator CL to the terminal end 15b of the shoulder sipe 15 is longer than the distance (L1) and is 1.20 to 1.35 times the distance (L2). The shoulder sipes 15 extend beyond the terminal end 14b of the shoulder groove 14 toward the outside in the tire width direction, and the length of the portion formed outside the ground contact edge E in the tire width direction is determined so that the ratio (L3 / L2) is 1.20 to 1.35.

[0039] If the length from the ground contact end E of the tread 2 to the terminal end 15b of the shoulder sipe 15 is shortened and the ratio (L3 / L2) becomes less than 1.20, the shoulder sipe 15 will not function sufficiently when the tire 1 wears, and the required wet grip performance cannot be ensured. Also, the shoulder sipe 15 may disappear before slip signs of the tire 1 appear. The shoulder sipe 15 has less effect on air resistance than the shoulder groove 14, but if the length from the ground contact end E to the terminal end 15b is lengthened and the ratio (L3 / L2) exceeds 1.35, the air resistance of the tire 1 will increase significantly.

[0040] The tire 1 is designed to reduce air resistance by shortening the shoulder grooves 14, and to secure wet grip performance that deteriorates as a result by lengthening the shoulder sipes 15, so that low air resistance and good wet grip performance can be achieved at the same time. For this reason, for example, when the distance (L3) is longer than the distance (L1) and the ratio (L3 / L2) is 1.20, it is preferable that the ratio (L1 / L2) is less than 1.20. As shown in the examples described later, low air resistance and good wet grip performance can be effectively achieved at the same time only when the ratio (L1 / L2) and the ratio (L3 / L2) are within the above ranges and the relationship of distance (L1)<distance (L3) is satisfied.

[0041] As described above, in order to reduce the air resistance of the tire 1 and improve the wet grip performance, the relationship between the length of the shoulder groove 14 and the shoulder sipe 15, particularly the relationship between the length of the portion extending from the ground contact end E of the tread 2 to the outside in the tire width direction, is important. The ratio (L1 / L2) may be 1.10 to 1.20, more preferably 1.12 to 1.17, but for example, when the ratio (L1 / L2) is 1.12 to 1.14, the ratio (L3 / L2) is preferably increased in the range of 1.20 to 1.35, and a suitable example is 1.26 to 1.35. On the other hand, when the ratio (L1 / L2) is 1.14 to 1.17, a suitable example of the ratio (L3 / L2) is 1.20 to 1.35 (however, the distance (L1)<the distance (L3)).

[0042] The number of shoulder grooves 14 aligned in the circumferential direction of the tire 1 is preferably 56 to 64, and more preferably 57 to 63. The relationship between the number of shoulder grooves 14 and the number of shoulder sipes 15 is not particularly limited, but in this embodiment, the number of shoulder grooves 14 and the number of shoulder sipes 15 are the same. The number of shoulder sipes 15 aligned in the circumferential direction of the tire is preferably 56 to 64, and more preferably 57 to 63, as in the case of the shoulder groove 14. If the number of shoulder grooves 14 and shoulder sipes 15 is within this range, low air resistance and good wet grip performance can be more effectively achieved at the same time.

[0043] In this embodiment, the shoulder land portion is exemplified by the shoulder rib 11 that is connected in the tire circumferential direction within the contact patch, but the shoulder land portion may be formed with a shoulder groove that crosses the land portion and connects to the main groove 10. In other words, the shoulder land portion may be formed in a block shape partitioned by the shoulder groove. EXAMPLES

[0044] The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

[0045] <Example 1> A test tire (tire size: 225 / 60R18 100H) having the tread pattern shown in Figures 1 and 2 was manufactured. Shoulder grooves and shoulder sipes were formed alternately at equal intervals in the shoulder rib along the tire circumferential direction. The number of grooves and sipes aligned in the tire circumferential direction was 60 each. The grooves and sipes were formed approximately parallel to each other, and had a gently curved planar shape that was convex toward the rear in the main tire rotation direction.

[0046] The sizes of the grooves and sipes are as follows. The ratios (L1 / L2) and (L3 / L2) are shown in Table 1. Distance (L1): 99mm Distance (L3): 110mm Distance (L2): 87mm Ratio (L1 / L2): 1.14 Ratio (L3 / L2): 1.26 Length(L4):37mm Length(L5):48mm Width (W4): Grooves having five different widths ranging from 2.5 mm to 4.0 mm were formed. The five types of grooves were arranged so that the width gradually increased along the tire circumferential direction. Fifteen sets of the five types of grooves were arranged along the tire circumferential direction. The median width (W4) was set to 3.3 mm. Width(W5):1mm

[0047] <Examples 2 to 5 and Comparative Examples 1 to 3> Test tires were produced in the same manner as in Example 1, except that the distances (L1) and (L3) were changed so that the ratio (L1 / L2) and the ratio (L3 / L2) were the values ​​shown in Table 1.

[0048] For each of the test tires of the Examples and Comparative Examples, the air resistance and wet grip performance were evaluated by the following methods.

[0049] [Air resistance evaluation] Each tire was mounted at the front tire position of a vehicle, and the air resistance of the tire was measured while the vehicle was running. The air resistance was calculated based on the fuel consumption when the vehicle was run a specified distance. The evaluation results are shown in Table 1. The evaluation results shown in Table 1 are relative values ​​with the evaluation result of the tire of Comparative Example 1 being 100, and the larger the value, the lower the air resistance. Vehicle: 3500cc gasoline vehicle (drive system: FF) Vehicle speed: 60km / h Tire installation conditions: Air pressure: 240kPa, Load: 656kgf (single wheel) Tire size: 225 / 60R18 100H (rim size 18X7.0J)

[0050] [Wet grip performance evaluation] The wet grip performance of each tire was evaluated under the test conditions stipulated in Regulation No. 117, 4.2 Testing method (b) using a trailer towed by a vehicle or a tire test vehicle of the Economic Commission for Europe of the United Nations (UNECE). The tire air pressure was 180 kPa and the load was 5.89 kN. The evaluation results are shown in Table 1. The evaluation results shown in Table 1 are relative values ​​with the evaluation result of the tire of Comparative Example 1 taken as 100, and the larger the value, the more excellent the wet grip performance.

[0051] [Table 1]

[0052] As shown in Table 1, all of the tires of the examples have reduced air resistance while having the same wet grip performance as the tire of Comparative Example 1. Also, all of the tires of the examples have excellent wet grip performance while having the same air resistance as the tire of Comparative Example 2. In other words, the tires of the examples can achieve both low air resistance and good wet grip performance. [Explanation of symbols]

[0053] 1 tire, 2 tread, 2A tread rubber, 3 sidewall, 3A sidewall rubber, 4 carcass, 5 belt, 6 inner liner, 10, 10a, 10b main groove, 11 shoulder rib, 12 center rib, 13 intermediate rib, 14 shoulder groove, 14a, 15a starting end, 14b, 15b ending end, 14c, 15c bottom surface, 15 shoulder sipe, E ground contact edge

Claims

1. A tire having a tread, the tread comprising: A main groove extending in a tire circumferential direction; A shoulder land portion formed on the outer side of the main groove in the tire width direction; A shoulder groove extending from the main groove side of the shoulder land portion beyond a tread ground contact edge toward an outer side in the tire width direction; a shoulder sipe extending from the main groove side of the shoulder land portion beyond a tread ground contact edge toward an outer side in the tire width direction; having A tire in which the shortest distance (L1) along the upper surface of the tread from the tire equator to an outer end of the shoulder groove in the tire width direction is 1.10 to 1.20 times the shortest distance (L2) along the upper surface of the tread from the tire equator to a ground-contact edge of the tread, and the shortest distance (L3) along the upper surface of the tread from the tire equator to an outer end of the shoulder sipe in the tire width direction is longer than the distance (L1) and is 1.20 to 1.35 times the distance (L2).

2. The tire according to claim 1, wherein the number of at least one of the shoulder grooves and the shoulder sipes aligned in the tire circumferential direction is 56 to 64.

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