JP5251179B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a one-ply structure carcass layer. More specifically, the present invention relates to a pneumatic tire having a high negative durability while maintaining good steering stability during high-speed driving under a condition in which a large negative camber is set. The present invention relates to a pneumatic tire that can improve the ride comfort.

  In recent years, the demand for weight reduction of pneumatic tires mounted on vehicles that are expected to run at high speed, such as sports cars, has become stricter. It is required to ensure the handling stability.

  On the other hand, a carcass layer having a one-ply structure is mounted between a pair of bead portions, a belt layer is disposed on the outer peripheral side of the carcass layer in the tread portion, and the carcass layer is disposed around each bead core disposed on each bead portion. The bead filler disposed on the bead core is sandwiched between the body portion and the winding portion of the carcass layer, and the lower portion of the belt layer is overlapped with the end portion of the belt layer. A pneumatic tire extended to the region has been proposed (see, for example, Patent Documents 1 to 3).

  A pneumatic tire having a carcass layer that extends to the lower region of the belt layer so as to overlap the end portion of the belt layer with a one-ply structure as described above is lightweight by using the carcass layer as one ply. In the sidewall portion, excellent steering stability can be exhibited by overlapping the main body portion and the winding portion of the carcass layer.

  However, a large negative camber is usually set in a vehicle that is assumed to be driven at high speed, and the wound portions on the left and right sides of the carcass layer overlap the end portions of the belt layer in a pneumatic tire that is mounted on such a vehicle. Thus, when the belt layer is extended to the lower region, the tire rigidity increases and the amount of deflection of the sidewall portion decreases, so stress concentrates around the end of the belt layer inside the vehicle, and high-speed durability is achieved. There is a problem that it leads to a decrease in performance and a deterioration in ride comfort.

In addition, a pneumatic tire having a carcass layer that extends to a lower region of the belt layer so that the winding portion overlaps with an end portion of the belt layer in a one-ply structure, for example, when continuous running in circuit running is performed, The steering stability tends to decrease with the generation of heat. For this reason, it is also demanded to suppress a change in performance of steering stability due to continuous running for a pneumatic tire that achieves both weight reduction and steering stability based on the above structure.
JP-A-5-238208 JP-A-6-16609 JP 2000-52709 A

An object of the present invention, under conditions that a large negative camber is set, while maintaining a good steering stability at high speeds, making it possible to improve the high speed durability and ride comfort, by further continuous running It is an object of the present invention to provide a pneumatic tire that can suppress a change in performance of steering stability .

In order to achieve the above object, the pneumatic tire of the present invention is a pneumatic tire in which the mounting direction of the front and back of the tire is specified when the vehicle is mounted, and the cord angle between the pair of bead portions with respect to the tire circumferential direction is 75 °. A carcass layer having a one-ply structure in a range of ˜90 ° is mounted, a belt layer is disposed on the outer periphery side of the carcass layer in the tread portion, and the carcass layer is disposed on the inner side of the tire around the bead core disposed in each bead portion. In a pneumatic tire in which the bead filler disposed on the bead core is sandwiched between the main body portion and the roll-up portion of the carcass layer,
Not more than 25mm height from the bead heel of the bead filler, with the cross-sectional area of the bead filler and 65 mm ² or less, the tanδ at 60 ° C. of the rubber composition constituting the bead filler in 0.20, The winding portion of the carcass layer on the vehicle outer side extends to a lower area of the belt layer so as to overlap the end portion of the belt layer on the vehicle outer side, while the carcass layer on the vehicle inner winding portion is defined as the belt layer. An asymmetric structure is formed so as not to overlap, and the winding portion of the carcass layer on the inner side of the vehicle is arranged at a position separated by 5 mm or more from the end portion of the belt layer on the inner side of the vehicle toward the bead portion ,
At least two kinds of cap tread rubber layers having different rubber compositions are arranged adjacent to each other in the tire width direction in the tread portion, and tan δ at 60 ° C. of the rubber composition constituting the at least two kinds of cap tread rubber layers. In the range of 0.10 to 0.50, and tan δ at 60 ° C. of the rubber composition constituting the cap tread rubber layer on the vehicle outer side is 60 ° C. of the rubber composition constituting the cap tread rubber layer on the vehicle inner side. The ratio (tan δH / tan δL) of the maximum value tan δH and the minimum value tan δL of tan δ at 60 ° C of the rubber composition constituting the at least two kinds of cap tread rubber layers is 1.05-1. .80 range,
The tread portion is provided with at least one main groove extending in the tire circumferential direction, and the groove area ratio GAo from the tread center to the vehicle outer contact area is greater than the groove area ratio GAi from the tread center to the vehicle inner contact area. An asymmetric tread pattern that is also smaller is formed, and the groove area ratio GA in the entire ground contact area is set in the range of 20% to 40%. The groove area ratio GAo in the ground contact area outside the vehicle and the groove area in the ground contact area inside the vehicle The difference (GAi−GAo) from the ratio GAi is in the range of 1% to 15% .

  In the present invention, in the pneumatic tire in which the mounting direction of the tire front and back when the vehicle is mounted is specified, the wound portion on the vehicle outer side of the carcass layer extends to the lower region of the belt layer so as to overlap the end portion on the vehicle outer side of the belt layer An asymmetric structure is formed in which the carcass layer's inner winding portion of the carcass layer is arranged so as not to overlap the belt layer, and the carcass layer's inner winding portion and the belt layer's inner end portion are separated from each other. By defining the amount, the flex zone on the inside of the vehicle is widened while ensuring the rigidity of the tire on the outside of the vehicle, so that even when a large negative camber is set, the steering stability at high speeds is maintained well. However, high-speed durability and ride comfort can be improved.

  In addition, the bead filler that is repeatedly deformed during rolling of the tire is lowered, the cross-sectional area thereof is reduced, and the tan δ at 60 ° C. of the rubber composition constituting the bead filler is reduced, thereby allowing continuous running on the circuit. The heat generation of the tire can be suppressed, and the performance change of the steering stability can be suppressed. Thereby, it is possible to maintain the initial steering stability for a long time in continuous running.

In the tread portion, at least two kinds of cap tread rubber layers having different rubber compositions are arranged adjacent to each other in the tire width direction, and tan δ at 60 ° C. of the rubber composition constituting the cap tread rubber layer on the vehicle outer side is determined. It is higher than tan δ at 60 ° C. of the rubber composition constituting the cap tread rubber layer on the inner side of the vehicle . Generally, when the tan δ at 60 ° C. of the rubber composition constituting the cap tread rubber layer is increased, the steering stability is improved, but the performance of the steering stability due to heat generation is likely to occur. On the other hand, as described above, tan δ is relatively high on the outside of the vehicle and tan δ is relatively low on the inside of the vehicle, thereby improving the steering stability and changing the performance of the steering stability by continuous running. Can be suppressed.

The ratio of the maximum value tan δH and the minimum value tan δH of tan δ at 60 ° C. (tan δH / tan δL) of the rubber composition constituting at least two types of cap tread rubber layers is in the range of 1.05-1.80 . Thereby, the effect which suppresses the performance change of the steering stability by continuous driving | running | working can be fully acquired, improving steering stability.

  It is preferable that the boundary between at least two types of cap tread rubber layers is disposed below the main groove extending in the tire circumferential direction at the tread portion. Thereby, generation | occurrence | production of the partial wear by the difference in a rubber composition can be suppressed.

Further, at least one main groove extending in the tire circumferential direction is provided in the tread portion, and the groove area ratio GAo from the tread center to the vehicle outer area is equal to the groove area ratio GAi from the tread center to the vehicle inner area. A smaller asymmetric tread pattern is formed . Thereby, the effect which suppresses the performance change of the steering stability by continuous driving | running | working can be fully acquired, improving steering stability.

In the asymmetric tread pattern, the groove area ratio GA in the entire ground contact area is in the range of 20% to 40%, and the groove area ratio GAo in the ground contact area outside the vehicle and the groove area ratio GAi in the ground contact area inside the vehicle are The difference (GAi−GAo) is in the range of 1% to 15% . Thereby, the effect which suppresses the performance change of the steering stability by continuous driving | running | working can be fully acquired, improving steering stability.

  In the present invention, the height of the bead filler from the bead heel is a height measured under the tire dimension measurement conditions defined in the standard on which the tire is based, and the height of the bead filler from the bead heel corresponding to the reference position of the rim diameter. This is the dimension in the tire radial direction up to the top. The tan δ at 60 ° C. is measured using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho) under the conditions of a temperature of 60 ° C., a frequency of 20 Hz, an initial strain of 10%, and a dynamic strain of ± 2%. The groove area ratio is the ratio (%) of the groove area in the ground contact area to the total area of the ground contact area measured under the tire static load radius measurement condition defined by the standard on which the tire is based.

  The present invention can be applied to various types of pneumatic tires. However, when the present invention is applied to a pneumatic tire having a tire size having a flatness ratio of 50% or less with a narrow flex zone, a remarkable effect can be obtained. In particular, when applied to a pneumatic tire mounted on a vehicle having a camber angle of −0.5 ° to −4.0 °, a remarkable effect can be obtained.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. This pneumatic tire is a tire in which the mounting direction of the tire front and back when the vehicle is mounted is designated. In FIG. 1, IN is the inside of the vehicle when the vehicle is mounted, and OUT is the outside of the vehicle when the vehicle is mounted.

  In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. As shown in FIG. 1, a single carcass layer 4 composed of a plurality of aligned carcass cords is mounted between a pair of bead portions 3 and 3. As the carcass cord, an organic fiber cord made of rayon, polyester, nylon, aromatic polyamide or the like is preferably used. The cord angle of the carcass layer 4 with respect to the tire circumferential direction is set in the range of 75 ° to 90 °, preferably in the range of 80 ° to 87 °. The cord angle of the carcass layer 4 with respect to the tire circumferential direction is, for example, a high angle when the load factor is low, and a low angle when the load factor is high. The performance can be maintained. The carcass layer 4 is wound up around the bead core 5 from the inside of the tire to the outside. That is, the carcass layer 4 includes a main body portion 4a and a winding portion 4b with the bead core 5 as a boundary.

  In each bead portion 3, a bead filler 6 made of a rubber composition having a high hardness is disposed on the outer periphery of the bead core 5, and the bead filler 6 is sandwiched between the main body portion 4 a and the winding portion 4 b of the carcass layer 4. . In order to ensure the rigidity of the bead portion 3, a reinforcement layer including a reinforcement cord such as an organic fiber cord or a steel cord may be embedded in the bead portion 3.

  On the other hand, a plurality of belt layers 8 including reinforcing cords inclined with respect to the tire circumferential direction are disposed on the outer peripheral side of the carcass layer 4 in the tread portion 1. Further, a belt cover layer 9 including reinforcing cords oriented in the tire circumferential direction is disposed on the outer peripheral side of the belt layer 8. The carcass layer 4 on the outer side of the vehicle 4 is extended to the lower side of the belt layer 8 so as to overlap the end 8o on the outer side of the belt layer 8, while the carcass layer 8 is wound on the inner side of the vehicle 4bi. Is formed with an asymmetric structure that terminates at a position that does not overlap the belt layer 8. More specifically, the winding portion 4bi on the vehicle inner side of the carcass layer 4 is separated from the end portion 8i on the inner side of the belt layer 8 toward the bead portion, and the separation amount W is set to 5 mm or more. This separation amount W is the length from the vehicle inner end portion 8i of the belt layer 8 to the vehicle inner winding portion 4bi of the carcass layer 4 measured along the main body portion 4a of the carcass layer 4 in the tire meridian cross section. .

  Thus, in the pneumatic tire in which the mounting direction of the tire front and back when the vehicle is mounted is specified, the belt layer 8 so that the vehicle outer winding portion 4bo of the carcass layer 4 overlaps the vehicle outer end portion 8o of the belt layer 8. The carcass layer 4 has an asymmetrical structure in which the vehicle inner winding portion 4bi is disposed so as not to overlap the belt layer 8, and the carcass layer 4 inner winding portion 4bi and the belt layer. By defining the distance W between the vehicle inner end 8i and the vehicle inner end portion 8i, the vehicle outer flex zone is widened while ensuring the vehicle outer tire rigidity, so even under conditions where a large negative camber is set, High-speed durability and ride comfort can be improved while maintaining good steering stability during high-speed driving. For example, when a high-speed durability test with a camber is performed, the durability level is suppressed by suppressing the separation between the edge of the belt layer 8 and the carcass layer 4 and between the carcass layer 4 and the side rubber adjacent thereto. Can be increased. In addition, with regard to steering stability during high-speed traveling, particularly high-speed lane change performance can be improved.

  Here, if the separation distance W between the vehicle inner winding portion 4bi of the carcass layer 4 and the vehicle inner end portion 8i of the belt layer 8 is less than 5 mm, the durability deteriorates due to stress concentration, so the separation amount W is 5 mm. It is necessary to do more. In order to form a winding structure, the winding portion 4bi on the vehicle inner side of the carcass layer 4 preferably has a height TH of 10 mm or more from the bead heel. However, in order to exhibit excellent steering stability, the height from the bead heel is high. It is preferable that TH be 50% or more of the tire cross-section height SH.

In the pneumatic tire, the height FH of the bead filler 6 from the bead heel is set to 25 mm or less, the cross-sectional area of the bead filler 6 in the tire meridian section is set to 65 mm ² or less, and the rubber composition constituting the bead filler 6 Tan δ at 60 ° C. is set to 0.20 or less.

  In a pneumatic tire, the deformation of the bead filler 6 is repeated at the time of rolling. When the amount of heat generated due to the bead filler 6 increases thereby, a change in performance of steering stability becomes remarkable. Therefore, by lowering the bead filler 6 and reducing its cross-sectional area, the tan δ at 60 ° C. of the rubber composition constituting the bead filler 6 is reduced to suppress the heat generation of the tire due to continuous running on the circuit. , The performance change of the steering stability can be suppressed. As a result, it is possible to maintain the initial steering stability for a long time in continuous running.

  Here, if the height FH of the bead filler 6 is more than 25 mm, the effect of suppressing the performance change of the steering stability becomes insufficient. The lower limit value of the height FH of the bead filler 6 is preferably 10 mm.

Similarly, if the cross-sectional area of the bead filler 6 exceeds 65 mm ² , the effect of suppressing the change in performance of the steering stability becomes insufficient. The lower limit value of the cross-sectional area of the bead filler 6 is preferably 15 mm ² .

  Further, if the tan δ at 60 ° C. of the rubber composition constituting the bead filler 6 is more than 0.20, the effect of suppressing the performance change of the steering stability becomes insufficient. The lower limit value of tan δ at 60 ° C. of the rubber composition constituting the bead filler 6 is preferably 0.03.

  In the tire in which the tire front and back mounting directions are specified as described above, as shown in FIG. 1, two types of cap tread rubber layers 1A and 1B having different rubber compositions are adjacent to the tread portion 1 in the tire width direction. Is arranged. The tan δ at 60 ° C. of the rubber composition constituting the cap tread rubber layer 1A on the vehicle outer side is higher than the tan δ at 60 ° C. of the rubber composition constituting the cap tread rubber layer 1B on the vehicle inner side. Yes. By providing a difference in the tan δ of the rubber composition of the cap tread rubber layers 1A and 1B, it is possible to suppress the heat generation in the tread portion 1 and to suppress the change in performance of the steering stability while improving the steering stability. become. The range of tan δ at 60 ° C. of the rubber composition constituting the cap tread rubber layer is preferably 0.10 to 0.50.

  The ratio of tan δH at 60 ° C. of the rubber composition constituting the cap tread rubber layer 1A to tan δL at 60 ° C. of the rubber composition constituting the cap tread rubber layer 1B (tan δH / tan δL) is 1.05-1.80. More preferably, it is set in the range of 1.10 to 1.50. If this ratio (tan δH / tan δL) is too small, the effect of suppressing the change in performance of steering stability is reduced, and conversely, if it is too large, the originally required grip force cannot be obtained. Note that the boundary between the cap tread rubber layers 1A and 1B is preferably disposed below the main groove 60 extending in the tire circumferential direction in the tread portion 1. Thereby, generation | occurrence | production of the partial wear by the difference in a rubber composition can be suppressed.

  In this embodiment, two types of cap tread rubber layers 1A and 1B having different rubber compositions are arranged in the tread portion 1, but two or more types of cap tread rubber layers are arranged adjacent to each other in the tire width direction. be able to.

  FIG. 2 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention. In FIG. 2, CL is a tread center. As shown in FIG. 2, a plurality of main grooves 60 extending in the tire circumferential direction are formed in the tread portion 1, and a plurality of land portions 10, 20, 30 are formed by the main grooves 60 from the vehicle outer side toward the vehicle inner side. , 40, 50 are partitioned. The land portion 10 located on the outermost side of the vehicle has a narrow groove 11 extending in the tire circumferential direction, a plurality of lateral grooves 12 extending in the tire width direction on the tread shoulder side from the narrow groove 11, and at least the tread than the narrow groove 11. A plurality of narrow grooves 13 extending in the tire width direction on the center side are formed. The land portion 20 is formed with narrow grooves 21 extending in the tire circumferential direction and a plurality of cutout grooves 22 extending in the tire width direction. The land portion 30 is formed with a plurality of curved grooves 31 extending while being curved in the tire circumferential direction, and a plurality of cutout grooves 32 extending in the tire width direction. The land portion 40 has a tire circumferential direction. A plurality of curved grooves 41 extending while being curved are formed. A plurality of lateral grooves 51 extending in the tire width direction and a plurality of narrow grooves 52 extending in the tire width direction are formed between the lateral grooves 51 in the land portion 50 located on the innermost side of the vehicle.

  In the pneumatic tire described above, at least one main groove 60 extending in the tire circumferential direction is formed in the tread portion 1, and in the entire ground contact region defined by the ground contact width TCW, in the ground contact region outside the vehicle from the tread center CL. Has an asymmetric tread pattern in which the groove area ratio GAo is smaller than the groove area ratio GAi in the ground contact region inside the vehicle from the tread center CL. Thereby, the effect which suppresses the performance change of the steering stability by continuous driving | running | working can be fully acquired, improving steering stability.

  Here, the groove area ratio GA in the entire ground contact area ranges from 20% to 40%, and the groove area ratio GAo in the ground contact area outside the vehicle from the tread center CL and the groove in the ground contact area inside the vehicle from the tread center CL. The difference from the area ratio GAi (GAi−GAo) is preferably in the range of 1% to 15%, more preferably in the range of 2% to 13%. If this difference (GAi−GAo) is too small, the effect of suppressing the change in performance of the steering stability is reduced. On the other hand, if it is too large, the steering stability is lowered due to insufficient block rigidity.

With a tire size of 235 / 40R18, a carcass layer having a one-ply structure with a cord angle with respect to the tire circumferential direction of 85 ° is mounted between a pair of bead portions, and a belt layer is disposed on the outer peripheral side of the carcass layer in the tread portion, In a pneumatic tire in which the carcass layer is wound around the bead core disposed on each bead portion from the inside to the outside of the tire, and the bead filler disposed on the bead core is sandwiched between the main body portion and the wound portion of the carcass layer. The height of the filler from the bead heel, the cross-sectional area of the bead filler, tan δ of the rubber composition constituting the bead filler at 60 ° C., the position of the carcass layer on the vehicle outer side and the vehicle inner side, the vehicle outer side and the vehicle inner cap Tan δ at 60 ° C. of the rubber composition constituting the tread rubber layer, groove surface on the vehicle outer side and vehicle inner side Comparative Example 1-5 the set as a percentage in Table 1, Reference Examples 1-5 and Example 1 tire was produced, respectively. Regarding the positions of the carcass layer on the vehicle outer side and on the vehicle inner side, the plus value means the amount of overlap with the end of the belt layer, and the minus value means the amount of separation from the end of the belt layer. For the rolled-up portion inside the carcass layer, the ratio of the height TH from the bead heel and the height TH to the tire cross-section height SH (TH / SH × 100%) is displayed.

  With respect to these test tires, performance changes in high speed durability, high speed lane change performance, riding comfort, and steering stability were evaluated by the following test methods, and the results are also shown in Table 1.

High speed durability:
The test tire is mounted on a drum testing machine, the load is 0.85 times the maximum load capacity, the air pressure is 250 kPa, the camber angle is -2.5 °, and the speed is from 200 km / h to 10 km / h every 10 minutes. Step by step, and the distance traveled until the tire broke down. The evaluation results are shown as an index with Comparative Example 1 as 100. It means that high speed durability is excellent, so that this index value is large.

High-speed lane change performance:
The test tire is fitted to a wheel with a rim size of 18 x 8 J and mounted on a vehicle with a displacement of 4000 cc class (camber angle: -2.5 °). A running test is conducted by a test driver under the condition of an air pressure of 250 kPa. Sensory evaluation was performed on the lane change. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the high-speed lane change performance.

Ride comfort:
The test tire is fitted to a wheel with a rim size of 18 x 8 J and mounted on a vehicle with a displacement of 4000 cc class (camber angle: -2.5 °), and a running test is conducted by a test driver under the condition of an air pressure of 250 kPa. A sensory evaluation was performed on the comfort. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the ride comfort.

Steering stability performance change:
The test tire is fitted to a wheel with a rim size of 18 x 8 J and mounted on a vehicle with a displacement of 4000 cc (camber angle: -2.5 °). The test driver runs continuously for 200 km under the condition of air pressure of 250 kPa. The sensory evaluation was performed on the change between the handling stability at the beginning of driving and the driving stability at the end of driving. The evaluation results are indicated by an index with a pass level of 100. A larger index value means less performance change.

As shown in Table 1, the tires of Example 1, in comparison with the Comparative Example 1, under conditions that a large negative camber is set, while maintaining a good steering stability during high speed running, excellent It exhibited high-speed durability and ride comfort, and there was little change in performance of steering stability due to continuous running. On the other hand, Comparative Examples 2 to 5 could not obtain a sufficient improvement effect with respect to handling stability, high speed durability and riding comfort during high speed running.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is a top view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 1A, 1B Cap tread rubber layer 2 Side wall part 3 Bead part 4 Carcass layer 4a Body part 4b, 4bi, 4bo Roll-up part 5 Bead core 6 Bead filler 8 Belt layer 8i, 8o End part of belt layer 9 Belt cover layer 60 Main groove

Claims (4)

A pneumatic tire in which a tire front and back mounting direction is specified when the vehicle is mounted, and a carcass layer having a one-ply structure in which a cord angle with respect to the tire circumferential direction is in a range of 75 ° to 90 ° between a pair of bead portions. The belt layer is arranged on the outer peripheral side of the carcass layer in the tread portion, the carcass layer is wound up around the bead core arranged in each bead portion from the inside of the tire to the outside, and the bead filler arranged on the bead core is provided. In the pneumatic tire that is sandwiched between the main body portion and the winding portion of the carcass layer,
Not more than 25mm height from the bead heel of the bead filler, with the cross-sectional area of the bead filler and 65 mm ² or less, the tanδ at 60 ° C. of the rubber composition constituting the bead filler in 0.20, The winding portion of the carcass layer on the vehicle outer side extends to a lower area of the belt layer so as to overlap the end portion of the belt layer on the vehicle outer side, while the carcass layer on the vehicle inner winding portion is defined as the belt layer. An asymmetric structure is formed so as not to overlap, and the winding portion of the carcass layer on the inner side of the vehicle is arranged at a position separated by 5 mm or more from the end portion of the belt layer on the inner side of the vehicle toward the bead portion ,
At least two kinds of cap tread rubber layers having different rubber compositions are arranged adjacent to each other in the tire width direction in the tread portion, and tan δ at 60 ° C. of the rubber composition constituting the at least two kinds of cap tread rubber layers. In the range of 0.10 to 0.50, and tan δ at 60 ° C. of the rubber composition constituting the cap tread rubber layer on the vehicle outer side is 60 ° C. of the rubber composition constituting the cap tread rubber layer on the vehicle inner side. The ratio (tan δH / tan δL) of the maximum value tan δH and the minimum value tan δL of tan δ at 60 ° C of the rubber composition constituting the at least two kinds of cap tread rubber layers is 1.05-1. .80 range,
The tread portion is provided with at least one main groove extending in the tire circumferential direction, and the groove area ratio GAo from the tread center to the vehicle outer contact area is greater than the groove area ratio GAi from the tread center to the vehicle inner contact area. An asymmetric tread pattern that is also smaller is formed, and the groove area ratio GA in the entire ground contact area is set in the range of 20% to 40%. The groove area ratio GAo in the ground contact area outside the vehicle and the groove area in the ground contact area inside the vehicle A pneumatic tire in which the difference from the ratio GAi (GAi-GAo) is in the range of 1% to 15% . The pneumatic tire according to claim 1 , wherein a boundary between the at least two types of cap tread rubber layers is disposed under a main groove extending in a tire circumferential direction at a tread portion. The pneumatic tire according to any one of claims 1 to 2 aspect ratio has a tire size of 50% or less. The pneumatic tire according to any one of claims 1 to 3 , which is mounted on a vehicle having a camber angle of -0.5 ° to -4.0 °.

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