JP2016016823A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to reduce air column tube resonance sound thereby reducing noise during travelling.SOLUTION: A pneumatic tire includes plural major grooves 12, in which groove positions and groove widths are symmetrically provided with respect to a tire equator plane CL, and plural ribs 14, 16, 16 formed between the major grooves in a tread part 10. In the pneumatic tire, ground planes of the plural ribs are bulged in a tire radial direction outer side Ko with respect to a reference contour line L of the tread part, and bulging amounts H, H1, H2 of respective ribs 14, 16, 16 with respect to the reference contour line L are so made as to be different from one another.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  In the tread portion of a pneumatic tire, a plurality of main grooves extending in the tire circumferential direction are generally provided so that the groove position and the groove width are symmetrical with respect to the tire equatorial plane. In such a tire, the pipe resonance frequency coincides between the pair of main grooves located symmetrically with respect to the tire equatorial plane, so that there is a concern that the noise performance deteriorates in a high frequency region near 1 kHz. . In particular, in recent years, there are more tread patterns based on ribs mainly composed of ribs extending in the tire circumferential direction than block patterns to achieve both low fuel consumption and steering stability, and there are no transverse grooves across the ribs. Therefore, the problem of noise during traveling due to air column resonance is more likely to become obvious.

  In Patent Document 1, in order to propose a noise during traveling, a ground contact surface of an intermediate land portion formed between a central land portion and a shoulder land portion is assumed, and a virtual surface including a ground contact surface of the central land portion and the shoulder land portion is included. It is disclosed that the ground contact length of the intermediate land portion is shorter than the contact lengths of the central land portion and the shoulder land portion, which is lower than the line.

  On the other hand, in Patent Document 2, in order to improve the ground contact property in the entire tire width direction of the tread part and improve the steering stability, the ground contact surfaces of the central land part and the intermediate land part are defined with respect to the reference contour line of the tread part. It is disclosed that a predetermined amount is bulged outwardly in the tire radial direction and that the bulge amount is larger in the central land portion than in the intermediate land portion.

  Further, in Patent Document 3, in order to improve steering stability during cornering, the ground contact surface of the rib formed between the main grooves is outside the tire radial direction with respect to the outer contour line passing through the ground contact surface of the shoulder rib. It is disclosed that the bulging vertices of the ribs are displaced inward when the vehicle is mounted with respect to the center line of the ribs.

Japanese Patent Application Laid-Open No. 08-091015 JP 2013-189121 A JP 2005-263180 A

  In the configurations disclosed in Patent Documents 1 to 3, since the tube lengths formed between the main grooves located symmetrically with respect to the tire equatorial plane and the road surface at the time of tire contact are the same, the frequency of air column resonance Therefore, the effect of suppressing noise in a high frequency range cannot be obtained.

  An object of the present invention is to provide a pneumatic tire that can reduce air columnar resonance noise and reduce noise during traveling.

  The pneumatic tire according to the first embodiment includes a plurality of main grooves extending in the tire circumferential direction in which groove positions and groove widths are provided symmetrically with respect to the tire equatorial plane, and ribs formed between the main grooves. In the pneumatic tire having a plurality of ribs that are not provided with a transverse groove that crosses the ribs, and the tread portion includes all of the plurality of ribs formed between the main grooves or one of the plurality of ribs. The ribs other than the ribs of the ribs have a ground contact surface bulging outward in the tire radial direction with respect to the reference contour line of the tread portion, and the bulge amounts of the ribs with respect to the reference contour line are different from each other. Is.

  The pneumatic tire according to the second embodiment includes a pair of center main grooves extending in the tire circumferential direction in which a groove position and a groove width are provided symmetrically with respect to the tire equatorial plane, and an outer side in the tire width direction of the center main groove. A pair of shoulder main grooves extending in the tire circumferential direction provided symmetrically with respect to the tire equatorial plane, a center rib formed between the pair of center main grooves, and the center main In a pneumatic tire provided in a tread portion, a pair of intermediate ribs formed between a groove and the shoulder main groove, and a pair of shoulder ribs formed outside the pair of shoulder main grooves in the tire width direction, Of the pair of intermediate ribs, at least the outer intermediate rib and the central rib when mounted on the vehicle have a ground contact surface that bulges outward in the tire radial direction with respect to the reference contour line of the tread portion, The amount of bulging from the reference contour is larger at the central rib than the outer intermediate rib when mounted on the vehicle, and larger at the outer intermediate rib when mounted on the vehicle than the inner intermediate rib when mounted on the vehicle. .

  According to the present embodiment, the ribs formed between the main grooves have different contact lengths at the time of tire contact with each other, so that the frequency band of air column resonance at the time of tire traveling can be dispersed, and air column resonance Sound can be reduced. In particular, according to the second embodiment, the contact length of the central rib at the time of tire contact can be increased to improve the handling stability in the low load range, and the contact length of the outer intermediate rib can be increased when the vehicle is mounted. As a result, the steering stability in a high load range can be improved, and therefore the steering stability can be improved while reducing the air column resonance noise.

1 is a cross-sectional view in the width direction of a tread portion of a pneumatic tire according to an embodiment. The principal part expanded sectional view of the tread part of FIG. The figure which shows the contact shape of the pneumatic tire. Sectional drawing of the width direction of the tread part of the pneumatic tire which concerns on other embodiment. The principal part expanded sectional view of the tread part of FIG. The figure which shows the contact shape of the pneumatic tire of a comparative example.

  FIG. 1 is a cross-sectional view along a tire width direction W (meridian direction) showing a tread portion 10 of a pneumatic tire according to an embodiment. This tire is a pneumatic radical tire for passenger cars, and includes a tread portion 10 and a pair of left and right bead portions (not shown) and sidewall portions, and the tread portion 10 is a tire of left and right sidewall portions 1 and 1. The outer end portions in the radial direction K are provided so as to be connected to each other. In the figure, CL indicates the tire equator plane and corresponds to the center in the width direction W of the tire.

  A carcass 2 composed of at least one carcass ply extending across a pair of bead portions is embedded in the pneumatic tire. The carcass 2 extends from the tread portion 10 through the sidewall portion 1, and both end portions are locked at the bead portion. A belt 3 is provided on the outer peripheral side of the carcass 2 in the tread portion 10. The belt 3 is composed of a plurality of belt plies formed by inclining a belt cord at a shallow angle with respect to the tire circumferential direction. In this example, the belt 3 is composed of two belt plies. On the outer peripheral side of the belt 3, a belt reinforcing layer 4 in which fiber cords are arranged along the tire circumferential direction is provided.

  A tread rubber 5 is provided on the outer peripheral side of the belt 3 (specifically, the outer peripheral side of the belt reinforcing layer 4), and the tread rubber 5 forms a surface of a tread portion 10 that constitutes a tire contact surface.

  The surface of the tread portion 10 is provided with a plurality of (four in this example) straight main grooves 12 extending in the tire circumferential direction in which groove positions and groove widths are provided symmetrically with respect to the tire equatorial plane CL. Yes. Specifically, the main groove 12 includes a pair of center main grooves 12A and 12A in which the groove position and the groove width are provided symmetrically with the tire equatorial plane CL on both sides of the tire equatorial plane CL, and a pair of center main grooves. 12A and 12A are composed of a pair of shoulder main grooves 12B and 12B which are provided symmetrically with respect to the tire equatorial plane CL on the tire width direction outer side Wo. Here, the groove position is the position of the main groove 12 in the tire width direction W with respect to the tire equatorial plane CL, and the groove width is the width of each main groove 12. Therefore, the pair of center main grooves 12A and 12A have the same groove width and are provided at the same distance from the tire equatorial plane CL, and the pair of shoulder main grooves 12B and 12B have the same groove width. And the distance from the tire equatorial plane CL is provided at the same position. The tire width direction outer side Wo refers to a side away from the tire equatorial plane CL in the tire width direction W.

  By the four main grooves 12, the tread portion 10 is formed between the center rib 14 formed between the pair of left and right center main grooves 12A and 12A, and between the center main groove 12A and the shoulder main groove 12B. A pair of left and right intermediate ribs 16, 16 and a pair of left and right shoulder ribs 18, 18 formed on the outer side Wo in the tire width direction of the pair of left and right shoulder main grooves 12B, 12B are provided.

  As shown in FIG. 3, each rib 14, 16, 18 is not provided with a transverse groove that crosses the rib. That is, the ribs 14, 16, and 18 are not provided with lateral grooves that extend in a direction intersecting the main groove 12 and communicate with both sides of the ribs. It is not divided in the direction C, and is formed continuously over the entire circumference in the tire circumferential direction C.

  As shown in FIGS. 1 and 2, the central rib 14 and the pair of intermediate ribs 16 and 16 bulge outward in the tire radial direction Ko with respect to the reference contour line L of the tread portion 10, and are formed in a bowl shape. Has been. On the other hand, the shoulder ribs 18 and 18 do not bulge from the reference contour L, that is, the ground contact surface 19 of the shoulder rib 18 is on the reference contour L.

  Here, the reference contour line L is a curve that serves as a reference for defining a tread surface in a cross section along the tire width direction W, and is generally a tire tread that is formed by a curve in which a plurality of arcs are connected at a contact point having a common tangent line. It can also be identified with the design profile. Specifically, the reference contour line L is a curve composed of one or a plurality of arcs smoothly passing through the open ends of the main grooves 12 (edges of the ribs 14, 16, 18), for example, When the open ends of all the main grooves 12 are on a single arc, the arc becomes the reference contour L. However, since the open ends of all the main grooves 12 are not usually on a single arc, the reference contour line L is formed from a plurality of arcs and is defined as follows. As shown in FIG. 2, in the central rib 14, the edges a, b, c of the intermediate rib 16 adjacent to both edges a, b of the rib 14 and the center main groove 12A are obtained. Among the arcs passing through and the points a, b, d, let the arc having a large curvature radius be the reference contour line L. This is because the central rib 14 basically has a large radius of curvature, and thus an arc having a large radius of curvature is generally closer to the design profile of the central rib 14. In the intermediate rib 16, an arc passing through three points b, d, e between both edges d, e of the rib 16 and the edge b of the adjacent central rib 14 across the center main groove 12 </ b> A is defined as a reference contour L. . Since the design profile is formed by an arc having a smaller curvature radius as the distance from the tire equatorial plane CL increases, the design profile is defined by defining the reference contour line L at the intermediate rib 16 as an arc passing through the edge f of the shoulder rib 18 adjacent to the outside. May be smaller than the arc. Therefore, it defines using the edge b of the center rib 14 adjacent inside.

  The central rib 14 and the pair of intermediate ribs 16, 16 bulge outwardly in the tire radial direction Ko from the reference contour line L so that the central portion in the width direction W protrudes most. Thereby, the ground contact surfaces 14A and 16A of the center rib 14 and the intermediate rib 16 have an arcuate cross-sectional shape in which the vertices 14A1 and 16A1 are located at the center in the tire width direction W.

  The bulge amounts of the central rib 14 and the pair of intermediate ribs 16 and 16 with respect to the reference contour line L are different from each other. Specifically, the pneumatic tire according to the present embodiment is a tire in which a surface that is on the inside and a surface that is on the outside when the vehicle is mounted is determined. In FIG. The side that is the outer side at the time of mounting is indicated as “the vehicle outer side”. The bulging amount of the central rib 14 from the reference contour L (that is, the distance from the apex 14A1 of the central rib 14 to the reference contour L) is H, and the reference contour L of the intermediate rib 16-1 outside when the vehicle is mounted. Bulge amount from the reference contour line L of the intermediate rib 16-2 on the inner side when the vehicle is mounted is defined as H1 (ie, the distance from the vertex 16A1-1 of the intermediate rib 16-1 to the reference contour line L). The amount of protrusion (that is, the distance from the vertex 16A1-2 of the intermediate rib 16-2 to the reference contour line L) is H2. At this time, it is formed so that H> H1> H2.

  Although the value of these bulging amounts is not particularly limited, the bulging amount H at the central rib 14 is preferably 0.5 to 1.5 mm. The bulging amounts H1 and H2 at the intermediate ribs 16-1 and 16-2 can be appropriately set so as to satisfy the relationship of H> H1> H2.

  The bulging amount of the reference contour line L and each of the ribs 14 and 16 is that in a normal state of no load in which a pneumatic tire is mounted on a regular rim and filled with a regular internal pressure. It is obtained by measuring with a shape measuring device. The regular rim is “standard rim” in JATMA standard, “Design Rim” in TRA standard, or “Measuring Rim” in ETRTO standard. The normal internal pressure is “maximum air pressure” in JATMA standard, “maximum value” described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, or “INFLATION PRESSURE” in ETRTO standard.

  According to the present embodiment, in each of the ribs 14, 16-1 and 16-2 sandwiched between the main grooves 12, the ground contact surfaces 14 </ b> A, 16 </ b> A and 16 </ b> A are bulged outward in the tire radial direction as described above. Since the ribs are formed with different bulge amounts, the contact lengths in the circumferential direction C at the time of tire contact are different between the ribs 14, 16-1, and 16-2 as shown in FIG. As a result, the frequency band of air column resonance at the time of running of the tire can be dispersed, and air column resonance noise can be reduced.

  In detail, in the tire of the comparative example in which the ground contact surfaces of the ribs 14, 16-1 and 16-2 are not bulged, as shown in FIG. 6, the grounding of the left and right intermediate ribs 16-1 and 16-2 is performed. The lengths Sm1 and Sm2 are the same (Sm1 = Sm2). Therefore, in the pair of center main grooves 12A and 12A, the tube lengths formed with the road surface at the time of tire contact are equal, and the tube resonance frequencies coincide. The pair of shoulder main grooves 12B and 12B also have the same tube length formed between the road surface and the road surface, and the tube resonance frequencies match. Therefore, it causes noise due to air columnar resonance.

  On the other hand, in this embodiment, as shown in FIG. 3, the ground contact length Sc of the central rib 14 is the longest because the ribs 14, 16-1, 16-2 are bulged as described above. Next, the contact length Sm1 of the outer intermediate rib 16-1 when mounted on the vehicle, the contact length Sm2 of the inner intermediate rib 16-2 when mounted on the vehicle, and then the contact length Ss of the shoulder ribs 18 and 18 (Sc>). Sm1> Sm2> Ss). For this reason, the center main grooves 12A and 12A in the left and right symmetrical positions have different tube lengths from the road surface at the time of tire contact, so that the pipe resonance frequencies coincide between the pair of center main grooves 12A and 12A. It shifts without doing. The shoulder main grooves 12B and 12B at the left and right symmetrical positions also have different tube lengths, so that the tube resonance frequencies are not matched between the pair of shoulder main grooves 12B and 12B. Therefore, the frequency band of the air column resonance at the time of running the tire can be dispersed, and noise due to the air column resonance sound in the high frequency region can be reduced.

  According to the present embodiment, since the contact length Sc of the central rib 14 at the time of tire contact is made the longest, the steering stability in a low load region can be improved. Further, by increasing the ground contact length Sm1 of the intermediate rib 16-1 on the outside when the vehicle is likely to be loaded in the high load region, the steering stability in the high load region can be improved. Therefore, it is possible to effectively improve steering stability while reducing air columnar resonance noise.

  In the above embodiment, the intermediate rib 16-2 on the inner side when the vehicle is mounted is also bulged outward in the tire radial direction Ko with respect to the reference contour line L. It is not necessary to bulge from the contour line L (that is, H2 = 0 mm). Since the contact lengths of the ribs 14, 16-1, and 16-2 can be made different from each other without bulging, the same effect can be obtained.

  In the above embodiment, for the bulging amounts H, H1, and H2 of the ribs 14, 16-1, and 16-2, the ratio of the bulging amount is set to a value that is nearly equal, and the ribs 14, 16-1, and 16 For example, H1 may be set to 0.4 to 0.6 times H and H2 may be set to 0 to 0.3 times H in order to make the ratio of the contact length of -2 close to equal. By setting the ratio of the contact lengths to a value close to equality, the frequency band of air column resonance can be evenly distributed, and the effect of reducing air column resonance noise can be enhanced.

  Further, for example, when the groove width wa of the center main groove 12A is sufficiently smaller than the groove width wb of the shoulder main groove 12B, if the difference in bulging amount between the center rib 14 and the intermediate rib 16 is small, the center main groove The tube resonance frequency between 12A and the shoulder main groove 12B becomes close, and the noise reduction effect may be reduced. Therefore, for example, when the groove width wa of the center main groove 12A is ½ or less (wa / wb ≦ 0.5) of the groove width wb of the shoulder main groove 12B, the intermediate rib 16-1 on the outer side when the vehicle is mounted. It is preferable to set the bulging amount H1 at 1/3 or less (H1 / H ≦ 1/3) of the bulging amount H at the central rib 14. Thus, by setting a large difference in the amount of bulging between the central rib 14 and the intermediate rib 16, the difference in tube resonance frequency between the center main groove 12A and the shoulder main groove 12B is increased, and the noise reduction effect is enhanced. be able to.

  In the above embodiment, the case where the central rib 14, the pair of intermediate ribs 16, 16 and the pair of shoulder ribs 18, 18 are provided by the four main grooves 12 has been described, but ribs formed between the main grooves ( That is, the number of main grooves is not limited to four as long as it has a plurality of ribs sandwiched between main grooves, and may be three or five, for example. Even in the case of three or five main grooves, as in the above-described embodiment, all of the plurality of ribs formed between the main grooves or all other ribs except one rib are used as the ground plane. With respect to the reference contour line of the tread portion, it can bulge outward in the tire radial direction, and the bulge amounts of the ribs with respect to the reference contour line can be set to be different from each other, and a noise reduction effect can be obtained.

  When five main grooves are provided, as shown in FIGS. 4 and 5, one main groove 12C is provided on the tire equatorial plane CL, and the central rib 14 is divided into left and right by the main groove 12C. You may comprise as follows. In this case, the divided central ribs 14-1 and 14-2 can be handled in the same manner as the central rib 14 of the embodiment shown in FIG. For example, the bulging amount H of the central ribs 14-1 and 14-2 from the reference contour L (that is, from the vertex (highest point) 14A1 of the divided central ribs 14-1 and 14-2 to the reference contour L) The distance) may be set so as to satisfy H> H1> H2.

  In the above embodiment, the case where the ribs 14, 16, and 18 are not provided with the lateral grooves has been described. However, the ribs 14, 16, and 18 may be provided side by side in the tire circumferential direction so long as they do not cross the ribs. Good. The ribs 14, 16, and 18 may be provided with sipes that cross the ribs. Here, sipe refers to a notch having a minute groove width (usually 1 mm or less), and is closed when the tire is brought into contact with a normal load. On the other hand, a lateral groove has a groove width larger than that of a sipe, and does not close when contacting with a normal load. Thus, the ribs 14, 16, and 18 may be provided with lateral grooves and sipes, and the tread pattern of the tire according to this embodiment is symmetrical with respect to the tire equatorial plane CL including these lateral grooves and sipes. It may be a tread pattern or a tread pattern that is asymmetric with respect to the tire equatorial plane CL by changing the arrangement of lateral grooves and sipes. Here, the normal load is a load that is 80% of the normal load, and the normal load is the “maximum load capacity” in the JATMA standard, and the “maximum load” described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard. Value "or" LOAD CAPACITY "in the ETRTO standard.

  Although some embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  In order to show the effect of the embodiment, pneumatic radial tires for passenger cars of Examples 1 to 4 and Comparative Example (size: 225 / 45R17) were prototyped. Each prototype tire was manufactured by changing the specifications shown in Table 1 with the same basic tread pattern and tire internal structure. Specifically, the comparative example is a control tire, which is an example in which the entire tread surface is formed in the reference contour line L without causing the grounding surfaces of the central rib 14 and the intermediate ribs 16 and 16 to bulge. Examples 1 to 3 are examples in which the ground planes of the central rib 14 and the intermediate ribs 16 and 16 are expanded relative to the comparative example. Example 4 is an example in which the groove widths of the center main groove 12A and the shoulder main groove 12B are changed as compared with the comparative example, and the grounding surfaces of the central rib 14 and the intermediate ribs 16 and 16 are bulged.

  About each pneumatic tire of Examples 1-4 and a comparative example, noise performance and steering stability were evaluated. The evaluation method is as follows.

(1) Noise performance When a test tire is assembled on a regular rim and filled with a regular internal pressure, the noise when the speed is 60 km / h is measured according to the JASO standard and the sound pressure at 1 kHz is measured, and the reciprocal number is indexed. evaluated. The result of Comparative Example 1 is set to 100, and the larger the index, the smaller the noise and the better the noise performance.

(2) Steering stability A test tire assembled with a regular rim and filled with a regular internal pressure was mounted on a test vehicle, and the vehicle was subjected to straight running and cornering running on a dry road surface. The evaluation is a seven-step evaluation with the result of the comparative example being “4”, and the larger the number, the better the steering stability.

  The results are as shown in Table 1. In Example 1, the contact surface was bulged with different bulge amounts in the central rib and the pair of intermediate ribs, so that the comparative example was not bulged. Noise due to air column resonance in the high frequency range was reduced. In the second embodiment, the bulge amount H of the central rib> the bulge amount H1 of the outer intermediate rib when the vehicle is mounted> the bulge amount H2 of the inner intermediate rib when the vehicle is mounted in the second embodiment. Thus, the steering stability was improved while maintaining the noise reduction effect with respect to Example 1. In the third embodiment, the ratio of these three bulge amounts is set to a value that is almost equally divided, whereby the frequency band of the air column resonance can be evenly distributed, and the noise reduction effect is achieved with respect to the second embodiment. Further improved. In Example 4, although the groove width wa of the center main groove is as small as ½ of the groove width wb of the shoulder main groove, the bulging amount H1 of the outer intermediate rib when the vehicle is mounted is set to the bulging amount of the central rib. Since it was set to 1/3 or less of H, the difference in tube resonance frequency between the center main groove and the shoulder main groove was increased, and the noise reduction effect could be enhanced.

DESCRIPTION OF SYMBOLS 10 ... Tread part, 12 ... Main groove, 12A ... Center main groove, 12B ... Shoulder main groove, 14 ... Center rib, 14A ... Ground surface of center rib, 16 ... Intermediate rib, 16A ... Ground surface of intermediate rib, 16- DESCRIPTION OF SYMBOLS 1 ... Outer intermediate rib at the time of vehicle mounting, 16-2 ... Inner intermediate rib at the time of vehicle mounting, 18 ... Shoulder rib, CL ... Tire equatorial plane, C ... Tire circumferential direction, H ... Swelling amount of central rib, H1 ... The amount of bulging of the outer intermediate rib when mounted on the vehicle, H2: The amount of bulging of the inner intermediate rib when mounted on the vehicle, Ko ... outer in the tire radial direction, L ... reference contour line, Wo ... outer in the tire width direction,

Claims (3)

There are provided a plurality of main grooves extending in the tire circumferential direction in which groove positions and groove widths are provided symmetrically with respect to the tire equatorial plane, and ribs formed between the main grooves and crossing the ribs. In a pneumatic tire having a plurality of ribs not provided in the tread portion,
All of the plurality of ribs formed between the main grooves, or other ribs except for one of the plurality of ribs, the ground contact surface is radially outward with respect to the reference contour line of the tread portion. A pneumatic tire characterized in that the amount of bulge with respect to the reference contour line of each rib is different from each other. A pair of center main grooves extending in the tire circumferential direction in which a groove position and a groove width are provided symmetrically with respect to the tire equatorial plane, and a groove position and a groove with respect to the tire equatorial plane outside the center main groove in the tire width direction. A pair of shoulder main grooves extending in the tire circumferential direction provided symmetrically in width, a central rib formed between the pair of center main grooves, and formed between the center main groove and the shoulder main grooves In a pneumatic tire provided with a pair of intermediate ribs and a pair of shoulder ribs formed on the outer side in the tire width direction of the pair of shoulder main grooves in the tread portion,
Of the pair of intermediate ribs, at least the outer intermediate rib and the central rib when mounted on the vehicle have a ground contact surface bulging outward in the tire radial direction with respect to the reference contour line of the tread portion, and from the reference contour line The bulging amount of the pneumatic tire is larger at the central rib than at the outer intermediate rib when mounted on the vehicle, and larger at the outer intermediate rib when mounted on the vehicle than the inner intermediate rib when mounted on the vehicle. .   The groove width of the center main groove is less than or equal to ½ of the groove width of the shoulder main groove, and the amount of bulging from the reference contour line at the outer intermediate rib when the vehicle is mounted is the height at the central rib. The pneumatic tire according to claim 2, wherein the amount is not more than 1/3 of the bulging amount from the reference contour line.

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