Tire

Abstract

Provided is a tire that exhibits excellent rim slip resistance and rim fitting performance while suppressing a decrease in rim mountability. A tire 10 comprises a pair of bead parts 12. The bead parts 12 each have a base surface 32, a back surface 34, and a heel surface 36 connecting the base surface 32 and the back surface 34. When the length of the heel surface 36 in the tire width direction W is defined as a heel width length v, the length of the heel surface in the tire radial direction R is defined as a heel height h, the angle formed by a virtual extension line L1 extending toward the outside of the base surface 32 in the tire width direction W and a virtual extension line L3 extending toward the outside of the back surface 34 in the tire radial direction is defined as a base angle α [rad], and in a tire meridional cross-sectional view, the radius of curvature of a first connection portion 38 connecting the back surface 34 and the heel surface 36 is defined as R1, and the radius of curvature of a second connection portion 40 connecting the base surface 32 and the heel surface 36 is defined as R2, 0.07≤(R2×v) / (R1×h)×1 / α ≤0.58 is satisfied.

Description

Tire

[0001] The present invention relates to a tire.

[0002] A tire is mounted on a wheel by fitting a bead portion provided with a bead core into a rim. The rim fit, which is the ease of incorporating the tire onto the rim, is affected by the configuration of the bead portion. For example, Patent Document 1 discloses a pneumatic tire mounted on an applicable rim and in a reference state of no load with an internal pressure of atmospheric pressure, where the back portion is disposed on an inner surface facing the inner side in the tire width direction at the rim flange portion, and a flat surface portion extending linearly along the tire radial direction in the reference state is formed at a connection portion between the back portion and the heel portion.

[0003] International Publication No. 2014 / 1,260,98

[0004] The rim fit and the rim shift resistance, which is the resistance to displacement between the tire and the rim after the tire is mounted on the rim, are conflicting characteristics. That is, when the rim shift resistance is improved, the rim fit tends to decrease.

[0005] Also, the tire is preferably mounted uniformly in the tire circumferential direction along the rim. A tire having excellent rim fitting properties like this may be able to reduce the air resistance generated around the tire during rolling.

[0006] An object of the present invention is to provide a tire that is excellent in rim shift resistance and rim fitting properties while suppressing a decrease in rim fit.

[0007] A tire according to one aspect of the present invention is a tire that is assembled to a regular rim and comprises a pair of bead portions, the bead portion having a base surface facing the bead seat of the regular rim, a back surface facing the flange of the regular rim, and a heel surface connecting the base surface and the back surface, wherein the length of the heel surface in the tire width direction is the heel width length v, the length in the tire diameter direction is the heel height h, the angle between a virtual extension line extending outward in the tire width direction of the base surface and a virtual extension line extending in the tire diameter direction of the back surface is the base angle α [rad], and in a meridional cross-sectional view of the tire, the radius of curvature of the first connecting portion connecting the back surface and the heel surface is R1, and the radius of curvature of the second connecting portion connecting the base surface and the heel surface is R2, then the following formula (1) is satisfied.

[0008] 0.07 ≤ (R² × v) / (R¹ × h) × 1 / α ≤ 0.58 ... (1)

[0009] According to the present invention, it is possible to obtain a tire that has excellent resistance to rim slippage and rim fitting while suppressing a decrease in rim assembly performance.

[0010] This is an enlarged end view of the bead portion of the tire according to this embodiment. This is an enlarged view of part II in Figure 1.

[0011] Embodiments of the present invention relate to the following aspects.

[0012] [Aspect 1] A tire having a pair of bead portions and being assembled to a regular rim, wherein the bead portion has a base surface facing the bead seat of the regular rim, a back surface facing the flange of the regular rim, and a heel surface connecting the base surface and the back surface, wherein the length of the heel surface in the tire width direction is the heel width length v, the length in the tire diameter direction is the heel height h, the angle between a virtual extension line extending outward in the tire width direction of the base surface and a virtual extension line extending in the tire diameter direction of the back surface is the base angle α [rad], and in a meridional cross-sectional view of the tire, the radius of curvature of the first connecting portion connecting the back surface and the heel surface is R1, and the radius of curvature of the second connecting portion connecting the base surface and the heel surface is R2, the tire satisfies the following formula (1). 0.07 ≤ (R2 × v) / (R1 × h) × 1 / α ≤ 0.58 ... (1) [Aspect 2] The tire according to Aspect 1, wherein the heel width length v and the heel height h satisfy the relationship v < h. [Aspect 3] The tire according to Aspect 1 or 2, wherein when the bead width BW is the distance in the tire width direction from the bead toe to the rear, the bead width BW is 14 mm or more and 18 mm or less, the heel height h is 7.5 mm or less, and the heel width length v and the bead width BW satisfy the following formula (2). v / BW ≤ 0.4 ... (2) [Aspect 4] The tire according to any one of Aspects 1 to 3, wherein the heel surface has a convex curved surface with a radius of curvature of 10 mm or more in a meridional cross-sectional view of the tire, and the radius of curvature R1 of the first connecting part and the radius of curvature R2 of the second connecting part satisfy the following formula (3). 1 < R1 / R2 ≤ 3 ... (3) [Aspect 5] The tire according to aspect 3, wherein the base surface has a first base surface connected to the inner edge of the heel surface in the tire width direction, and a second base surface connected to the inner edge of the first base surface on the inner side in the tire width direction via a third connecting portion, at least one of the first base surface and the second base surface is straight in a tire meridional cross-section view, and the distance u in the tire width direction from the third connecting portion to the back surface is 50% or more of the bead width BW.[Aspect 6] The tire according to aspect 5, wherein the first base surface and the second base surface are straight in a meridional cross-section of the tire, the angle β between the first base surface and the tire width direction is 5 degrees or more and 10 degrees or less, and the angle γ between the second base surface and the tire width direction is greater than angle β and 15 degrees or less. [Aspect 7] The tire according to aspect 4, wherein a vent mark is provided on the heel surface.

[0013] (Definitions) The radial direction of a tire refers to the direction perpendicular to the tire's axis of rotation. The inner side of the radial direction of a tire refers to the side toward the tire's axis of rotation in the radial direction, and the outer side of the radial direction of a tire refers to the side away from the tire's axis of rotation in the radial direction. The circumferential direction of a tire refers to the direction around the tire's axis of rotation. The width direction of a tire refers to the direction parallel to the tire's axis of rotation. The inner side of the width direction of a tire refers to the side toward the tire's equatorial plane (tire equator line) in the width direction, and the outer side of the width direction of a tire refers to the side away from the tire's equatorial plane in the width direction. The tire equatorial plane is a plane perpendicular to the tire's axis of rotation and passing through the center of the tire's width. "Along with" a certain standard includes being along a direction within a range of less than ±20°, less than ±10°, or less than ±5° from a certain standard. "Center" includes the midpoint where the distance from two points is equal, and a range of ±10% of the distance between the two points from the midpoint. A "regular rim" refers to the "applicable rim" specified in JATMA, the "Design Rim" specified in TRA, or the "Measuring Rim" specified in ETRTO. Regular internal pressure refers to the "maximum air pressure" specified in JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or the "INFLATION PRESSURES" specified in ETRTO. Regular load refers to the "maximum load capacity" specified in JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or the "LOAD CAPACITY" specified in ETRTO.

[0014] Figure 1 shows the bead portion 12 on one side in the tire width direction W relative to the tire equatorial plane, in a meridional cross-sectional view of the tire 10 according to this embodiment. Note that the figure shows the tire portion before it is mounted on the rim and in an unloaded state.

[0015] The tire 10 is mounted on a standard rim 14 shown in Figure 1. The radial and width directions of the standard rim 14 are the same as the tire's radial direction R and tire's width direction W. The standard rim 14 comprises a bead seat 16, a flange 18, and a hump 20. The bead seat 16 extends in the tire's width direction W. The flange 18 extends from the outside of the bead seat 16 in the tire's width direction W to the outside in the tire's radial direction R. The hump 20 is provided on the inside of the bead seat 16 in the tire's width direction W and protrudes outward in the tire's radial direction R. The hump 20 has a convex curved surface in a meridional cross-sectional view of the tire.

[0016] The bead seat 16 has a base-facing surface 22 on the outer surface in the tire radial direction R between the flange 18 and the hump 20. In a meridional cross-section view of the tire, the base-facing surface 22 is linearly inclined outward in the tire radial direction R toward the outer side in the tire width direction W.

[0017] The flange 18 has a side surface 24 on the inner side in the tire width direction W, and a circumferential surface 26 connected to the outer side of the side surface 24 in the tire radial direction R. The side surface 24 extends in a direction along the tire radial direction R in a view of the tire meridional section. The circumferential surface 26 is a convex curved surface in a view of the tire meridional section, and extends outward in the tire width direction W toward the outer side in the tire radial direction R.

[0018] The outer end of the base facing surface 22 in the tire width direction W and the inner end of the side surface 24 in the tire radial direction R are connected via a smooth corner surface 27.

[0019] The tire 10, although not shown in its entirety, has a meridional cross-sectional shape similar to that of a conventional pneumatic tire. That is, the tire 10 of this embodiment has a tread portion, although not shown. The tire 10 further comprises a sidewall portion (not shown) and a bead portion 12. The tire 10 has, for example, a carcass layer 30 that extends from the tread portion to the bead portions 12 on both sides in a meridional cross-sectional view of the tire and is wound around a pair of bead cores 28, and on the radial side R of the carcass layer 30, it has a belt layer and, optionally, a belt cover layer, although not shown.

[0020] The bead portion 12 is the innermost part of the tire 10 in the radial direction R that contacts the regular rim 14. The bead portion 12 shown in the figure is provided with a bead core 28, which is a ring-shaped reinforcing material made of bundled piano wire or the like. The area around the bead core 28 is made up of various rubber layers.

[0021] The bead portion 12 has a base surface 32, a back surface 34, and a heel surface 36 connecting the base surface 32 and the back surface 34. The base surface 32 faces the bead seat 16 of the regular rim 14. The base surface 32 is the inner edge on the inner side of the tire radial direction R of the tire 10 and extends in a direction along the tire width direction W. The back surface 34 faces the flange 18 of the regular rim 14. The back surface 34 is located on the outer side of the base surface 32 in the tire width direction W. The back surface 34 and the heel surface 36 are connected via a first connecting portion 38. The first connecting portion 38 is a convex curved surface that protrudes outward from the bead portion 12. The radius of curvature of the first connecting portion 38 is R1. The heel surface 36 and the base surface 32 are connected via a second connecting portion 40. The second connecting portion 40 is a convex curved surface that protrudes outward from the bead portion 12. The radius of curvature of the second connecting portion 40 is R2.

[0022] The base surface 32 is the surface of the bead portion 12 in the region from the bead toe 33, which is the innermost end in the tire width direction W, to the second connecting portion 40. The base surface 32 has a shape that is recessed outward in the tire radial direction R. The base surface 32 has a first base surface 42 connected to the heel surface 36 via the second connecting portion 40, and a second base surface 44 connected to the inner end of the first base surface 42 in the tire width direction W. The first base surface 42 and the second base surface 44 are connected via a third connecting portion 46. The first base surface 42 and the second base surface 44 are straight lines in a tire meridional cross-sectional view. The first base surface 42 and the second base surface 44 have different angles with respect to the tire width direction. The base surface 32 is bent in a direction that is recessed outward in the tire radial direction R, starting from the third connecting portion 46.

[0023] The rear surface 34 extends outward in the tire radial direction R. The inner end of the rear surface 34 in the tire radial direction R is connected to the heel surface 36. The outer end of the rear surface 34 in the tire radial direction R is connected to the concave curved surface 48. In a view of the tire meridional section, the concave curved surface 48 extends outward in the tire width direction W toward the outer end of the tire radial direction R.

[0024] The heel surface 36 is formed such that, in a meridional cross-sectional view of the tire, the inner diameter of the heel surface 36 gradually increases toward the outside in the tire width direction W. The heel surface 36 has a convex curved surface that protrudes outward from the bead portion 12. The heel surface 36 is composed of a circular arc centered at RH. In a meridional cross-sectional view of the tire, the length of the heel surface 36 in the tire width direction W is defined as the heel width length v, and the length of the tire radial direction R is defined as the heel height h.

[0025] The heel width length v is the length in the tire width direction W from the back surface 34 to the second connecting portion 40. More specifically, the heel width length v is the length in the tire width direction W from the back surface 34 to the first intersection point P1, which is the intersection point of the first virtual extension line L1 extending outward in the tire width direction W of the base surface 32 and the second virtual extension line L2, which is the extension of the arc constituting the heel surface 36. The first virtual extension line L1 is an extension line extending outward in the tire width direction W of the first base surface 42 connected to the heel surface 36.

[0026] The heel height h is the length of the tire radial R from the second intersection point P2, which is the intersection of the first virtual extension line L1 and the third virtual extension line L3 extending in the tire radial direction R on the back surface 34, to the first connecting portion 38. More specifically, the heel height h is the length of the tire radial R from the second intersection point P2 to the third intersection point P3, which is the intersection of the second virtual extension line L2 and the third virtual extension line L3.

[0027] The angle between the first base surface 42 and the back surface 34 is defined as the base angle α [rad]. The base angle α is the angle between the first virtual extension line L1 and the third virtual extension line L3. The base angle α is the angle between the first virtual extension line L1 and the third virtual extension line L3 on the inner side in the tire width direction relative to the third virtual extension line L3. The base angle α is defined as the dominant angle.

[0028] An example of the procedure for mounting the tire 10 onto the regular rim 14 will be described. First, the bead portion 12 is elastically deformed toward the inside in the tire width direction W, and the regular rim 14 is positioned with the distance between the pair of bead portions 12 in the tire width direction reduced. Next, the bead portion 12 is elastically returned to the outside in the tire width direction W while sliding on the bead seat 16. In this process, the bead portion 12 moves toward the outside in the tire width direction W while crossing over the hump 20. In this way, the bead portion 12 is positioned between the flange 18 and the hump 20. The base surface 32 is supported by the base opposing surface 22, the back surface 34 is supported by the side surface 24, and the concave curved surface 48 is supported by the circumferential surface 26.

[0029] In this embodiment, the radius of curvature R1, R2, heel width length v, heel height h, and base angle α [rad] of the tire 10 satisfy the following formula (1).

[0030] 0.07 ≤ (R² × v) / (R¹ × h) × 1 / α ≤ 0.58 ... (1)

[0031] In the above formula (1), (R2 × v) contributes to rim slip resistance. That is, the smaller the radius of curvature R2 and heel width length v of the second connecting portion 40, the greater the contact area between the bead portion 12 after rim assembly and the regular rim 14, thus improving rim slip resistance.

[0032] In the above formula (1), (R1 × h) contributes to rim assembly performance. That is, the larger the radius of curvature R1 and heel height h of the first connecting portion 38, the more the heel surface 36 contacts the rim and the easier it is to overcome the hump 20. Therefore, when assembling the rim, the bead portion 12 can easily overcome the hump 20, improving rim assembly performance.

[0033] The base angle α contributes to both rim assembly and rim slip resistance. Specifically, a larger base angle α increases the contact area between the base surface 32 and the regular rim 14, thus improving rim slip resistance. On the other hand, a smaller base angle α reduces the resistance when the bead portion 12 crosses the hump 20 during rim assembly, thus improving rim assembly.

[0034] In this embodiment, the tire 10 satisfies the above formula (1), making it easier for the bead portion 12 to overcome the hump 20 of the regular rim 14. This suppresses a decrease in rim mounting performance and improves the adhesion between the bead portion 12 and the regular rim 14, thereby improving rim slip resistance.

[0035] Furthermore, in this embodiment, the tire 10 has reduced rim mounting performance, thus suppressing deformation of the bead portion 12 during rim mounting. As a result, the tire 10 is mounted uniformly in the circumferential direction along the regular rim 14, resulting in excellent rim fitting. Therefore, the tire 10, with its excellent rim fitting and resistance to rim slippage, is less prone to rim slippage during rolling. This maintains the state of uniform mounting in the circumferential direction along the regular rim 14 even during rolling, thereby suppressing turbulence in the air around the tire and reducing air resistance.

[0036] It is preferable that the relationship v < h is satisfied between the heel width length v and the heel height h. The larger the heel height h, the less resistance there is when the bead portion 12 goes over the hump 20, thus improving rim mounting performance. The smaller the heel width length v, the larger the contact area with the regular rim 14, thus improving rim slip resistance. Therefore, by satisfying the relationship v < h, the tire 10 can improve rim slip resistance while suppressing a decrease in rim mounting performance.

[0037] It is preferable that the bead width BW is 14 mm or more and 18 mm or less, the heel height h is 7.5 mm or less, and the heel width length v and bead width BW satisfy the following formula (2).

[0038] v / BW≦0.4...(2)

[0039] By having a heel height h of 7.5 mm or less, the back surface 34 makes more reliable contact with the side surface 24 of the flange 18, thereby improving rim fitting performance while suppressing a decrease in rim assembly performance. By having the heel width length v and bead width BW satisfy the above formula (2), the base surface 32 makes more reliable contact with the regular rim 14, thereby improving rim slip resistance.

[0040] The radius of curvature of the convex curved surface constituting the heel surface 36 is preferably 10 mm or more, and the radius of curvature R1 of the first connecting portion 38 and the radius of curvature R2 of the second connecting portion 40 preferably satisfy the following formula (3).

[0041] 1<R1 / R2≦3...(3)

[0042] A larger radius of curvature R2 makes it easier for the bead portion 12 to overcome the hump 20 of the regular rim 14, while a smaller R1 ensures sufficient contact area between the bead portion 12 and the regular rim 14, thus maintaining a balance between rim assembly performance and rim slip resistance.

[0043] The base surface 32 has a linear first base surface 42 and a second base surface 44 in a meridional cross-sectional view of the tire, and is bent outward in the radial direction of the tire starting from the third connecting portion 46. Preferably, the distance u in the tire width direction W from the third connecting portion 46 to the back surface 34 is 50% or more of the bead width BW. By having the first base surface 42 and the second base surface 44, the contact pressure from the bead toe 33 to the regular rim 14 side is increased, and the resistance to rim slippage can be improved. Because the distance u is 50% or more of the bead width BW, the bead portion 12 is more likely to conform to the shape of the bead seat 16, so a decrease in rim assembly performance can be suppressed.

[0044] The angle β formed by the first base surface 42 and the tire width direction W is 5 degrees or more and 10 degrees or less, and the angle γ formed by the second base surface 44 and the tire width direction W is preferably larger than the angle β and 15 degrees or less. When the angle β and the angle γ are within the above ranges, the bead portion 12 can be arranged at a more appropriate position with respect to the regular rim 14. The angles β and γ are obtuse angles.

[0045] As shown in FIG. 2, it is preferable that the tire 10 has vent marks 50 provided on the heel surface 36. During vulcanization molding, by discharging the gas between the molding surface of the mold and the tire surface through the vent holes provided on the molding surface, the occurrence of chipping on the tire surface is suppressed. At the same time as discharging the gas, rubber flows into the vent holes, so vent marks are formed on the tire surface after vulcanization molding. In the case of the present embodiment, when vent holes are formed in the molding surface of the mold (not shown) corresponding to the heel surface 36, gas can be efficiently discharged by discharging the gas from the vent holes during the vulcanization process, and the occurrence of chipping on the surface of the bead portion 12 can be suppressed. As a result, the tire 10 according to the present embodiment can have vent marks 50 formed on the heel surface 36. The vent marks 50 are preferably provided in the central portion when the heel surface 36 is evenly divided into three parts in the tire meridian cross-sectional view.

[0046] (Modification) The present invention is not limited to the above embodiment, and can be appropriately changed within the scope of the gist of the present invention. For example, in the case of the above embodiment, the heel surface has been described as having a convex curved surface protruding outward, but the present invention is not limited to this. That is, the heel surface may be linear in the tire meridian cross-sectional view.

[0047] In the case of the above embodiment, the base surface has been described as having a shape recessed outward in the tire diameter direction, but the present invention is not limited to this. For example, the base surface may be linear in the tire meridian cross-sectional view, or may be one convex curved surface that protrudes inward in the tire diameter direction.

[0048] Also, in the case of the above-described embodiment, the base surface has a first base surface and a second base surface connected to the inner edge on the inner side in the tire width direction of the first base surface. The case where the first base surface and the second base surface are linear in the tire meridian cross-sectional view has been described, but the present invention is not limited to this. For example, in the tire meridian cross-sectional view, the first base surface may be linear and the second base surface may be a convex curved surface that bulges toward the inner side in the tire radial direction. Further, the first base surface may be a convex curved surface that bulges toward the inner side in the tire radial direction and the second base surface may be linear. Furthermore, the base surface may have three or more different surfaces. When the first base surface is a convex curved surface, the first virtual extension line L1 is a tangent to the first base surface passing through P1.

[0049] Also, in the case of the above-described embodiment, the case where the base surface bends in a direction of depression toward the outer side in the tire radial direction starting from the third connecting portion has been described, but the present invention is not limited to this and may bend in a direction of protrusion toward the inner side in the tire radial direction.

[0050] (Sample) A test tire having a tire size of 275 / 35R19 was manufactured. The conditions of the tires of Examples 1 to 9 and the tires of Comparative Examples 1 and 2 are as shown in Table 1 below.

[0051] (Rim mounting performance) The time required for an operator to mount the test tire onto a rim of size 19 x 9.5J and apply an internal pressure of 230 [kPa] was measured. The reciprocal of the measured time was expressed as an index with the conventional example described later set to 100. A larger index value indicates a shorter time required and superior rim mounting performance. (Rim slip resistance) Each test tire was mounted onto a rim of size 19 x 9.5J and an internal pressure of 230 [kPa] was applied. The manufactured tires were mounted on a typical test vehicle and driven around a test course for three laps to measure the amount of slip between the rim and the tire. The evaluation results were expressed as an index using the reciprocal of the measured value, with Comparative Example 1 set to 100. A larger index value indicates superior rim slip resistance. (Low air resistance performance) Each test tire was mounted onto a rim of size 19 x 9.5J and an internal pressure of 230 [kPa] was applied. The fabricated tires were mounted on a typical test vehicle, and the vehicle speed during coasting was measured in accordance with JIS D1012. The rolling resistance was calculated using a multi-point regression method. The evaluation results are shown as an index with the conventional example set to 100. A higher index indicates less air resistance and superior low-air-resistance performance.

[0052]

[0053] 10 Tire 12 Bead section 14 Regular rim 16 Bead seat 18 Flange 20 Hump 22 Base opposing surface 24 Side surface 26 Circumferential surface 27 Corner surface 28 Bead core 30 Carcass layer 32 Base surface 33 Bead toe 34 Back surface 36 Heel surface 38 First connecting section 40 Second connecting section 42 First base surface 44 Second base surface 46 Third connecting section 48 Concave curved surface 50 Vent mark L1 First virtual extension line L2 Second virtual extension line L3 Third virtual extension line P1 First intersection P2 Second intersection P3 Third intersection R Tire radial direction W Tire width direction

Claims

1. A tire having a pair of bead portions and being mounted on a regular rim, wherein the bead portion has a base surface facing the bead seat of the regular rim, a back surface facing the flange of the regular rim, and a heel surface connecting the base surface and the back surface, and the length of the heel surface in the tire width direction is the heel width length v, the length in the tire diameter direction is the heel height h, the angle between a virtual extension line extending outward in the tire width direction of the base surface and a virtual extension line extending in the tire diameter direction of the back surface is the base angle α [rad], and in a meridional cross-sectional view of the tire, the radius of curvature of the first connecting portion connecting the back surface and the heel surface is R1, and the radius of curvature of the second connecting portion connecting the base surface and the heel surface is R2, such that the tire satisfies the following equation (1): 0.07 ≤ (R2 × v) / (R1 × h) × 1 / α ≤ 0.58 ... (1) 2. The tire according to claim 1, wherein the heel width length v and the heel height h satisfy the relationship v < h.

3. The tire according to claim 1 or 2, wherein the bead width BW is the distance in the tire width direction from the bead toe to the rear, the bead width BW is 14 mm or more and 18 mm or less, the heel height h is 7.5 mm or less, and the heel width v and the bead width BW satisfy the following formula (2): v / BW ≤ 0.4 ... (2) 4. The tire according to claim 1 or 2, wherein the heel surface has a convex curved surface with a radius of curvature of 10 mm or more in a meridional cross-sectional view of the tire, and the radius of curvature R1 of the first connecting portion and the radius of curvature R2 of the second connecting portion satisfy the following formula (3): 1 < R1 / R2 ≤ 3 ... (3) 5. The tire according to claim 3, wherein the base surface has a first base surface connected to the inner edge of the heel surface in the tire width direction, and a second base surface connected to the inner edge of the first base surface on the inner side in the tire width direction via a third connecting portion, at least one of the first base surface and the second base surface is straight in a tire meridional cross-sectional view, and the distance u in the tire width direction from the third connecting portion to the back surface is 50% or more of the bead width BW.

6. The tire according to claim 5, wherein the first base surface and the second base surface are linear in a meridional cross-sectional view of the tire, the angle β between the first base surface and the tire width direction is 5 degrees or more and 10 degrees or less, and the angle γ between the second base surface and the tire width direction is greater than angle β and 15 degrees or less.

7. The tire according to claim 4, wherein a vent mark is provided on the heel surface.

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