Pneumatic tire

Abstract

To provide a pneumatic tire which is easily assembled to a rim, while attaining improvement in bead durability.SOLUTION: A carcass of a pneumatic tire comprises wind-up parts 4b that are wound up respectively around a bead core 5 and extend outward in a tire radial direction. A bead base of a bead part 4 has a maximum taper angle θ1 at a tire lateral cross section including a tire rotation axis before being fitted to a rim R. At a tire lateral cross section when fitted to the rim R at an internal pressure of 10% of a normal internal pressure, a third straight line L3 that connects a point Q where a first straight line L1 passing a rim alienation point P and extending in a maximum thickness direction of the bead part 4 intersects with a wind-up part 6b, and a point R where a second straight line L2 extending in a tire axial direction from the bead core 5 intersects with the wind-up part 6b, is inclined at an angle θ2 relative to the tire axial direction. The maximum taper angle θ1 and the angle θ2 satisfy the formula (1). 50°≤θ2-θ1≤90°...(1)SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to pneumatic tires.

Background Art

[0002] Conventionally, pneumatic tires have been proposed to improve bead durability (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above Patent Document 1, due to the configuration including two folded reinforcing plies, the width of the bead base may become excessive, making the rim assembly work difficult.

[0005] The present disclosure has been devised in view of the above actual situation, and the main object is to provide a pneumatic tire that is easy to assemble onto a rim while improving bead durability.

Means for Solving the Problems

[0006] The present disclosure is a pneumatic tire to be mounted on a 15° tapered rim, a tread portion, a pair of sidewall portions, a pair of bead portions each having a bead core embedded therein, and a carcass extending between the pair of bead portions so as to straddle the bead cores, The carcass includes a carcass ply having a body portion extending between the pair of bead portions and a winding portion continuous with the body portion and wound around the bead core from the inner side to the outer side in the tire axial direction and extending outward in the tire radial direction. In a tire cross section including the tire rotation axis before mounting on the rim, the bead base of the bead portion has a maximum taper angle θ1 with respect to the tire axial direction, excluding the heel portion. In a tire cross section where the tire is mounted on the rim at an internal pressure of 10% of the normal internal pressure and in a no-load state, a third straight line L3 connecting a point Q where a first straight line L1 extending in the maximum thickness direction of the bead portion intersects the winding portion and passing through a rim separation point P where the outer surface of the bead portion in the tire axial direction is separated from the rim and a point R where a second straight line L2 extending outward in the tire axial direction from the center of the bead core intersects the winding portion is inclined at an angle θ2 with respect to the tire axial direction. The maximum taper angle θ1 and the angle θ2 satisfy the relationship of the following formula (1). 50° ≤ θ2 - θ1 ≤ 90° …(1)

Advantages of the Invention

[0007] In the pneumatic tire of the present disclosure, since the maximum taper angle θ1 and the angle θ2 satisfy the relationship of the formula (1), the winding portion stands up in the rim assembly state and is arranged at a position away from the rim flange. As a result, when a load is applied to the pneumatic tire, the winding portion of the carcass ply generates a large tension and bears a part of the stress generated in the bead portion, so that the bead durability is enhanced. And since a configuration such as a reinforcing ply for reinforcing the bead portion becomes unnecessary, the width of the bead base is suppressed. Thereby, the incorporation into the rim becomes easy.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a tire cross-section including the tire rotation axis of the pneumatic tire 1 of the present embodiment.

[0010] The pneumatic tire 1 is a tire mounted on a 15° tapered rim R. The pneumatic tire 1 includes a tread portion 2, a pair of sidewall portions 3, a pair of bead portions 4, and a carcass layer 6.

[0011] A bead core 5 is embedded in each bead portion 4. The bead core 5 is formed, for example, in a polygonal cross-sectional shape in which a bead wire (not shown) made of steel is wound in multiple rows and multiple stages.

[0012] The carcass layer 6 extends between the pair of bead portions 4 so as to straddle the pair of bead cores 5. The carcass layer 6 includes a carcass ply 6A.

[0013] The carcass ply 6A is formed, for example, by covering an array of carcass cords (not shown) with topping rubber. For the carcass cords, for example, organic fibers such as polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers, and steel are applied. That is, the carcass ply 6A includes polyester cords.

[0014] The carcass ply 6A has a main body portion 6a and a turn-up portion 6b. The main body portion 6a extends between the pair of bead portions 4. The turn-up portion 6b is continuous with the main body portion 6a and is wound around the bead core 5 from the inner side to the outer side in the tire axial direction and extends to the outer side in the tire radial direction.

[0015] This pneumatic tire 1 has a belt layer 7 in the tread portion 2. The belt layer 7 is disposed on the outer side in the tire radial direction of the carcass layer 6. The belt layer 7 includes at least one sheet, and in this embodiment, it is composed of two belt plies 7A and 7B on the inside and outside in the tire radial direction. The belt plies 7A and 7B are formed, for example, by covering an array of belt cords with topping rubber. The belt cords are arranged in the tire circumferential direction. That is, the belt cords are preferably arranged at an angle of, for example, 15 to 45° with respect to the tire equator C. The belt cords are preferably made of a highly elastic material such as a steel cord. The belt layer 7 may be omitted.

[0016] FIG. 2 shows the bead portion 4 of the pneumatic tire 1 before mounting on the rim R in the same cross section as FIG. 1.

[0017] The bead portion 4 has a bead base 41. The bead base 41 constitutes the inner peripheral surface of the bead portion 4 and contacts the bead seat of the rim R.

[0018] The bead base 41 has a taper angle corresponding to the taper angle of the rim R (usually larger than the taper angle of the rim R). The bead base 41 has a maximum taper angle θ1 with respect to the tire axial direction. The maximum taper angle θ1 is the maximum taper angle in a region excluding the heel portion on the rim flange side (i.e., the outer side in the tire axial direction). When the taper angle of the bead base 41 is constant, the maximum taper angle θ1 is that angle. When the taper angle of the bead base 41 changes in multiple steps or continuously, the maximum taper angle θ1 is the maximum taper angle in a region excluding the heel portion. In this embodiment, the maximum taper angle θ1 is 20 to 30°.

[0019] When assembling the rim, since the bead base 41 is corrected by the bead seat of the rim R, the taper angle of the bead base 41 is measured in the state before being mounted on the rim R, as shown in FIG. 2. Further, since the taper angle of the bead base 41 may be affected by the bead heel interval BW (see FIG. 1), it is measured while holding the bead heel interval BW at a constant value (for example, the width of the standard rim in this embodiment) using a predetermined jig or the like.

[0020] The "standard rim" is the rim defined for each tire in the standard system including the standard on which the tire is based. For example, in the case of JATMA, it is the "Standard Rim", in the case of TRA, it is the "Design Rim", and in the case of ETRTO, it is the "Measuring Rim". In this application, unless otherwise specified, the rim R indicates the standard rim.

[0021] FIG. 3 shows a cross section of the tire in a state where it is mounted on the rim R at an internal pressure of 10% of the standard internal pressure and is unloaded.

[0022] The "standard internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. In the case of JATMA, it is the "maximum air pressure", in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0023] "Mounted at an internal pressure of 10% of the standard internal pressure" means a state in which the pneumatic tire 1 mounted on the rim R is adjusted to an internal pressure of 10% of the standard internal pressure after being once filled with the standard internal pressure. Filling with the standard internal pressure is to improve the contact between the flange portion of the rim R and the bead portion 4.

[0024] In FIG. 3, the point where the outer surface of the bead portion in the tire axial direction is separated from the rim is defined as the rim separation point P. And a straight line passing through the rim separation point P and extending in the maximum thickness direction of the bead portion 4 is defined as the first straight line L1.

[0025] Further, let the point where the first straight line L1 intersects the winding portion 6b be point Q. When the tip of the winding portion 6b does not reach the first straight line L1, the point on the winding portion 6b closest to the first straight line L1 (i.e., the tip of the winding portion 6b) is taken as point Q. Point Q is determined in consideration of the thickness of the carcass ply 6A. More specifically, point Q is determined at the center in the thickness direction of the carcass ply 6A (the same applies to point R described later).

[0026] Further, a straight line extending radially outward from the center 5o of the bead core 5 in the tire axial direction is defined as the second straight line L2. Further, the point where the second straight line L2 intersects the winding portion 6b is taken as point R. And the straight line connecting point Q and point R is defined as the third straight line L3.

[0027] When the inclination angle of the third straight line L3 with respect to the tire axial direction is the angle θ2, the maximum taper angle θ1 and the angle θ2 satisfy the relationship of the following formula (1). 50° ≤ θ2 - θ1 ≤ 90° …(1)

[0028] In the pneumatic tire 1, since the maximum taper angle θ1 and the angle θ2 satisfy the relationship of formula (1), the winding portion 6b stands up in the rim-assembled state and is arranged at a position far from the flange portion of the rim R. Thereby, when a load is applied to the pneumatic tire 1, a large tension is generated in the winding portion 6b of the carcass ply 6A, and a part of the stress generated in the bead portion 4 is borne, so that the bead durability is enhanced. And since a configuration such as a reinforcing ply for reinforcing the bead portion 4 becomes unnecessary, the width of the bead base 41 is suppressed. Thereby, it becomes easy to incorporate the pneumatic tire 1 into the rim R.

[0029] In this embodiment, since θ2 - θ1 is 50° or more, it becomes possible to easily move the winding portion 6b away from the flange portion of the rim R, the tension generated by the winding portion 6b increases, and the bead durability is enhanced. And since θ2 - θ1 is 90° or less, it is possible to suppress a decrease in bead durability due to excessive tension generated by the winding portion 6b. Further, an excessive maximum taper angle θ1 is suppressed, and it becomes easy to incorporate the pneumatic tire 1 onto the rim R. Also, it becomes possible to easily remove the pneumatic tire 1 from the rim R while suppressing damage to the bead base 41.

[0030] From such a viewpoint, a more desirable relationship between the maximum taper angle θ1 and the angle θ2 satisfies the following formula (2). 60° ≤ θ2 - θ1 ≤ 80° …(2)

[0031] FIG. 4 shows a bead 4A which is a modified example of the bead portion 4 in FIG. 3. The bead 4A includes an inner bead apex rubber 81 and an outer bead apex rubber 82.

[0032] The inner bead apex rubber 81 extends radially outward in the tire direction from the bead core 5. In the cross section shown in FIG. 4, the inner bead apex rubber 81 is formed in a tapered shape with a narrow tip.

[0033] The outer bead apex rubber 82 is arranged on the outer side in the tire axial direction from the winding portion 6b. By providing the outer bead apex rubber 82 outside the winding portion 6b, it becomes possible to easily move the winding portion 6b away from the flange portion of the rim R, and the tension generated by the winding portion 6b increases.

[0034] When the maximum thickness of the bead portion 4 from the rim separation point P is T0 and the thickness of the outer bead apex rubber 82 on the first straight line L1 is T1, it is desirable that the maximum thickness T0 of the bead portion 4 and the thickness T1 of the outer bead apex rubber 82 satisfy the relationship of the following formula (3). 0.05 ≤ T1 / T0 ≤ 0.20 …(3)

[0035] When T1 / T0 is 0.05 or more, the tension generated in the hoisting portion 6b increases, and the bead durability is enhanced. When T1 / T0 is 0.20 or less, it is possible to suppress a situation where the tension generated in the hoisting portion 6b becomes excessive and the bead durability decreases. Further, it is possible to suppress a situation where the rigidity of the bead portion 4 is excessively increased by the outer bead apex rubber 82 in terms of the wall thickness, and the bead durability is further improved.

[0036] The complex elastic modulus E* of the outer bead apex rubber 82 at 70°C is preferably 10 to 40 MPa.

[0037] Here, the complex elastic modulus E* is measured by collecting a viscoelastic measurement sample having a length of 20 mm, a width of 4 mm, and a thickness of 1 mm from the outer bead apex rubber 82 such that the tire circumferential direction is the long side. The complex elastic modulus E* is a value measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the conditions of an initial strain of 10%, an amplitude of ±2%, a frequency of 10 Hz, a deformation mode of tension, and a measurement temperature of 70°C in accordance with the provisions of JIS-K6394. Note that the thickness direction of the sample is the tire axis direction.

[0038] When the complex elastic modulus E* of the outer bead apex rubber 82 is 10 MPa or more, the deformation of the bead portion 4 is suppressed, and the bead durability is further improved. When the complex elastic modulus E* of the outer bead apex rubber 82 is 40 MPa or less, it is possible to suppress a situation where the rigidity of the bead portion 4 is excessively increased, and the bead durability is further improved.

[0039] From the above viewpoints, a more desirable complex elastic modulus E* of the outer bead apex rubber 82 at 70°C is 20 to 30 MPa.

[0040] In the state of FIG. 2, the tire axial width BBW of the bead base 41 is preferably 20 mm or less. In this pneumatic tire 1, since the configuration such as a reinforcing ply for reinforcing the bead portion 4 becomes unnecessary by optimizing the relationship between the maximum taper angle θ1 and the angle θ2, the width BBW of the bead base 41 can be easily set to 20 mm or less. Thereby, it becomes easy to incorporate the pneumatic tire 1 onto the rim R. Further, it becomes possible to easily remove the pneumatic tire 1 from the rim R while suppressing damage to the bead base 41.

[0041] The outer end 6e in the tire radial direction of the winding portion 6b is located outside the tire radial direction than the outer end in the tire radial direction of the inner bead apex rubber 81. Thereby, the bead portion 4 is strengthened by the tension generated in the winding portion 6b in a wider area, and the bead durability is improved.

[0042] The outer end 6e in the tire radial direction of the winding portion 6b is located outside the tire radial direction than the outer end in the tire radial direction of the outer bead apex rubber 82. Thereby, the bead portion 4 is strengthened by the tension generated in the winding portion 6b in an even wider area, and the bead durability is improved.

[0043] It is desirable that the outer end 6e in the tire radial direction of the winding portion 6b is located outside the tire radial direction than the maximum width position 3o of the sidewall portion 3. Thereby, the bead portion 4 and the sidewall portion 3 are strengthened by the tension generated in the winding portion 6b, and the durability of the pneumatic tire 1 is improved.

[0044] The distance H1 from the bead base line BBL of the outer end 6e in the tire radial direction of the winding portion 6b is preferably 101 to 130% of the distance H0 from the bead base line BBL of the maximum width position 3o of the sidewall portion 3. When the distance H1 is 101% or more of the distance H0, the bead portion 4 and the sidewall portion 3 are strengthened, and the durability of the pneumatic tire 1 is improved. When the distance H1 is 130% or less of the distance H0, it deforms flexibly from the sidewall portion 3 to the buttress portion when a load is applied, and the durability of the pneumatic tire 1 is improved.

[0045] As described above in detail, the pneumatic tire 1 of the present disclosure can be implemented in various modes without being limited to the above specific embodiments.

Example

[0046] A pneumatic tire with a size of 205 / 80R17.5 having the basic structure of FIGS. 1 to 3 was prototyped based on the specifications in the table, and its durability performance was evaluated. The test method is as follows.

[0047] <Durability performance> The above pneumatic tire was mounted on a rim of 17.5×6.0 with an internal pressure of 600 kPa and run on a drum at a load of 19.16 kN and a speed of 80 km / h, and the running distance until failure was measured. The result is an index with Example 1 being 100, and the larger the numerical value, the better the durability performance.

[0048]

Table 1

[0049] As is clear from Table 1, it was confirmed that the pneumatic tire of the example had a significantly improved durability performance compared to the comparative example.

[0050] A pneumatic tire with a size of 205 / 80R17.5 having the basic structure of FIGS. 1 to 3 was prototyped based on the specifications in Table 2, and its durability performance, rim assembly performance, and rim removal performance were evaluated. The test method is as follows.

[0051] <Durability performance> Similar to the above, the running distance until the above pneumatic tire failed was measured. The result is an index with Example 6 being 100, and the larger the numerical value, the better the durability performance.

[0052] <Rim assembly performance> Using a tire changer, the ease of the operation of incorporating the pneumatic tire onto the rim was evaluated by the operator's sense. The result is a score with Example 6 being 100, indicating that the larger the numerical value, the easier the operation and the better the rim incorporation performance.

[0053] <Rim removal performance> Using the tire changer, the ease of the operation of removing the pneumatic tire from the rim was evaluated by the operator's sense. The result is a score with Example 6 being 100, indicating that the larger the numerical value, the easier the operation and the better the rim removal performance.

[0054]

Table 2

[0055] Pneumatic tires with a size of 205 / 80R17.5 having the basic structure of FIGS. 1 to 4 were trial-produced based on the specifications in Table 3, and their durability performance, rim incorporation performance, and rim removal performance were evaluated. The test methods are as follows.

[0056] <Durability performance> Similar to the above, the driving distance until the pneumatic tire fails was measured. The result is an index with Example 9 being 100, indicating that the larger the numerical value, the better the durability performance.

[0057] <Rim incorporation performance> Similar to the above, the ease of the operation of incorporating the pneumatic tire onto the rim was evaluated by the operator's sense. The result is a score with Example 9 being 100, indicating that the larger the numerical value, the easier the operation and the better the rim incorporation performance.

[0058] <Rim removal performance> Similar to the above, the ease of the operation of removing the pneumatic tire from the rim was evaluated by the operator's sense. The result is a score with Example 9 being 100, indicating that the larger the numerical value, the easier the operation and the better the rim removal performance.

[0059]

Table 3

[0060] A pneumatic tire with a size of 205 / 80R17.5 having the basic structure of FIGS. 1 to 4 was prototyped based on the specifications in Table 4, and its durability performance, rim assembly performance, and rim dismounting performance were evaluated. The test methods are as follows.

[0061] <Durability performance> Similar to the above, the running distance of the pneumatic tire until failure was measured. The result is an index with Example 13 set to 100, indicating that the larger the numerical value, the better the durability performance.

[0062] <Rim assembly performance> Similar to the above, the ease of the operation of assembling the pneumatic tire onto the rim was evaluated by the operator's sensory evaluation. The result is a score with Example 13 set to 100, indicating that the larger the numerical value, the easier the operation and the better the rim assembly performance.

[0063] <Rim dismounting performance> Similar to the above, the ease of the operation of removing the pneumatic tire from the rim was evaluated by the operator's sensory evaluation. The result is a score with Example 13 set to 100, indicating that the larger the numerical value, the easier the operation and the better the rim dismounting performance.

[0064]

Table 4

[0065] [Appendix] The present disclosure includes the following aspects.

[0066] [Disclosure 1] A pneumatic tire mounted on a 15° tapered rim, comprising a tread portion, a pair of sidewall portions, a pair of bead portions each embedded with a bead core including a carcass extending between the pair of bead portions so as to straddle the bead core; the carcass includes a carcass ply having a main body portion extending between the pair of bead portions and a winding portion that is continuous with the main body portion and is wound around the bead core from the inner side in the tire axial direction to the outer side and extends outward in the tire radial direction; in a tire cross section including the tire rotation axis before mounting on the rim, the bead base of the bead portion has a maximum taper angle θ1 with respect to the tire axial direction, excluding the heel portion; in a tire cross section in a state where the tire is mounted on the rim at an internal pressure of 10% of the normal internal pressure and is unloaded, a third straight line L3 connecting a point Q where a first straight line L1 extending in the maximum thickness direction of the bead portion passing through a rim separation point P where the outer surface in the tire axial direction of the bead portion is separated from the rim and intersects the winding portion, and a point R where a second straight line L2 extending outward in the tire axial direction from the center of the bead core intersects the winding portion is inclined at an angle θ2 with respect to the tire axial direction; the maximum taper angle θ1 and the angle θ2 satisfy the relationship of the following formula (1); Pneumatic tire. 50° ≤ θ2 - θ1 ≤ 90° …(1) [Disclosure 2] The pneumatic tire according to Disclosure 1, wherein the maximum taper angle θ1 and the angle θ2 satisfy the relationship of the following formula (2). 60° ≤ θ2 - θ1 ≤ 80° …(2) [Disclosure 3] The pneumatic tire according to Disclosure 1 or 2, further including an inner bead apex rubber extending outward in the tire radial direction from the bead core and an outer bead apex rubber disposed on the outer side in the tire axial direction of the winding portion. [Disclosure 4] The pneumatic tire according to Disclosure 3, wherein the maximum thickness T0 of the bead portion from the rim separation point P and the thickness T1 of the outer bead apex rubber on the first straight line L1 satisfy the relationship of the following formula (3). 0.05 ≤ T1 / T0 ≤ 0.2 …(3) [Disclosure 5] The complex elastic modulus E* of the outer bead apex rubber at 70 °C is 10 to 40 MPa, for the pneumatic tire according to Disclosure 3 or 4. [Disclosure 6] The complex elastic modulus E* of the outer bead apex rubber at 70 °C is 20 to 30 MPa, for the pneumatic tire according to Disclosure 5. [Disclosure 7] The tire axial width of the bead base is 20 mm or less, for the pneumatic tire according to any one of Disclosures 1 to 6. [Disclosure 8] The radially outer end of the turn-up portion is located radially outside the maximum width position of the sidewall portion, for the pneumatic tire according to any one of Disclosures 1 to 7. [Disclosure 9] The carcass ply includes a polyester cord, for the pneumatic tire according to any one of Disclosures 1 to 8. [Disclosure 10] The maximum taper angle θ1 is 20 to 30 °, for the pneumatic tire according to any one of Disclosures 1 to 9.

Explanation of symbols

[0067] 1 Pneumatic tire 2 Tread portion 3 Sidewall portion 3o Maximum width position 4 Bead portion 4A Bead 5 Bead core 5o Center 6A Carcass ply 6a Body portion 6b Turn-up portion 6e Radially outer end 41 Bead base 81 Inner bead apex rubber 82 Outer bead apex rubber E* Complex elastic modulus L1 First straight line L2 Second straight line L3 Third straight line P Rim separation point R Rim T0 Maximum thickness T1 Thickness θ1 Maximum taper angle θ2 Angle

Claims

1. A pneumatic tire mounted on a 15° tapered rim, comprising: a tread portion; a pair of sidewall portions; a pair of bead portions each having a bead core embedded therein; a carcass extending between the pair of bead portions so as to straddle the bead core; the carcass includes a carcass ply having a main body portion extending between the pair of bead portions and a winding portion that is continuous with the main body portion and is wound from the inner side to the outer side in the tire axial direction around the bead core and extends outward in the tire radial direction; in a tire cross section including the tire rotation axis before mounting on the rim, the bead base of the bead portion has a maximum taper angle θ1 with respect to the tire axial direction, excluding the heel portion; mounted on the rim at an internal pressure of 10% of the normal internal pressure, and in a tire cross section in a no-load state, a third straight line L3 connecting a rim separation point P through which the outer surface in the tire axial direction of the bead portion separates from the rim, a point Q where a first straight line L1 extending in the maximum thickness direction of the bead portion intersects the winding portion, and a point R where a second straight line L2 extending outward in the tire axial direction from the center of the bead core intersects the winding portion is inclined at an angle θ2 with respect to the tire axial direction; the width of the bead base in the tire axial direction is 20 mm or less; the maximum taper angle θ1 and the angle θ2 satisfy the relationship of the following formula (1); a pneumatic tire. 50° ≤ θ2 - θ1 ≤ 90°... (1)

2. The pneumatic tire according to claim 1, wherein the maximum taper angle θ1 and the angle θ2 satisfy the relationship of the following formula (2). 60° ≤ θ2 - θ1 ≤ 80°... (2)

3. The pneumatic tire according to claim 1 or 2, further comprising an inner bead apex rubber extending outward in the tire radial direction from the bead core and an outer bead apex rubber disposed outside the winding portion in the tire axial direction.

4. The pneumatic tire according to claim 3, wherein the maximum thickness T0 of the bead portion from the rim separation point P and the thickness T1 of the outer bead apex rubber on the first straight line L1 satisfy the relationship of the following formula (3). 0.05 ≤ T1 / T0 ≤ 0.2... (3)

5. The complex elastic modulus E* measured under the conditions of an initial strain of 10% for the outer bead apex rubber, an amplitude of ±2%, a frequency of 10 Hz, a deformation mode of tension, and a measurement temperature of 70°C is 10 to 40 MPa. The pneumatic tire according to claim 3 or 4.

6. The complex elastic modulus E* measured under the conditions of the initial strain of the outer bead apex rubber: 10%, amplitude: ±2%, frequency: 10 Hz, deformation mode: tension, and measurement temperature: 70°C is 20 to 30 MPa. The pneumatic tire according to claim 5.

7. The outer end in the tire radial direction of the winding portion is located outside the tire radial direction from the maximum width position of the sidewall portion. The pneumatic tire according to any one of claims 1 to 6.

8. The carcass ply includes a polyester cord. The pneumatic tire according to any one of claims 1 to 7.

9. The maximum taper angle θ1 is 20 to 30°. The pneumatic tire according to any one of claims 1 to 8.

10. The carcass is composed of one said carcass ply. The pneumatic tire according to any one of claims 1 to 9.

11. There is no reinforcing ply for reinforcing the bead portion outside the winding portion. The pneumatic tire according to any one of claims 1 to 10.

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