Pneumatic tire

A pneumatic tire includes a bead portions and a bead core at the bead portions, the tire being mounted to a 15°-tapered specified rim. The bead portions include a portion inward in a radial direction of an extension line of an inner circumferential surface of the bead core, the extension line extending in the lateral direction, that is positioned outward in the tire lateral direction of an imaginary line passing through a first intersection point between the extension line and a tire inner surface and extends inward in the tire radial direction from the extension line at an angle perpendicular to the extension line. An angle α formed by the imaginary line and a line segment passing through a second intersection point between a bead base and the tire inner surface and the first intersection point between the extension line and the tire inner surface is from 0° to 25°.

TECHNICAL FIELD

The present technology relates to a pneumatic tire.

BACKGROUND ART

In pneumatic tires in the related art, bead portions are provided on both sides in a tire lateral direction, each including a bead core. A rim wheel engages with the bead portions, allowing the pneumatic tire to be mounted to the rim wheel. Additionally, in a heavy duty pneumatic tire used for a truck or a bus, retreading is generally performed to regenerate a tread after the tread wears and reaches the end of a primary service life thereof.

The retreading of a pneumatic tire that has reached a primary service life thereof is performed by retreading the pneumatic tire with the pneumatic tire removed from the rim wheel and then mounting the pneumatic tire to the rim wheel once again, when the pneumatic tire ages and the rubber oxidizes and becomes embrittled, a bead toe serving as a leading edge portion of the bead portion may deform and become damaged when the pneumatic tire is removed from or mounted to the rim wheel. Thus, among the pneumatic tires in the related art, there exist pneumatic tires that suppress damage to the bead toe. For example, according to the pneumatic tire described in Japan Unexamined Patent Publication No. 2004-511383, a pneumatic tire is formed so that a portion of the bead toe of the bead portion is rounded and an included angle of a portion of the bead toe is in a range from 105° to 150°, thereby suppressing deformation of and damage to the bead toe when the pneumatic tire is removed from or mounted to the rim wheel.

However, when a portion of the bead toe is rounded to suppress deformation of the bead toe, the surface area of the portion of the bead portion that engages with the rim wheel decreases, possibly decreasing a hermeticity at the engaging portion. When the hermeticity at the engaging portion between the bead portion and the rim wheel decreases, air leakage readily occurs during reinflation after retreading, making inflation difficult. This makes it very difficult to suppress deformation of the bead toe while ensuring reinflatability after retreading.

SUMMARY

The present technology provides a pneumatic tire capable of suppressing deformation of a bead toe while ensuring reinflatability.

A pneumatic tire according to an embodiment of the present technology includes a pair of bead portions disposed on both sides of a tire equatorial plane in a tire lateral direction, and a bead core provided to each of the pair of bead portions, the pneumatic tire being mounted to a 15°-tapered specified rim. The bead portions include a portion inward in a tire radial direction of an extension line of an inner circumferential surface of the bead core, the extension line extending in the tire lateral direction, the portion is positioned outward in the tire lateral direction of an imaginary line that passes through an intersection point between the extension line and a tire inner surface and extends inward in the tire radial direction from the extension line at an angle perpendicular to the extension line. An angle formed by the imaginary line and a line segment passing through an intersection point between the tire inner surface and an engaging portion that serves as the inner circumferential surface of the bead portion and engages with the specified rim and the intersection point between the extension line and the tire inner surface is from 0° to 25°.

In the pneumatic tire, the bead portions are preferably provided so that an angle formed by the line segment and a straight line that passes through both end portions of the engaging portion in the tire lateral direction is from 85° to 100°.

In the pneumatic tire, the engaging portion preferably includes a rubber layer having a complex elastic modulus from 3 MPa to 7 MPa, and an elongation at break from 200% to 350%.

A pneumatic tire according to an embodiment of the present technology achieves the effect of allowing suppression of deformation of a bead toe while ensuring reinflatability.

DETAILED DESCRIPTION

Pneumatic tires according to embodiments of the present technology are described in detail below with reference to the drawings. However, the technology is not limited to these embodiments. Constituents of the following embodiments include elements that are essentially identical or that can be substituted or easily conceived by one skilled in the art.

Herein, “tire lateral direction” refers to the direction that is parallel with a rotation axis of a pneumatic tire. “Inward in the tire lateral direction” refers to the direction toward the tire equatorial plane in the tire lateral direction. “Outward in the tire lateral direction” refers to the direction opposite the direction toward the tire equatorial plane in the tire lateral direction. Furthermore, “tire radial direction” refers to the direction orthogonal to the tire rotation axis. “Inward in the tire radial direction” refers to the direction toward the tire rotation axis in the tire radial direction. “Outward in the tire radial direction” refers to the direction away from the tire rotation axis in the tire radial direction. “Tire circumferential direction” refers to the direction of rotation about the tire rotation axis.

FIG. 1is a meridian cross-sectional view illustrating a main portion of a pneumatic tire according to an embodiment. A pneumatic tire1illustrated inFIG. 1is provided with a tread portion2in an outermost portion in a tire radial direction, as viewed in a meridian cross-section. The surface of the tread portion2, i.e., the portion that comes into contact with the road surface when a vehicle (not illustrated) mounted with the pneumatic tire1travels, is formed as a tread surface3. A plurality of circumferential main grooves15extending in a tire circumferential direction, and a plurality of lug grooves (not illustrated) that intersect the circumferential main grooves15are formed on the tread surface3. A plurality of land portions10are defined by the plurality of circumferential main grooves15and lug grooves on the tread surface3. Note that the number of the circumferential main grooves15, the interval of the lug grooves in the tire circumferential direction, the length and angle of the lug grooves, the groove width and groove depth of each groove, and the like are preferably set as appropriate. That is, a so-called tread pattern formed on the tread surface3is preferably set as appropriate.

Both ends of the tread portion2in the tire lateral direction are formed as shoulder portions4, and sidewall portions5are provided from the shoulder portions4to predetermined positions inward in the tire radial direction. In other words, the sidewall portions5are disposed at two positions on either side of the pneumatic tire1in the tire lateral direction.

Furthermore, a bead portion20is located inward of each sidewall portion5in the tire radial direction. The bead portions20are disposed at two positions on either side of a tire equatorial plane CL in a similar manner to that of the sidewall portions5. That is, a pair of the bead portions20are provided on both sides of the tire equatorial plane CL in the tire lateral direction. The pair of bead portions20are each provided with a bead core21, and a bead filler30is provided outward of the bead core21in the tire radial direction. The bead core21is formed by winding a bead wire, which is a steel wire, into a ring shape. The bead filler30is a rubber material that is disposed in a space defined by an end portion of a carcass6, described below, in the tire lateral direction, folded back at the position of the bead core21, outward in the tire lateral direction.

The bead portions20are each configured to be capable of being mounted on a 15°-tapered specified rim. Here, “specified rim” refers to an “applicable rim” defined by the Japan Automobile Tyre Manufacturers Association (JATMA), a “Design Rim” defined by the Tire and Rim Association (TRA), or a “Measuring Rim” defined by the European Tyre and Rim Technical Organisation (ETRTO). That is, the pneumatic tire1according to the present embodiment can be mounted on a specified rim in which a portion that engages with the bead portion20is inclined at an inclination angle of 15° with respect to a rotation axis.

A belt layer7is provided inward of the tread portion2in the tire radial direction. The belt layer7is, for example, a multilayer structure including four layers of belts71,72,73,74, and is made by covering a plurality of belt cords made from steel or an organic fiber material, such as polyester, rayon, or nylon, with a coating rubber, and executing a rolling process. Furthermore, the belt cords of the belts71,72,73,74differ in the defined inclination angle of a fiber direction of the belt cords with respect to the tire circumferential direction, and the belts are layered so that the fiber directions of the belt cords intersect each other, i.e., a crossply structure.

The carcass6is continuously provided inward of the belt layer7in the tire radial direction and on the side of the sidewall portions5proximal to the tire equatorial plane CL. The carcass6includes radial ply cords. The carcass6has a single layer structure made of one carcass ply or a multilayer structure made of a plurality of carcass plies, and extends between the bead cores21on either side in the tire lateral direction in a toroidal shape, forming the framework of the tire. Specifically, the carcass6is disposed from one bead portion20of the pair of bead portions20to the other bead portion20positioned on either side in the tire lateral direction, and turns back outward in the tire lateral direction along the bead cores21at the bead portions20, wrapping around the bead cores21and the bead fillers30. That is, the carcass6turns back around the bead cores21at the bead portions20so as to extend from inward of the bead cores21in the tire lateral direction through inward of the bead cores21in the tire radial direction to outward of the bead cores21in the tire lateral direction. The carcass ply of the carcass6thus provided is made by a process of covering a plurality of carcass cords made from steel or an organic fiber material, such as aramid, nylon, polyester, or rayon with a coating rubber and then a rolling process.

Additionally, an innerliner8is formed along the carcass6on the inner side of the carcass layer6or on the interior side of the pneumatic tire1of the carcass layer6.

FIG. 2is a detailed view of area G ofFIG. 1. A carcass reinforcing layer35made from steel cord is disposed in the portion of the carcass6that turns back around the bead cores21. The carcass reinforcing layer35is disposed layered on the carcass6on the outer side of the carcass6at the turned back portion of the carcass6, turns back from the inner side to the outer side in the tire lateral direction around the bead cores21in the same way as the carcass6, and is continuously disposed in the tire circumferential direction. That is, the carcass reinforcing layer35is positioned inward of the carcass6in the tire lateral direction at the portion where the carcass6is positioned inward of the bead cores21in the tire lateral direction, is positioned inward of the carcass6in the tire radial direction at the portion where the carcass6is positioned inward of the bead cores21in the tire radial direction, and is positioned outward of the carcass6in the tire lateral direction at the portion where the carcass6is positioned outward of the bead cores21in the tire lateral direction.

Additionally, the bead core21formed by winding a bead wire into a ring shape is formed into a substantially hexagonal shape as viewed in a tire meridian cross section. Specifically, the bead core21is formed into a substantially hexagonal shape when viewed as a whole with an inner circumferential surface22and an outer circumferential surface23formed substantially parallel, inclining inward in the tire radial direction from outward to inward in the tire lateral direction, and corner portions that project in the tire lateral direction at positions on both ends in the tire lateral direction.

Note that, when the bead core21is viewed in a tire meridian cross section, the inner circumferential surface22of the bead core21in this case is the surface indicated by an imaginary straight line that, of a plurality of bead wires that are aligned in a row at a position inward of the bead core21in the tire radial direction and constitute a surface of the bead core21, comes into contact with the portion exposed on a surface side of the bead core21. Similarly, when the bead core21is viewed in a tire meridian cross section, the outer circumferential surface23of the bead core21is the surface indicated by an imaginary straight line that, among the plurality of bead wires that are arranged in a single row at a position outward of the bead core21in the tire radial direction and constitute the surface of the bead core21, comes into contact with the portion exposed on the surface side of the bead core21.

Further, a bead base25which is the surface of the bead portion20inward in the tire radial direction, that is, the bead base25being the inner circumferential surface of the bead portion20inclines inward in the tire radial direction from outward to inward in the tire lateral direction similar to the inner circumferential surface22and the outer circumferential surface23of the bead core21. In other words, the bead base25inclines in the direction in which a bead toe26, which is the leading edge portion of the bead base25inward in the tire lateral direction, is positioned inward in the tire radial direction of a bead heel27, which is the end portion of the bead base25outward in the tire lateral direction. This bead base25is provided as an engaging portion that engages with a specified rim when the pneumatic tire1according to the present embodiment is mounted to a specified rim.

Additionally, in the bead portion20, a tire inner surface40is formed curved in a direction projecting inward in the tire lateral direction. In other words, the tire inner surface40, which is the surface on the inflated side of the pneumatic tire1, curves in a direction projecting inward in the tire lateral direction at the portion of the bead portion20. The bead toe26, which is one end of the bead base25, serves as an intersection point Q between this tire inner surface40and the bead toe25.

FIG. 3is a detailed view of area H ofFIG. 2. The portion of the bead portion20inward in the tire radial direction of an extension line A of the inner circumferential surface22of the bead core21, the extension line A extending in the tire lateral direction, is positioned outward in the tire lateral direction of an imaginary line B that passes through an intersection point P between the extension line A and the tire inner surface40and extends inward in the tire radial direction from the extension line A at an angle perpendicular to the extension line A. Specifically, the extension line A is an imaginary line that extends inward in the tire lateral direction from the inner circumferential surface22of the bead core21at an inclination angle with respect to the rotation axis of the pneumatic tire1that is the same as an inclination angle of the inner circumferential surface22, and the intersection point P is an intersection point between this extension line A and the tire inner surface40. Further, the imaginary line B is an imaginary line that is perpendicular to the extension line A at the intersection point P and extends inward in the tire radial direction from the intersection point P. Furthermore, in the bead portion20, the entire portion inward of the extension line A in the tire radial direction is positioned outward of the imaginary line B in the tire lateral direction.

Note that the bead core21is formed by winding a bead wire into a ring shape, and the inner circumferential surface22of the bead core21is configured by arranging the bead wire in a single row. That is, when the bead core21is viewed in a tire meridian cross section, the inner circumferential surface22is not linear, but rather configured so that the circles, which are the cross-sectional shapes of the bead wires, are aligned in a row. As a result, the extension line A is set as an imaginary straight line that comes into contact with the portion of the bead wires constituting the inner circumferential surface22that is exposed on the front surface side of the bead core21. Further, the bead wires constituting the inner circumferential surface22of the bead core21may not be neatly aligned in a row. In such a case, the extension line A is set as an imaginary straight line that comes into contact with the portion of the bead wires equivalent to about half of those constituting the inner circumferential surface22that is exposed on the surface side of the bead core21.

Additionally, the bead core21is formed so that an angle β of the extension line A with respect to a straight line D perpendicular to the tire equatorial plane CL is within a range from 13° to 17°. That is, in the bead core21, the angle of the inner circumferential surface22with respect to the rotation axis of the pneumatic tire1is within a range from 13° to 17°, and the inner circumferential surface22is inclined with respect to the rotation axis in a direction in which a diameter of the inner circumferential surface22increases from inward to outward in the tire lateral direction.

Additionally, the bead portion20is formed so that an angle α formed by the imaginary line B and a line segment C that passes through the bead toe26and the intersection point P, that is, the line segment C passes through the intersection point Q and the intersection point P, is within a range from 0° to 25°. Here, the portion of the tire inner surface40near the bead toe26in a tire meridian cross-sectional view is formed into a linear shape, and thus the line segment C is generally a straight line along the tire inner surface40. Note that portion of the tire inner surface40near the bead toe26does not need to be formed into a linear shape. In this case, regardless of the shape of the tire inner surface40, the line segment C is a straight line that passes through the intersection point P between the extension line A and the tire inner surface40and the intersection point Q between the bead base25and the tire inner surface40. The bead portion20is configured so that the angle α formed by the imaginary line B and the line segment C as thus defined is within the range from 0° to 25°.

Additionally, the bead portion20is formed so that an angle γ formed by the line segment C and a straight line E that passes through both end portions of the bead base25in the tire lateral direction, that is, the line segment E that passes through the bead heel27and the bead toe26of the bead base25is within a range from 85° to 100°. Note that while, in the pneumatic tire1according to the present embodiment, the bead base25in a tire meridian cross-sectional view is formed into a linear shape and thus the straight line E and the bead base25substantially coincide, the bead base25may be formed into a shape other than a straight line. The bead base25may be, for example, formed to be curved in the middle. In this case, the straight line E may be a straight line that passes through the bead toe26, which is the leading edge portion inward of the bead base25in the tire lateral direction, and the bead heel27, which is the end portion of the bead base25outward in the tire lateral direction, regardless of the shape of the bead base25. The bead portion20is configured so that the angle γ formed by the line segment C and the straight line E as thus defined is within the range from 85° to 100°.

Note that the relative relationships and angles of these portions are defined after vulcanization molding in the mold, and prior to assembly of the pneumatic tire1to the specified rim, without a load applied. Specifically, a distance in the tire lateral direction between the bead heels27of each of the bead portions20positioned on both sides in the tire lateral direction is defined with the pneumatic tire1mounted to the specified rim in an unloaded state.FIG. 4is an explanatory diagram of a rim cushion rubber. A rim cushion rubber28is disposed radially inward and laterally outward of the bead core21and the turned back portion of the carcass6at the bead portion20. The rim cushion rubber28is the rubber layer constituting a contact surface of the bead portion20against the specified rim. The bead base25is made from the rim cushion rubber28. This rim cushion rubber28is a rubber layer having a complex elastic modulus from 3 MPa to 7 MPa, and an elongation at break from 200% to 350%. Note that the complex elastic modulus here refers to the value obtained by the measurement method defined in JIS (Japanese Industrial Standard) K7244-4: 1999 (measurement temperature: 60°, initial strain: 10%, amplitude: ±1%, frequency: 10 Hz, deformation mode: tension). Additionally, the elongation at break here is the elongation at break described in JIS K6251:2010.

When the pneumatic tire1thus configured is mounted to a vehicle, the pneumatic tire1is first mounted by engaging the bead base25with the specified rim, and then is inflated. The pneumatic tire1is thus mounted to the vehicle while mounted to the rim. The pneumatic tire1according to the present embodiment is used as a heavy duty pneumatic tire1mounted to a large vehicle such as a truck or a bus, for example.

When a vehicle with the pneumatic tire1mounted thereto is driven, the pneumatic tire1rotates while the portion of the tread surface3positioned at the bottom comes into contact with the road surface. The vehicle is driven by the transmission of a driving force and a braking force to the road surface as well as the generation of a swiveling force by a friction force between the tread surface3and the road surface. With the vehicle thus driven by the friction force between the tread surface3and the road surface, the tread portion2gradually wears in accordance with the distance traveled, reaching a wear threshold when the estimated distance traveled after mounting to the vehicle increases and making it no longer possible to drive the vehicle using the pneumatic tire1.

According to the heavy duty pneumatic tire1, when the tread portion2is worn, the tread portion2is regenerated by retreading. In other words, the tread portion2can be regenerated by refurbishing. This retreading is performed with the pneumatic tire1removed from the specified rim. Once this retreading is completed, the pneumatic tire1is mounted to the rim once again, reinflated, and mounted to the vehicle.

While retreading is thus performed when the tread portion2is worn, making it possible to regenerate the tread portion2, the rubber constituting the pneumatic tire1generally deteriorates over time or significant stress continually acts on the bead base25, which is the engaging portion, when the traveled distance of the vehicle increases, causing the bead toe26to rise from the rim and readily deform.

In response, in the pneumatic tire1according to the present embodiment, the portion of the bead portion20inward of the extension line A in the tire radial direction is positioned outward of the imaginary line B in the tire lateral direction, making it possible to avoid arrangement of rubber in the region where deformation of the bead toe26is significant and thus suppress deformation of the bead toe26. In other words, the portion of the bead portion20inward of the extension line A in the tire radial direction is positioned outward of the imaginary line B in the tire lateral direction, making it possible to form the bead toe26into a shape that suppresses inward projection in the tire lateral direction. While binding force by the bead core21on the bead toe26decreases as the amount of inward projection in the tire lateral direction increases, causing a tendency of a rise from the rim and deformation, the bead toe26is given a shape that suppresses inward projection in the tire lateral direction, making it possible to avoid arrangement of the rubber in the region where deformation of the bead toe26is significant. This arrangement allows for suppression of deformation of the bead toe26.

Additionally, the angle α formed by the imaginary line B and the line segment C is within the range from 0° to 25°, making it possible to not only suppress deformation of the bead toe26but also ensure reinflatability after the tread portion2reaches the service life thereof and is retreaded. That is, when the angle α formed by the imaginary line B and the line segment C is less than 0°, suppression of the amount of inward projection of the bead toe26in the tire lateral direction becomes difficult, making it difficult to suppress deformation of the bead toe26. On the other hand, when the angle α formed by the imaginary line B and the line segment C is greater than 25°, the length of the bead base25in a tire meridian cross-sectional view, that is, the width of the bead base25in the tire lateral direction decreases excessively, possibly causing an excessive decrease in the width of the engaging portion between the bead base25and the specified rim. In this case, adhesion of the bead base25and the specified rim becomes difficult, possibly causing continuous air leakage from gaps between the bead base25and the specified rim during reinflation after retreading and a decrease in reinflatability. In response, in the pneumatic tire1according to the present embodiment, the angle α formed by the imaginary line B and the line segment C is within the range from 0° to 25°, making it possible to suppress air leakage during reinflation while suppressing inward projection of the bead toe26in the tire lateral direction. This makes it possible to suppress deformation of the bead toe26while ensuring reinflatability.

Additionally, the bead portion20is formed so that the angle γ formed by the line segment C on the tire inner surface40side and the straight line E on the bead base25side is within the range from 85° to 100°, making it possible to more reliably suppress deformation of the bead toe26as well as provide reinflatability in a compatible manner. That is, when the angle γ formed by the line segment C and the straight line E is less than 85°, both relative angles of the connection portion of the tire inner surface40and the bead base25are relatively small and may cause the bead toe26to readily deform. In other words, when the angle γ formed by the line segment C and the straight line E is less than 85°, it may be difficult to increase the angle of the bead toe26in a tire meridian cross-sectional view to the extent that allows suppression of deformation. On the other hand, when the angle γ formed by the line segment C and the straight line E is greater than 100°, the width of the bead base25is difficult to maintain, possibly causing difficulties in ensuring reinflatability. In response, in the pneumatic tire1according to the present embodiment, the angle γ formed by the line segment C and the straight line E is within the range from 85° to 100°, making it possible to increase the angle of the bead toe26at a size that allows reinflatability to be ensured, and thus suppress deformation of the bead toe26. This makes it possible to more reliably suppress deformation of the bead toe26while ensuring reinflatability.

Additionally, the rim cushion rubber28is provided as a rubber layer having a complex elastic modulus from 3 MPa to 7 MPa, and an elongation at break from 200% to 350%, making it possible to suppress chipping of the bead toe26and ensure cut resistance. That is, when the complex elastic modulus of the rim cushion rubber28exceeds 7 MPa, the elongation at break decreases to lower than 200%, possibly causing a decrease in the elasticity of the rim cushion rubber28. In this case, the flexibility of the bead toe26also decreases, possible causing chipping in the bead toe26when a large load acts on the bead toe26during removal from the specified rim. On the other hand, when the complex elastic modulus of the rim cushion rubber28is less than 3 MPa, the strength of the rim cushion rubber28decreases, possibly causing cracks to readily be generated when a sharp object comes into contact with the rim cushion rubber28. In response, in the pneumatic tire1according to the present embodiment, the rim cushion rubber28has a complex elastic modulus from 3 MPa to 7 MPa, and an elongation at break from 200% to 350%, making it possible to provide both elasticity and strength in a compatible manner at or near the portion that engages with the specified rim. This makes it possible to suppress chipping of the bead toe26and ensure cut resistance.

EXAMPLES

FIGS. 5A, 5B and 5Care tables showing results of performance tests of pneumatic tires. In relation to the pneumatic tire1described above, performance evaluation tests conducted on pneumatic tires1of a Conventional Example and a Comparative Example, and pneumatic tires1according to embodiments of the present technology will be described below. The performance evaluation tests were conducted for bead toe deformation, testing the deformation state of the bead toe6; reinflatability, testing whether reinflation is possible; and bead toe chipping, testing whether chipping occurs in the bead toe26.

These performance evaluation tests were conducted by mounting the pneumatic tires1with a tire size of 11R22.5 to a rim wheel of a specified rim defined by JATMA and a rim size of 2.5×7.50, adjusting the air pressure to a maximum air pressure (700 kPa) defined by JATMA, mounting the tire onto a drive shaft of a 2-D4 (front 2-rear 4 drive) test vehicle, and test-running the tires with the maximum load defined by JATMA applied.

Each test item was evaluated as follows. Bead toe deformation was evaluated by running the tire 100000 km on a test vehicle, measuring the amount of deformation of the bead toe26, and expressing the measurement result using the Conventional Example as an index value of 100. A higher value indicates less deformation of the bead toe26and superior bead toe deformation performance. Additionally, reinflatability was evaluated by mounting the pneumatic tire1that was measured for deformation of the bead toe26after running 100000 km on the test vehicle, and checking whether inflation is possible using a normal method. Additionally, bead toe chipping was evaluated by visually checking whether chipping occurred in the bead toe26when the pneumatic tire1is mounted to or removed from the rim wheel after running 100000 km on the test vehicle.

The evaluation test was conducted on 13 pneumatic tires1, including the pneumatic tire1of the Conventional Example, the pneumatic tire1of the Comparison Example, and the pneumatic tires1of Examples 1 to 11, which are according to the embodiments of the present technology. These pneumatic tires1are each configured with the bead portion20formed differently. Among these, in the pneumatic tire1of the Conventional Example, the angle α formed by the imaginary line B and the line segment C is −10°. That is, in the pneumatic tire1of the Conventional Example, the bead toe26is positioned inward of the imaginary line B in the tire lateral direction. Additionally, in the pneumatic tire1of the Comparative Example, the angle α formed by the imaginary line B and the line segment C is 30°. That is, in the pneumatic tire1of the Conventional Example, the bead toe26is far away from the imaginary line B, outward in the tire lateral direction, and the width of the bead base25is small.

In contrast, in Examples 1 to 11, which are examples of the pneumatic tire1according to the embodiments of the present technology, the angles α formed by the imaginary line B and the line segment C are each within the range from 0° to 25° Furthermore, in the pneumatic tires1according to the Examples 1 to 11, the angles γ formed by the straight line E and the line segment C each differ, and the complex elastic moduli and elongations at break of the rim cushion rubber28each differ.

The evaluation tests conducted using these pneumatic tires1show that the pneumatic tires1of Examples 1 to 11, unlike that of the Comparative Example, were each inflatable even after the primary service life thereof was reached, making it possible to ensure reinflatability, as illustrated inFIGS. 5A, 5B, and 5C. Additionally, it was found that the pneumatic tires1of Examples 1 to 11 are capable of suppressing bead toe deformation in contrast to the pneumatic tire1of the Conventional Example. That is, the pneumatic tires1according to Examples 1 to 11 are capable of suppressing deformation of the bead toe26while ensuring reinflatability.