Pneumatic tire

Abstract

To provide a pneumatic tire capable of improving riding comfort performance while suppressing deterioration of low rolling performance.SOLUTION: The pneumatic tire 1 includes a cap rubber 2C having a rubber hardness B. In a tire meridian cross section of a normal state, a rim protector 10 having a top part 11 projecting to a tire outer side is formed on an outer surface side 4s of a first bead part side 4A. The rim protector 10 includes an inside circular arc surface 12 of a curvature radius C (mm) extending from a top part 11 to the inside in the tire radial direction and having a 12c central part in the tire outside. When a separation distance in the tire axial direction between the top portion 11 and a tire radial direction line RL defining a rim width of a normal rim R is H, the following formula (1) is satisfied. 12.8 ≤ H * B / C ≤ 93.5 (1) SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] Patent Document 1 listed below describes a pneumatic tire having a protrusion on the bead portion that protrudes axially outward. The protrusion is positioned so that at least a portion of the protrusion comes into contact with the arcuate surface at the outer end of the rim flange of a regular rim when the tire is mounted on a regular rim, inflated to a regular internal pressure, and under a regular load. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-186672 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for improved ride comfort. Ride comfort is evaluated as good when the vibration caused when riding over a protrusion on the road surface, such as a single protrusion, is reduced. One known method for improving ride comfort is to reduce the rigidity of the tread portion. However, simply reducing the rigidity of the tread portion tends to increase frictional resistance during driving, which can lead to poor rolling resistance.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire that can improve ride comfort while suppressing a decrease in low rolling resistance performance. [Means for solving the problem]

[0006] The present invention provides a pneumatic tire comprising a tread portion, first bead portions with bead cores embedded therein, and a cap rubber that forms the contact surface of the tread portion and has a rubber hardness of B (degrees), wherein, in a tire meridian cross section in a normal state where the pneumatic tire is mounted on a regular rim and is adjusted to a regular internal pressure and is unloaded, the outer surface of the first bead portion is formed with a rim protector that has an apex that protrudes outward from the tire and extends in the tire circumferential direction, the rim protector includes an inner arc surface with a curvature radius C (mm) that extends radially inward from the apex and has a center outside the tire, and where, when H is the axial distance between the apex and a radial line defining the rim width of the regular rim, the pneumatic tire satisfies the following formula (1): 12.8≦H×B / C≦93.5 (1) [Effects of the Invention]

[0007] By adopting the above-described configuration, the pneumatic tire of the present invention can improve ride comfort while suppressing deterioration in low rolling resistance performance. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a tire meridian cross-sectional view of a pneumatic tire showing one embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of a first sidewall portion and a first bead portion of FIG. [Figure 3] FIG. 1A is a perspective cross-sectional view of a pneumatic tire of the present embodiment, and FIG. 1B is a perspective cross-sectional view of a pneumatic tire of another embodiment. [Figure 4] FIG. 10 is a tire meridian cross-sectional view of a first sidewall portion and a first bead portion of another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The drawings include exaggerated representations and representations that differ from the dimensional ratios of the actual structure to facilitate understanding of the present invention. Furthermore, when there are multiple embodiments, the same or common elements are designated by the same reference numerals throughout the specification, and redundant explanations will be omitted.

[0010] FIG. 1 is a cross-sectional view of a pneumatic tire 1 (hereinafter sometimes simply referred to as "tire 1") according to one embodiment of the present invention, taken along the tire meridian including the tire rotation axis (not shown). The tire 1 of this embodiment is suitable for use as a tire for passenger cars, for example. However, the present invention may also be applied to tires for heavy loads, for example. FIG. 1 shows the tire 1 in its normal state.

[0011] In the case of a pneumatic tire for which various standards are established, the "normal state" refers to a state in which the tire is mounted on a normal rim R (hereinafter sometimes referred to as "rim R"), adjusted to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal state refers to a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal state. Furthermore, for components that cannot be measured in the normal state (for example, the internal materials of the tire 1), the values ​​are measured by placing the tire 1 in a state as close to the normal state as possible.

[0012] "Regular rim R" is the rim defined for each tire by the standard system that includes the standard on which the tire is based; for example, it is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. The rim R has a rim flange Rf. In this specification, the rim flange Rf is the part of the rim R that is located radially outward from the bead baseline BL. The bead baseline BL is an imaginary straight line extending parallel to the tire axial direction that defines the rim diameter Rr (see JATMA, etc.) of the rim R.

[0013] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0014] The tire 1 includes a tread portion 2 and a first bead portion 4A in which a bead core 5 is embedded. The tire 1 also includes a cap rubber 2C that forms a contact surface 2s of the tread portion 2 and has a rubber hardness of B (degrees). The tire 1 also includes a first sidewall portion 3A that is continuous with the tread portion 2 and the first bead portion 4A.

[0015] In addition, in the tire meridian cross section in the normal state, a rim protector 10 is formed on the outer surface 4s of the first bead portion 4A, which has an apex 11 (shown in Figure 2) that protrudes outward from the tire and extends in the tire circumferential direction.

[0016] FIG. 2 is an enlarged view of the first sidewall portion 3A and first bead portion 4A of the tire 1 in FIG. 1. For convenience, the rim R has been omitted from FIG. 2. As shown in FIG. 2, the rim protector 10 includes an inner arcuate surface 12. The inner arcuate surface 12 is an arc that extends radially inward from a peak 11 and has a center 12c outside the tire. The inner arcuate surface 12 is formed with a radius of curvature C (mm). This rim protector 10 comes into contact with the rim flange Rf (shown in FIG. 1) of the standard rim R during running. This suppresses deformation of the first bead portion 4A originating from the rim flange Rf. This reduces heat generation (energy loss) associated with rubber deformation in the first bead portion 4A during running, ultimately reducing rolling resistance. When the inner arcuate surface 12 is formed from a plurality of arcs, the radius of curvature C is determined by the average of the maximum and minimum values ​​of the radii of curvature of the arcs. The apex 11 is the outer end of the inner arcuate surface 12 in the tire axial direction.

[0017] The separation distance H of the rim protector 10 is an index for ensuring the contact area F (not shown) between the rim flange Rf and the rim protector 10, and this value has a significant impact on the contact area F. Similarly, the curvature radius C of the inner arcuate surface 12 is an index for ensuring the contact area F, and this value has a significant impact on the contact area F. Therefore, it can be said that the ratio (H / C) of the separation distance H to the curvature radius C can be used to evaluate low rolling resistance. Furthermore, the rubber hardness B of the cap rubber 2C is an index for damping vibrations during driving, and this value has a significant impact on the vibration damping effect. The cap rubber 2C is the part that first comes into contact with, for example, a protrusion (single protrusion) on the road surface, and vibrations caused by this single protrusion are transmitted to the vehicle via the cap rubber 2C, the first sidewall portion 3A, the first bead portion 4A, and the rim R. For this reason, it can be said that the rigidity of the cap rubber 2C has a significant impact on the vibration damping effect. From the above, it can be said that the ratio (H / C) applied with rubber hardness B (H×B / C) can evaluate low rolling resistance and ride comfort. The inventors then found the upper and lower limits of (H×B / C) from various experimental results, and in the present invention, they set it at 12.8≦A×B / C≦93.5. This makes it possible to improve ride comfort while suppressing deterioration of low rolling resistance. The separation distance H is the axial length of the tire between the apex 11 and the tire radial line RL, which defines the rim width Rw (see JATMA) of the rim R. The tire radial line RL is an imaginary straight line extending parallel to the tire radial direction.

[0018] In order to further suppress the deterioration of low rolling resistance, it is desirable to satisfy formula (2). 25.0≦H×B / C≦93.5 …(2) In particular, it is desirable to satisfy formula (3) in order to improve ride comfort. 25.0≦H×B / C≦61.0 …(3) By setting the lower limit to 25.0, the deterioration of low rolling resistance can be further suppressed, and by setting the upper limit to 61.0, the ride comfort can be further improved.

[0019] The separation distance H is preferably 4.0 to 12.0 mm. Because the separation distance H is 4.0 mm or more, in the normal state, the contact area F between the rim flange Rf and the rim protector 10 is ensured, suppressing deformation of the first bead portion 4A. To increase the contact area F, the separation distance H is more preferably 6.0 mm or more, more preferably 8.0 mm or more, and even more preferably 9.0 mm or more. Because the separation distance H is 12.0 mm or less, excessive increases in the mass of the rim protector 10 are suppressed, reducing heat generation. To keep the mass of the rim protector 10 small, the separation distance H is more preferably 11.5 mm or less, more preferably 11.0 mm or less, and even more preferably 10.5 mm or less. As an example, the separation distance H is preferably 6.0 to 11.5 (mm), more preferably 8.0 to 11.0.0 (mm), and even more preferably 9.0 to 10.5 (mm).

[0020] The rubber hardness B is preferably 48 to 74 degrees. Since the rubber hardness B is 74 degrees or less, the cap rubber 2C (shown in FIG. 1) can effectively damp vibrations during driving, particularly vibrations that occur when riding over a single protrusion. To improve ride comfort, the rubber hardness B is more preferably 72 degrees or less, more preferably 70 degrees or less, and even more preferably 68 degrees or less. Since the rubber hardness B is 48 degrees or more, excessive deformation of the tread portion 2 is suppressed, and basic low rolling resistance performance can be maintained. To maintain high low rolling resistance performance, the rubber hardness B is more preferably 50 degrees or more, more preferably 52 degrees or more, and even more preferably 54 degrees or more. For example, the rubber hardness B is preferably 50 to 72 degrees, more preferably 52 to 70 degrees, or even more preferably 54 to 68 degrees.

[0021] "Rubber hardness" refers to the Shore hardness (Hs) measured in accordance with JIS K 6253-3:2012 using a durometer type A at a temperature of 23°C. A sample for measuring Shore hardness is prepared by cutting out a piece from the tread portion 2 so that the tire radial direction is the thickness direction. The measurement is performed by pressing a measuring tool against the sample from the contact surface side of the hardness measurement sample.

[0022] The radius of curvature C is preferably 9.5 to 15.0 mm. Because the radius of curvature C is 15.0 mm or less, the contact area F between the rim flange Rf and the rim protector 10 is ensured in the normal state, suppressing deformation of the first bead portion 4A. To increase the contact area F, the radius of curvature C is more preferably 13.5 mm or less, even more preferably 12.0 mm or less, and even more preferably 10.5 mm or less. In a preferred embodiment, the radius of curvature C is 9.5 mm.

[0023] 1, the tire 1 includes a second sidewall portion 3B and a second bead portion 4B that is continuous with the second sidewall portion 3B radially inward and has a bead core 5 embedded therein. The second sidewall portion 3B and the second bead portion 4B in this embodiment have the same shapes as the first sidewall portion 3A and the first bead portion 4A, respectively, and therefore their description will be omitted. The second sidewall portion 3B and the second bead portion 4B may, for example, have shapes different from those of the first sidewall portion 3A and the first bead portion 4A.

[0024] The tire 1 of this embodiment includes a toroidal carcass 6. The tire 1 also includes, in the tread portion 2, a belt layer 7 disposed radially outward of the carcass 6, and a base rubber 2B disposed between the belt layer 7 and a cap rubber 2C. The tire 1 further includes a sidewall rubber 3G forming a first sidewall portion 3A, and a clinch rubber 4G forming a first bead portion 4A.

[0025] The carcass 6 is formed, for example, by one carcass ply 6A. The carcass ply 6A includes, for example, a main body portion 6a and a pair of turned-up portions 6b. The main body portion 6a extends, for example, between the first bead portion 4A and the second bead portion 4B. Each turned-up portion 6b is connected to the main body portion 6a and is turned up around the bead core 5 from the axially inner side to the axially outer side. In this embodiment, each turned-up portion 6b extends radially outward of the tire maximum width position M. Note that the carcass 6 may be formed, for example, by a plurality of carcass plies. The tire maximum width position M is determined by the axially outer end of the carcass ply 6A.

[0026] The carcass ply 6A includes a plurality of carcass cords and a topping rubber covering the cords (not shown). The carcass cords are made of organic fiber cords such as aramid or rayon. The carcass cords are preferably arranged at an angle of 70 to 90 degrees relative to the tire circumferential direction.

[0027] As shown in Fig. 1, the belt layer 7 is adjacent to the carcass 6 on the radially outer side in the tire radial direction in the tread portion 2. The belt layer 7 includes an outer belt ply 7A and an inner belt ply 7B located on the radially inner side of the outer belt ply 7A. The belt layer 7 may be configured, for example, with three or more belt plies. Each of the outer belt ply 7A and the inner belt ply 7B extends, for example, axially outward of the ground contact edges Te on both sides.

[0028] In this specification, the contact edge Te is the axially outer contact position that comes into contact with a flat surface when the tire 1 in a normal state is placed on the flat surface with 80% of the normal load and a camber angle of 0°. The axial distance between the contact edges Te is the contact width TW. The axial center of the contact width TW is the tire equator Co. The contact patch 2s includes the tire equator Co and extends at least to the contact edges Te on both sides.

[0029] For pneumatic tires for which various standards are established, "normal load" refers to the load specified for each tire in the standard system including the standard on which the tire is based. For JATMA, this is "maximum load capacity," for TRA, this is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, this is "LOAD CAPACITY." For tires for which various standards are not established, "normal load" refers to the maximum load that can be applied when using the tire in accordance with the above standards.

[0030] Each of the outer belt ply 7A and the inner belt ply 7B includes a plurality of belt cords arranged at an angle of 15 to 45 degrees with respect to the tire circumferential direction and a topping rubber covering the cords (not shown). The belt cords may be, for example, steel cords or organic fiber cords such as aramid or rayon.

[0031] Although not particularly limited, the rubber thickness d1 of the cap rubber 2C is set to be larger than the rubber thickness d2 of the base rubber 2B. This significantly improves ride comfort. If the rubber thickness d1 of the cap rubber 2C is excessively large, there is a risk that the rolling resistance may deteriorate. For this reason, the rubber thickness d1 of the cap rubber 2C is preferably 150% or more of the rubber thickness d2 of the base rubber 2B, more preferably 200% or more, and more preferably 900% or less, and even more preferably 400% or less. In this specification, the rubber thickness d1 of the cap rubber 2C corresponds to the value obtained by dividing the cross-sectional area of ​​the cap rubber 2C between the contact edges Te by the contact width TW in a tire meridian cross section. The rubber thickness d2 of the base rubber 2B is also defined in the same way as the rubber thickness d1 of the cap rubber 2C. Note that the base rubber 2B may not be provided on the radially outer side of the belt layer 7, and only the cap rubber 2C may be provided (not shown).

[0032] For example, the radially inner end 3i of the sidewall rubber 3G is located radially outward of the radially outer end Re of the rim flange Rf. For example, the radially outer end 4e of the clinch rubber 4G is located radially outward of the radially outer end Re of the rim flange Rf.

[0033] The rubber hardness G of the clinch rubber 4G is greater than the rubber hardness I of the sidewall rubber 3G. Such clinch rubber 4G can effectively suppress deformation of the first bead portion 4A during driving. The sidewall rubber 3G also helps improve ride comfort. Furthermore, the rubber hardness G of the clinch rubber 4G is greater than the rubber hardness B of the cap rubber 2C. Although not particularly limited, the rubber hardness G of the clinch rubber 4G is preferably 60 degrees or more, more preferably 65 degrees or more, and is preferably 75 degrees or less, and even more preferably 70 degrees or less.

[0034] As shown in FIG. 2, the rim protector 10 includes, for example, an outer surface 13 extending radially outward from the apex 11. In this embodiment, the outer surface 13 is formed as an arc having a center 13c outside the tire. The radius of curvature L of the outer surface 13 is preferably equal to or greater than the radius of curvature C of the inner arcuate surface 12, and more preferably greater than the radius of curvature C of the inner arcuate surface 12. Such an outer surface 13 can further suppress deformation of the first bead portion 4A during running. To effectively exert this effect, the difference (LC) between the radius of curvature L of the outer surface 13 and the radius of curvature C of the inner arcuate surface 12 is preferably equal to or greater than 5 mm, and more preferably equal to or greater than 10 mm.

[0035] In a normal tire 1, the radial distance D from the bead base line BL to the radially inner end 12i of the inner arcuate surface 12 is preferably 11.5 to 14.5 mm. Since the distance D is 11.5 mm or more and 14.5 mm or less, a large contact area F can be ensured. To ensure a large contact area F, the distance D is more preferably 12.0 mm or more, even more preferably 12.5 mm or more, more preferably 14.0 mm or less, and even more preferably 13.5 mm or less. In this specification, the inner end 12i of the inner arcuate surface 12 is defined as the position where the angle α of the tangent t to the outer surface 4s of the first bead portion 4A relative to a line in the radial direction of the tire is 10 degrees. The angle α is defined as being positive (plus) when the tangent t is inclined radially inward toward the axially inner side of the tire.

[0036] The rim protector 10 of this embodiment is formed from clinch rubber 4G. Such a rim protector 10 effectively suppresses deformation of the first bead portion 4A, further suppressing deterioration of low rolling resistance. However, the rim protector 10 is not limited to this form and may, for example, be formed from sidewall rubber 3G, or may be formed to include sidewall rubber 3G and clinch rubber 4G.

[0037] In a normal pneumatic tire 1, it is desirable that 50% or more of the length of the inner arcuate surface 12 of the rim protector 10 contacts the rim flange Rf (shown in FIG. 1) of the normal rim R. In this embodiment, in a normal pneumatic tire 1, the entire inner arcuate surface 12 (including the apex 11) contacts the rim flange Rf.

[0038] FIG. 3(A) is a cross-sectional perspective view of the right half of a tire 1. As shown in FIG. 3(A), in this embodiment, the rim protector 10 extends continuously and without interruption in the tire circumferential direction. FIG. 3(B) is a cross-sectional perspective view of the right half of a tire 1 in another embodiment. As shown in FIG. 3(B), the rim protector 10 may be provided so that it is interrupted in the tire circumferential direction. In this case, the total length La of the rim protector 10 in the tire circumferential direction is preferably 50% or more of the circumferential length at the position where the apex 11 is provided, more preferably 70% or more, and even more preferably 90% or more.

[0039] FIG. 4 is a cross-sectional view of a first sidewall portion 3A and a first bead portion 4A of another embodiment. As shown in FIG. 4, in this embodiment, the outer surface 13 is formed so that its center 13c is located inside the tire. In this tire 1, in a tire meridian cross section in a normal state, the apex 11 and inner arcuate surface 12 of the rim protector 10 satisfy the above formula (1) when the separation distance H, the radius of curvature C, and the rubber hardness B are specified. In addition, it is desirable that the radius of curvature L of the outer surface 13 is the same as the radius of curvature L of the outer surface 13 shown in FIG. 2. However, the outer surface 13 is not limited to this form and may be formed, for example, as a straight line.

[0040] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and implemented in various ways. [Example]

[0041] A pneumatic tire having the basic structure shown in Figure 1 was prototyped based on the specifications in Table 1. The test tires were then tested for low rolling resistance and ride comfort. The test method and common specifications for each test tire are as follows: Tire size: 215 / 55R17 Rim size: 17 x 7J Internal pressure: 200kPa

[0042] <Low rolling performance> The low rolling resistance performance was evaluated in accordance with ECE R117-02 (ECE Regulation No. 117 Revision 2). The low rolling resistance performance was evaluated by running the test tire on a simulated road surface using an indoor drum tester and measuring the rolling resistance value. The evaluation was expressed as an index where the reciprocal of the rolling resistance value of Comparative Example 1 is set to 100. The higher the numerical value, the better the result, and a value of 95 or higher is considered a pass. Vertical load: 4.6kN Speed: 80km / h

[0043] <Ride comfort> The test tires were mounted on all wheels of the vehicle described below, and a test driver drove the vehicle on a test course with a dry asphalt road surface equipped with a single protrusion. The test driver then evaluated the magnitude of the shock when going over the single protrusion and the magnitude of the vibration during driving by using his senses. The results are shown as a score, with Comparative Example 1 being 100. The higher the score, the better the ride comfort performance. Vehicle: 2000cc domestic FF vehicle The test results are shown in Tables 1 and 2.

[0044] [Table 1]

[0045] [Table 2]

[0046] As a result of the test, it is understood that the tires of the Examples have a slight decrease in low rolling resistance performance compared to the tire of Comparative Example 1, but that the ride comfort performance is greatly improved in all examples. It is also understood that the tires of the Examples have a greatly improved low rolling resistance performance compared to the tire of Comparative Example 2. Therefore, it is understood that the tires of the Examples have, overall, suppressed a decrease in low rolling resistance performance and have a greatly improved ride comfort performance.

[0047] [Note] The present invention includes the following aspects.

[0048] [Invention 1] A pneumatic tire, A tread portion; a first bead portion in which a bead core is embedded; a cap rubber that forms the contact surface of the tread portion and has a rubber hardness of B (degrees), In a tire meridian cross section in a normal state in which the pneumatic tire is mounted on a normal rim and adjusted to a normal internal pressure and no load is applied, a rim protector having a peak protruding outward from the tire and extending in the tire circumferential direction is formed on an outer surface of the first bead portion; The rim protector is an inner arcuate surface having a curvature radius C (mm) that extends from the apex toward the inside in the tire radial direction and has a center outside the tire; When the distance H in the tire axial direction between the top and the tire radial line defining the rim width of the regular rim is Satisfy the following formula (1): Pneumatic tires. 12.8≦H×B / C≦93.5 …(1) [Invention 2] The pneumatic tire according to invention 1 further satisfies the following formula (2): 25.0≦H×B / C≦93.5 …(2) [Invention 3] A pneumatic tire according to invention 2, further satisfying the following formula (3): 25.0≦H×B / C≦61.0 …(3) [Invention 4] 4. The pneumatic tire according to any one of Inventions 1 to 3, wherein the radius of curvature C is 9.5 to 15.0 (mm). [Invention 5] 5. The pneumatic tire according to any one of inventions 1 to 4, wherein the rubber hardness B is 48 to 74 (degrees). [Invention 6] 6. The pneumatic tire according to any one of Inventions 1 to 5, wherein the separation distance H is 4.0 to 12.0 (mm). [Invention 7] The pneumatic tire according to any one of the first to sixth aspects of the present invention, wherein in the pneumatic tire in a normal state, a distance D in the tire radial direction from a bead base line to the inner end of the inner arcuate surface in the tire radial direction is 11.5 to 14.5 mm. [Invention 8] 8. The pneumatic tire according to any one of claims 1 to 7, wherein in the pneumatic tire in a normal state, 50% or more of the length of the inner arcuate surface of the rim protector contacts the rim flange of the normal rim. [Explanation of symbols]

[0049] 1 pneumatic tire 2C Cap rubber 4A First bead section 4s external surface 10 Rim Protector 11 Top 12 Inner arc surface 12c center R Genuine rim RL Tire Radial Line

Claims

1. A pneumatic tire, A tread portion; a first bead portion in which a bead core is embedded; a cap rubber that forms the contact surface of the tread portion and has a rubber hardness of B (degrees), In a tire meridian cross section in a normal state in which the pneumatic tire is mounted on a normal rim and adjusted to a normal internal pressure and no load is applied, a rim protector having a peak protruding outward from the tire and extending in the tire circumferential direction is formed on an outer surface of the first bead portion; The rim protector is an inner arcuate surface having a radius of curvature C (mm) extending inward in the tire radial direction from the apex and having a center outside the tire; When the distance H in the tire axial direction between the top and a line in the tire radial direction that defines the rim width of the regular rim is The following formula (1) is satisfied: Pneumatic tires. 12.8≦H×B / C≦93.5 ... (1)

2. The pneumatic tire according to claim 1, further satisfying the following formula (2): 25.0≦H×B / C≦93.5 ... (2)

3. The pneumatic tire according to claim 2, further satisfying the following formula (3): 25.0≦H×B / C≦61.0 ... (3)

4. 4. The pneumatic tire according to claim 1, wherein the radius of curvature C is 9.5 to 15.0 (mm).

5. 4. The pneumatic tire according to claim 1, wherein the rubber hardness B is 48 to 74 (degrees).

6. 4. The pneumatic tire according to claim 1, wherein the separation distance H is 4.0 to 12.0 (mm).

7. 4. The pneumatic tire according to claim 1, wherein in the pneumatic tire in a normal state, a distance D in the tire radial direction from a bead base line to an inner end of the inner arcuate surface in the tire radial direction is 11.5 to 14.5 (mm).

8. 4. The pneumatic tire according to claim 1, wherein, in the pneumatic tire in a normal state, 50% or more of the length of the inner arcuate surface of the rim protector contacts the rim flange of the normal rim.

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