Tire

Abstract

To provide a tire 2 that can suppress generation of peeling-off of a tread while suppressing increase in rolling resistance.SOLUTION: A tire 2 includes a tread 4 and a belt 20. An end BE of a base layer 34 of the tread 4 is positioned on an axial direction inner side of an end 20E of the belt 20. The tread 4 includes a plurality of circumferential grooves 30, and a plurality of land parts 32 are constituted by them. The plurality of land parts 32 include crown land parts 32c, shoulder land parts 32s and middle land parts 32m. A cap layer ratio ARc of the crown land part 32c is 1.5 or more and 3.5 or less. A cap layer ratio ARm of the middle land part 32m is equal to or more than the cap layer ratio ARc of the crown land part 32c. A cap layer ratio ARs of the shoulder land part 32s is larger than the cap layer ratio ARm of the middle land part 32m, and is 5.0 or more and 9.5 or less.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a tire. More specifically, the present invention relates to a tire mounted on a passenger car.

Background Art

[0002] In consideration of the environment, reduction of rolling resistance is required for tires mounted on vehicles. For this purpose, reducing the number of elements constituting the tire, reducing the thickness of the elements, and adopting rubber having a low loss tangent as the material constituting the elements are considered (for example, Patent Document 1 below). The tread of the tire comes into contact with the road surface. The cap layer wears out, and eventually the base layer is exposed. In extreme driving (for example, when the vehicle makes a sharp turn at high speed), the shoulder portion of the tire (specifically, the tread portion) also comes into contact with the road surface. In extreme driving, a large load acts on the shoulder portion. The base layer is more brittle than the cap layer. When the cap layer wears out and the base layer is exposed, there is a risk of tread peeling. Therefore, various measures are taken for the tire so that the tread does not peel off.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a tire capable of suppressing the occurrence of tread peeling while suppressing an increase in rolling resistance.

Means for Solving the Problems

[0005] A tire according to one aspect of the present invention includes a pair of beads, a carcass bridging between the pair of beads, a tread positioned radially outside of the carcass, and a belt positioned between the tread and the carcass. The tread includes a base layer and a cap layer covering the entire base layer. The cap layer is harder than the base layer. The loss tangent of the base layer at 70°C is lower than the loss tangent of the cap layer at 30°C. The end of the base layer is positioned axially inside the end of the belt. The belt includes an inner belt ply and an outer belt ply positioned radially outside of the inner belt ply. The end of the outer belt ply is positioned axially inside the end of the inner belt ply. The tread includes a tread pattern including a plurality of circumferential grooves, whereby a plurality of land portions arranged axially are formed on the tread. The plurality of land portions include a crown land portion positioned on the equator side, a shoulder land portion positioned on the tread end side, and a middle land portion positioned between the crown land portion and the shoulder land portion in a portion between the equator plane of the tire and the end of the tread. The ratio ARc of the cap layer in the crown land portion is represented by an average value of the ratio of the cap layer thickness to the base layer thickness in the crown land portion. The ratio ARm of the cap layer in the middle land portion is represented by an average value of the ratio of the cap layer thickness to the base layer thickness in the middle land portion. And the ratio ARs of the cap layer in the shoulder land portion is represented by an average value of the ratio of the cap layer thickness to the base layer thickness in the shoulder land portion. The cap layer ratio ARc of the crown land portion is 1.5 or more and 3.5 or less. The cap layer ratio ARm of the middle land portion is equal to or more than the cap layer ratio ARc of the crown land portion. The cap layer ratio ARs of the shoulder land portion is larger than the cap layer ratio ARm of the middle land portion and is 5.0 or more and 9.5 or less. [Effect of the Invention]

[0006] According to the present invention, a tire can be obtained that can suppress the occurrence of tread peeling while suppressing an increase in rolling resistance.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0008] The tire of the present invention is assembled on a rim. Air is filled inside the tire, and the internal pressure of the tire is adjusted. The tire assembled on the rim is also called a tire-rim assembly. The tire-rim assembly includes a rim and a tire assembled on this rim.

[0009] In the present invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in the normal state. The state where the tire is assembled on the normal rim, the internal pressure of the tire is adjusted to 250 kPa, and no load is applied to the tire is called the standard state.

[0010] In the present invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in the normal state. The dimensions and angles of each part in the meridian cross-section of the tire that cannot be measured with the tire mounted on the regular rim are measured on the cut surface of the tire obtained by cutting the tire along a plane including the rotation axis. In this measurement, the tire is set so that the distance between the left and right beads matches the distance between the beads in the tire mounted on the regular rim. Note that the structure of the tire that cannot be confirmed with the tire mounted on the regular rim is confirmed on the aforementioned cut surface.

[0011] The regular rim means the rim defined in the standard that the tire adheres to. The "Standard Rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims.

[0012] The regular internal pressure means the internal pressure defined in the standard that the tire adheres to. The "Maximum Air Pressure" in the JATMA standard, the "Maximum Value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures.

[0013] The regular load means the load defined in the standard that the tire adheres to. The "Maximum Load Capacity" in the JATMA standard, the "Maximum Value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are regular loads.

[0014] In the present invention, the "nominal section width" is the "nominal section width" included in the "Tire Designation" defined in JIS D4202 "Automobile Tires - Designation and Dimensions".

[0015] In the present invention, the load index (LI) is, for example, an index that represents, as an exponent, the maximum mass that can be loaded onto a tire under specified conditions, i.e., the maximum load capacity, as defined in the JATMA standard.

[0016] In the present invention, among the elements constituting the tire, the hardness of the elements made of crosslinked rubber is measured using a Type A durometer under temperature conditions of 23°C in accordance with the provisions of JIS K6253.

[0017] In the present invention, among the elements constituting the tire, the loss tangent (tanδ) of the elements made of crosslinked rubber is measured using a viscoelastic spectrometer in accordance with the provisions of JIS K6394. The measurement conditions are as follows. Initial strain = 10% Dynamic strain = ±1% Frequency = 10 Hz Mode = elongation mode Temperature = 30°C or 70°C In this measurement, the test piece (length 40 mm × width 4 mm × thickness 1 mm) is sampled from the tire. The longitudinal direction of the test piece is made to coincide with the circumferential direction of the tire. When it is not possible to sample the test piece from the tire, the test piece is sampled from a sheet-like crosslinked rubber (hereinafter also referred to as a rubber sheet) obtained by pressurizing and heating the rubber composition used to form the element to be measured at a temperature of 170°C for 12 minutes.

[0018] In the present invention, the tread portion of the tire is the portion of the tire that contacts the road surface. The bead portion is the portion of the tire that is fitted to the rim. The sidewall portion is the portion of the tire that bridges between the tread portion and the bead portion. The tire includes, as parts, a tread portion, a pair of bead portions, and a pair of sidewall portions. The end portion of the tread portion is also called the shoulder portion. The portion of the equatorial plane of the tread portion, i.e., the central portion, is also called the crown portion.

[0019] [Findings on which the present invention is based] FIG. 8 shows a part of a conventional tire 2a. The tread 4a of this tire 2a includes a cap layer 36a and a base layer 34a. As shown in FIG. 8, the end BEa of the base layer 34a coincides with the end CEa of the cap layer 36a.

[0020] FIG. 9 shows the shoulder portion of another conventional tire 2b. In this tire 2b, the end BEb of the base layer 34b is located axially inside the end CEb of the cap layer 36b. In this tire 2b, the cap layer 36b covering the portion of the end BEb of the base layer 34b is thick compared to the tire 2a shown in FIG. 8. In the shoulder portion, the base layer 34b of this tire 2b is less likely to be exposed compared to the base layer 34a of the tire 2a shown in FIG. 8. The tread 4b of this tire 2b is less likely to peel compared to the tread 4a of the tire 2a.

[0021] Due to environmental considerations, the popularity of electric vehicles is increasing. Electric vehicles are equipped with batteries. Batteries that can travel a distance of around 500 km are heavy. Therefore, electric vehicles tend to be heavier than conventional gasoline vehicles. A higher load acts on the tires installed on electric vehicles compared to the tires installed on gasoline vehicles. As described above, the tread 4b of the tire 2b shown in FIG. 9 is less likely to peel compared to the tread 4a of the tire 2a shown in FIG. 8. However, since electric vehicles are heavier than conventional gasoline vehicles, there is still a risk of the tread 4b peeling even in the tire 2b with tread peeling countermeasures. Therefore, the inventor considered the installation on electric vehicles and studied a technique that can suppress tread peeling while minimizing the impact on other performances (for example, rolling resistance), and completed the invention described below.

[0022] [Summary of Embodiments of the Present Invention] The present invention is a tire including a pair of beads, a carcass bridging between the pair of beads, a tread located radially outside of the carcass, and a belt located between the tread and the carcass, The tread includes a base layer and a cap layer covering the entire base layer, the cap layer is harder than the base layer, the loss tangent of the base layer at 70 °C is lower than the loss tangent of the cap layer at 30 °C, the end of the base layer is located axially inside the end of the belt, the belt includes an inner belt ply and an outer belt ply located radially outside the inner belt ply, the end of the outer belt ply is located axially inside the end of the inner belt ply, the tread includes a tread pattern including a plurality of circumferential grooves, whereby a plurality of land portions arranged axially are formed on the tread, the plurality of land portions include a crown land portion located on the crown side, a shoulder land portion located on the tread end side, and a middle land portion located between the crown land portion and the shoulder land portion in a portion between the equatorial plane of the tire and the end of the tread, the ratio ARc of the cap layer in the crown land portion is represented by the average value of the ratio of the cap layer thickness to the base layer thickness in the crown land portion, the ratio ARm of the cap layer in the middle land portion is represented by the average value of the ratio of the cap layer thickness to the base layer thickness in the middle land portion, the ratio ARs of the cap layer in the shoulder land portion is represented by the average value of the ratio of the cap layer thickness to the base layer thickness in the shoulder land portion, the cap layer ratio ARc of the crown land portion is 1.5 or more and 3.5 or less, the cap layer ratio ARm of the middle land portion is equal to or more than the cap layer ratio ARc of the crown land portion, the cap layer ratio ARs of the shoulder land portion is larger than the cap layer ratio ARm of the middle land portion and is 5.0 or more and 9.5 or less, a tire.

[0023] The tire of the present invention can suppress the occurrence of tread separation while suppressing an increase in rolling resistance. The mechanism by which such an effect is achieved has not been clearly elucidated, but is presumed as follows.

[0024] In this tire, the end of the base layer is located axially inward of the end of the belt. In this tire, the cap layer covering the end portion of the base layer is thicker than that of conventional tires. In the shoulder portion, the base layer is less likely to be exposed. In limit running where a large load acts on the shoulder portion, the tread is less likely to separate. In this tire, the ratio of the base layer in the shoulder land portion is low. The cap layer is harder than the base layer. Therefore, there is a concern that problems such as an increase in rolling resistance, a deterioration in ride comfort, an increase in road noise, and a decrease in quietness may occur. However, in this tire, the cap layer ratio ARc in the crown land portion is 1.5 or more and 3.5 or less, the cap layer ratio ARm in the middle land portion is equal to or more than the cap layer ratio ARc in the crown land portion, and the cap layer ratio ARs in the shoulder land portion is larger than the cap layer ratio ARm in the middle land portion and is 5.0 or more and 9.5 or less. In other words, the ratio of the base layer occupying the land portion is low in the shoulder land portion and high in the crown land portion and the middle land portion. The base layer is softer than the cap layer and less likely to generate heat. The crown land portion and the middle land portion with a high base layer ratio can contribute to suppressing an increase in rolling resistance, a deterioration in ride comfort, and a decrease in quietness. This tire can suppress the occurrence of tread separation while suppressing an increase in rolling resistance, a deterioration in ride comfort, and a decrease in quietness.

[0025] Preferably, the position of the end of the cap layer coincides with the position of the end of the belt in the axial direction, or the end of the cap layer is located axially outside the end of the belt. In this case, the end of the base layer is covered with a cap layer having a sufficient thickness. In the shoulder portion, the base layer is less likely to be exposed. In limit running where a large load acts on the shoulder portion, the tread is less likely to separate. This tire can effectively suppress the occurrence of tread separation.

[0026] Preferably, the tire is mounted on a standard rim, the internal pressure of the tire is adjusted to 250 kPa, the camber angle of the tire is set to 0 degrees, a vertical load is applied to the tire, and the contact surface obtained by bringing the tire into contact with a flat road surface is the standard contact surface. The vertical load applied to the tire is 60% or more and 80% or less of the load indicated by the load index of the tire. The contact width of the standard contact surface is 70% or more and 80% or less of the nominal section width of the tire. The ratio of the total groove width of the plurality of circumferential grooves included in the standard contact surface to the contact width of the standard contact surface is 20% or more and 30% or less. In this case, responsiveness, ride comfort, and quietness are well balanced. This tire can suppress the occurrence of tread separation while suppressing an increase in rolling resistance, a decrease in responsiveness, a decrease in ride comfort, and a decrease in quietness.

[0027] Preferably, the tread pattern includes four circumferential grooves, and thus five land portions are formed in the tread. The five land portions are a crown land portion located on the equatorial plane, a pair of middle land portions located axially outside the crown land portion, and a pair of shoulder land portions located axially outside each middle land portion. The ratio of the width of the crown land portion to the contact width of the standard contact surface is 14% or more and 16% or less. In this case, a crown land portion having an appropriate width is formed. In a four-wheel vehicle (for example, a passenger car) equipped with this tire, a higher cornering force is generated in the front tire than in a conventional tire. This tire can effectively suppress an increase in rolling resistance and the occurrence of tread separation while suppressing a decrease in responsiveness.

[0028] Preferably, of the two ends of the tread, one end disposed on the inner side in the vehicle width direction by mounting the tire on the vehicle is the first reference end, and the other end is the second reference end. The width of the shoulder land portion on the first reference end side is 90% or more and 100% or less of the width of the crown land portion, the width of the middle land portion on the first reference end side is 90% or more and 100% or less of the width of the crown land portion, the width of the middle land portion on the second reference end side is 97% or more and 107% or less of the width of the crown land portion, and the width of the shoulder land portion on the second reference end side is 114% or more and 124% or less of the width of the crown land portion. In this case, compared with the conventional tire, the ratio of the cornering force in the rear tire to the cornering force in the front tire is effectively increased with respect to the cornering force in the front tire. This tire can effectively suppress an increase in rolling resistance and the occurrence of tread separation while improving linearity.

[0029] Preferably, in the crown land portion, the first reference end side with respect to the equatorial plane is the first part, and the second reference end side is the second part, and the ratio of the width of the second part to the width of the crown land portion is 51% or more and 55% or less. In this case, compared with the conventional tire, this tire can effectively increase the ratio of the cornering force in the rear tire to the cornering force in the front tire while effectively increasing the cornering force generated in the front tire. This tire can effectively suppress an increase in rolling resistance and the occurrence of tread separation while improving responsiveness and linearity.

[0030] [Details of Embodiments of the Present Invention] Hereinafter, the present invention will be described in detail based on preferred embodiments while appropriately referring to the drawings.

[0031] FIG. 1 shows a part of a tire 2 according to an embodiment of the present invention. This tire 2 is a pneumatic tire for a passenger car. The tire 2 in FIG. 1 is new. The tread 4 is not worn.

[0032] FIG. 1 shows a partial cross-section of this tire 2 along a plane including the rotation axis (not shown) of the tire 2. The cross-section shown in FIG. 1 is also called a meridian cross-section. The direction indicated by the double arrow AD is the axial direction of the tire 2. The axial direction of the tire 2 means a direction parallel to the rotation axis of the tire 2. The direction indicated by the double arrow RD is the radial direction of the tire 2. The direction perpendicular to the plane of FIG. 1 is the circumferential direction of the tire 2. In FIG. 1, the one-dot chain line EL extending in the radial direction represents the equatorial plane of the tire 2.

[0033] In FIG. 1, the tire 2 is mounted on the rim R. For example, air is filled between the tire 2 and the rim R, and the internal pressure of the tire 2 is adjusted. The rim R is a standard rim.

[0034] In FIG. 1, the solid line BBL extending in the axial direction is the bead base line. This bead base line is a line that defines the rim diameter of the rim R (refer to JATMA, etc.).

[0035] In FIG. 1, the position indicated by the symbol Eq is the intersection of the outer surface 2G of the tire 2 (specifically, the tread surface described later) and the equatorial plane. The intersection Eq is the equator of the tire 2. When a groove is located on the equatorial plane, the equator Eq is specified based on a virtual outer surface obtained by assuming that there are no irregularities such as grooves. The equator Eq is the radially outer end of the tire 2.

[0036] In FIG. 1, the position indicated by the symbol PW is the axial outer end of the tire 2 (hereinafter, the outer end PW). When there are decorations such as patterns and letters on the outer surface, the outer end PW is specified based on a virtual outer surface obtained by assuming that there are no decorations. The axial distance from one outer end PW to the other outer end PW specified in the tire 2 in the normal state is the cross-sectional width of the tire 2 (refer to JATMA, etc.).

[0037] In the present invention, the "designated section width" is used, and this "designated section width" means the "designated section width" included in the "tire designation" defined in JIS D4202 "Automobile Tires - Designation and Dimensions". For example, when the tire size specified in the "tire designation" of tire 2 is 245 / 50R19, the designated section width of this tire 2 is 245 mm. The designated section width of the tire targeted by the present invention (i.e., tire 2) is 215 mm or more and 325 mm or less. The load index (LI) of this tire 2 is 90 or more.

[0038] This tire 2 includes a tread 4, a pair of sidewalls 6, a pair of wings 8, a pair of clinches 10, a pair of beads 12, a carcass 14, an inner liner 16, a pair of chafers 18, a belt 20, and a band 22.

[0039] The tread 4 is located on the radially outer side of the carcass 14. The tread 4 is made of crosslinked rubber. The position indicated by the symbol Te in FIG. 1 is the end of the tread 4. In the present invention, among the two ends Te of the tread 4, one end Te that is arranged on the inner side in the vehicle width direction by mounting the tire 2 on a vehicle (not shown) is the first reference end Te1, and the other end Te is the second reference end Te2. In FIG. 1, the end Te of the tread 4 located on the arrow AD1 side is the first reference end Te1, and it is arranged on the inner side in the vehicle width direction by mounting the tire 2 on the vehicle. Although not shown, the end Te of the tread located on the arrow AD2 side is the second reference end Te2, and it is arranged on the outer side in the vehicle width direction by mounting the tire 2 on the vehicle.

[0040] The tread 4 contacts the road surface at the tread surface 24. The tread 4 has a tread surface 24. A side surface 26 is continuous with the tread surface 24. The outer surface 2G of the tire 2 includes the tread surface 24 and a pair of side surfaces 26. The tread surface 24 includes the equator Eq, and each side surface 26 includes the maximum width position PW.

[0041] Although not described in detail, the contour of the tread surface 24 in the meridian cross-section is represented by the contour of a virtual tread surface obtained by assuming that there are no irregularities such as grooves. The contour of the tread surface 24, that is, the contour of the virtual tread surface, includes a plurality of arcs, and these are combined so that adjacent arcs are in contact with each other. Among the plurality of arcs that make up the contour of the tread surface 24, the arc located outermost in the axial direction has the smallest radius. The side surface 26 is continuous with the arc having this smallest radius.

[0042] Grooves 28 are engraved in the tread 4. Thereby, a tread pattern is formed. The tread pattern includes a plurality of circumferential grooves 30 extending continuously in the circumferential direction. Thereby, a plurality of land portions 32 arranged in the axial direction are formed on the tread 4. The land surfaces of the land portions 32 are included in the tread surface 24.

[0043] FIG. 2 is a developed view showing a part of the tread surface 24. The direction indicated by the double-headed arrow AD is the axial direction of the tire 2. The direction indicated by the double-headed arrow CD is the circumferential direction of the tire 2. In FIG. 2, the direction indicated by the arrow AD1 is the first reference end Te1 side, and the direction indicated by the arrow AD2 is the second reference end Te2 side. In this FIG. 2, for the sake of convenience of explanation, grooves other than the circumferential grooves 30 are not shown. The tread 4 of this tire 2 is not limited to the tread 4 in which only the circumferential grooves 30 are engraved. Transverse grooves extending substantially in the axial direction or sipes may be engraved in this tread 4.

[0044] The tread pattern of this tire 2 includes four circumferential grooves 30 arranged in the axial direction. The groove depth of each circumferential groove 30 is 5.0 mm or more and 7.5 mm. The groove width of the circumferential groove 30 is 5.0 mm or more and 20.0 mm or less.

[0045] Of the four circumferential grooves 30, the two circumferential grooves 30 located outermost axially are shoulder circumferential grooves 30s. The two circumferential grooves 30 located axially inside the shoulder circumferential grooves 30s are middle circumferential grooves 30m. The tread pattern of this tire 2 includes a pair of shoulder circumferential grooves 30s and a pair of middle circumferential grooves 30m located between the pair of shoulder circumferential grooves 30s. In this tire 2, at least one circumferential groove may be further provided between the pair of middle circumferential grooves 30m.

[0046] In this tire 2, of the two middle circumferential grooves 30m, the middle circumferential groove 30m located on the first reference end Te1 side is the first middle circumferential groove 30m1, and the middle circumferential groove 30m located on the second reference end Te2 side is the second middle circumferential groove 30m2. Of the two shoulder circumferential grooves 30s, the shoulder circumferential groove 30s located on the first reference end Te1 side is the first shoulder circumferential groove 30s1, and the shoulder circumferential groove 30s located on the second reference end Te2 side is the second shoulder circumferential groove 30s2.

[0047] As described above, the tread pattern of this tire 2 includes four circumferential grooves 30 arranged axially. Thereby, five land portions 32 extending in the circumferential direction are formed. The edges of the circumferential grooves 30 are also the edges of the land portions 32. Of the five land portions 32 arranged axially, the two land portions 32 located outermost are shoulder land portions 32s. The shoulder land portions 32s include the grounding ends SEs of the standard ground contact surface described later. The two land portions 32 located axially inside the shoulder land portions 32s are middle land portions 32m. The land portion 32 located between the two middle land portions 32m is the crown land portion 32c. The crown land portion 32c of this tire 2 includes the equator Eq. In this tread pattern, the four circumferential grooves 30 are arranged symmetrically with respect to the equatorial plane. Therefore, the five land portions 32 are also arranged symmetrically with respect to the equatorial plane.

[0048] The five land portions 32 formed on this tread 4 are a crown land portion 32c located on the equatorial plane, a pair of middle land portions 32m located axially outside the crown land portion 32c, and a pair of shoulder land portions 32s located axially outside each middle land portion 32m. As shown in FIG. 1, in this tire 2, among the plurality of land portions 32, in the portion between the equatorial plane and the end Te of the tread 4, there are a crown land portion 32c located on the equatorial plane side, a shoulder land portion 32s located on the end Te side of the tread 4, and a middle land portion 32m located between the crown land portion 32c and the shoulder land portion 32s. Although not shown, for example, one circumferential groove 30 may be further provided between a pair of middle circumferential grooves 30m to form two crown land portions 32c. In this case, the circumferential groove 30 located between the two crown land portions 32c is also called a crown circumferential groove. Even in this case, among the plurality of land portions 32 formed on the tread 4, in the portion between the equatorial plane and the end Te of the tread 4, there are a crown land portion 32c located on the equatorial plane side, a shoulder land portion 32s located on the end Te side of the tread 4, and a middle land portion 32m located between the crown land portion 32c and the shoulder land portion 32s. The crown land portion 32c does not include the equator Eq, but the crown circumferential groove is located on the equatorial plane.

[0049] In this tire 2, among the two middle land portions 32m, the middle land portion 32m located on the first reference end Te1 side is the first middle land portion 32m1, and the middle land portion 32m located on the second reference end Te2 side is the second middle land portion 32m2. Among the two shoulder land portions 32s, the shoulder land portion 32s located on the first reference end Te1 side is the first shoulder land portion 32s1, and the shoulder land portion 32s located on the second reference end Te2 side is the second shoulder land portion 32s2.

[0050] The width of the land portion 32 formed on the tread 4, excluding the shoulder land portion 32s, is represented by the axial distance from one edge to the other edge of the land portion 32. The width of the shoulder land portion 32s is represented by the axial distance from the edge on the equatorial plane side of the shoulder land portion 32s to the grounding end SEs of the standard ground contact surface. When the edge of the land portion 32 is formed with chamfers such as rounding, the width of the land portion 32 is represented by taking the intersection of the extension line of the land surface of the land portion 32 and the extension line of the wall surface of the land portion 32 as the edge of the land portion 32. The extension line of the land surface is the contour of the tread surface 24. The extension line of the wall surface is represented by the tangent line of the wall surface with the boundary between the wall surface and the chamfered portion as the contact point.

[0051] In FIG. 3, the length indicated by the double arrow WC is the width of the crown land portion 32c. In this tire 2, the equatorial plane intersects the crown land portion 32c at the center of the width WC of the crown land portion 32c. In FIG. 3, the length indicated by the double arrow WM1 is the width of the first middle land portion 32m1. The length indicated by the double arrow WM2 is the width of the second middle land portion 32m2. In this tire 2, the width WM1 of the first middle land portion 32m1 is the same as the width WM2 of the second middle land portion 32m2. In FIG. 3, the length indicated by the double arrow WS1 is the width of the first shoulder land portion 32s1. The length indicated by the double arrow WS2 is the width of the second shoulder land portion 32s2. In this tire 2, the width WS1 of the first shoulder land portion 32s1 is the same as the width WS2 of the second shoulder land portion 32s2.

[0052] FIG. 3 schematically shows the ground contact shape of the tire 2. In FIG. 3, the direction indicated by the double arrow ADe corresponds to the axial direction of the tire 2. The direction indicated by the double arrow CDe corresponds to the circumferential direction of the tire 2. In FIG. 3, the direction indicated by the arrow ADe1 is the first reference end Te1 side, and the direction indicated by the arrow ADe2 is the second reference end Te2 side.

[0053] The ground contact surface is obtained, for example, using a ground contact surface shape measuring device (not shown). In this device, the tire 2 is mounted on the rim R, the internal pressure of the tire 2 is adjusted, a vertical load is applied to the tire 2, and the tire 2 is brought into contact with a road surface composed of a plane. When obtaining the ground contact surface, the tire 2 is arranged such that its rotation axis is parallel to the road surface. The aforementioned vertical load is applied to this tire 2 in a direction perpendicular to the road surface. In other words, the vertical load is applied to the tire 2 with the camber angle of the tire 2 set to 0°. Although not described in detail, an image of the contact surface formed by the tire 2 contacting a flat surface is obtained by a known method. Based on the obtained image, the contour of the contact surface is specified. The contour of the contact surface, that is, the contact surface shape of the contact surface, is obtained by tracing the periphery of the contact surface in the image of the contact surface.

[0054] In the present invention, the tire 2 is mounted on a standard rim, the internal pressure of the tire is adjusted to 250 kPa, the camber angle of the tire 2 is set to 0 degrees, a vertical load is applied to the tire 2, and the contact surface obtained by bringing the tire into contact with a road surface composed of a flat surface is the standard contact surface. When obtaining the standard contact surface, the vertical load applied to the tire 2 is 60% or more and 80% or less of the load indicated by the load index of this tire 2.

[0055] In FIG. 3, the position indicated by the reference symbol SEs is the grounding end of the standard contact surface. Of the two grounding ends SEs, the grounding end SEs located on the arrow ADe1 side is the first grounding end SEs1, and the grounding end SEs located on the arrow ADe2 side is the second grounding end SEs2. The first grounding end SEs1 side corresponds to the aforementioned first reference end Te1 side, and the second grounding end SEs2 side corresponds to the aforementioned second reference end Te2 side.

[0056] As shown in FIG. 3, the standard contact surface includes contact surfaces corresponding to the land portions 32, specifically, the crown land portion 32c, the two middle land portions 32m, and the two shoulder land portions 32s. The space between two adjacent contact surfaces corresponding to the land portions 32 corresponds to the circumferential groove 30. Therefore, the standard contact surface includes a plurality of circumferential grooves 30, specifically, two middle circumferential grooves 30m and two shoulder circumferential grooves 30s.

[0057] The tread 4 includes a base layer 34 and a cap layer 36. The tread 4 of this tire 2 is composed of the base layer 34 and the cap layer 36 arranged in the radial direction. As shown in FIG. 1, the base layer 34 is laminated on the band 22. The entire base layer 34 is covered with the cap layer 36. The base layer 34 is made of a low heat-generating crosslinked rubber. The cap layer 36 is located radially outside the base layer 34. The cap layer 36 includes the aforementioned tread surface 24. The cap layer 36 contacts the road surface. The cap layer 36 is made of crosslinked rubber considering wear resistance and grip performance.

[0058] In FIG. 1, the position indicated by the reference sign BE is the end of the base layer 34. The length indicated by the double arrow WTB is the width of the base layer 34. The width WTB of the base layer 34 is the axial distance from one end BE to the other end BE of the base layer 34. The position indicated by the reference sign CE is the end of the cap layer 36. The length indicated by the double arrow WTC is the width of the cap layer 36. The width WTC of the cap layer 36 is the axial distance from one end CE to the other end CE of the cap layer 36. In this tire 2, the end CE of the cap layer 36 is located axially outside the end BE of the base layer 34. The width WTC of the cap layer 36 is wider than the width WTB of the base layer 34. The end CE of the cap layer 36 is the end Te of the tread 4. The width of the tread 4 is represented by the width WTC of the cap layer 36.

[0059] In this tire 2, the cap layer 36 is harder than the base layer 34. Specifically, the hardness of the cap layer 36 is 60 or more and 70 or less, and the hardness of the base layer 34 is 50 or more and 65 or less. The difference between the hardness of the cap layer 36 and the hardness of the base layer 34 is 10 or more and 20 or less.

[0060] The measurement temperature of the loss tangent of the base layer 34 is 70°C. The loss tangent of the base layer 34 at 70°C is 0.02 or more and 0.10 or less. The measurement temperature of the loss tangent of the cap layer 36 is 30°C. The loss tangent of the cap layer 36 at 30°C is 0.12 or more and 0.40 or less. The loss tangent of the base layer 34 at 70°C is lower than the loss tangent of the cap layer 36 at 30°C. The loss tangent of the base layer 34 at 30°C is 0.10 or more and 0.38 or less of the loss tangent of the cap layer 36 at 70°C.

[0061] Each sidewall 6 is located radially inside the tread 4. The sidewall 6 is located axially outside the carcass 14. The sidewall 6 includes the aforementioned maximum width position PW. The sidewall 6 is made of crosslinked rubber considering cut resistance.

[0062] Each wing 8 is located between the tread 4 and the sidewall 6. The tread 4 and the sidewall 6 are joined via the wing 8. The wing 8 is made of crosslinked rubber considering adhesiveness.

[0063] Each clinch 10 is located radially inside the sidewall 6. The clinch 10 contacts the rim R. The clinch 10 is made of crosslinked rubber considering wear resistance.

[0064] Each bead 12 is located radially inside the sidewall 6. The bead 12 is located axially inside the clinch 10. The bead 12 includes a core 38 and an apex 40. The core 38 extends in the circumferential direction. Although not shown, the core 38 includes a steel wire. The apex 40 is located radially outside the core 38. The apex 40 tapers outward. The apex 40 is made of crosslinked rubber having high rigidity.

[0065] The carcass 14 is located inside the tread 4, the pair of sidewalls 6, and the pair of clinches 10. The carcass 14 spans between the pair of beads 12.

[0066] The carcass 14 includes at least one carcass ply 42. The carcass 14 of this tire 2 is composed of two carcass plies 42. Inside the tread 4, the carcass ply 42 located on the inner surface 2N side of the tire 2 is the first carcass ply 44, and the carcass ply 42 located outside the first carcass ply 44 is the second carcass ply 46.

[0067] As shown in FIG. 1, two carcass plies 42 are each folded from the axial inner side to the outer side by their respective beads 12. The end 44e of the first carcass ply 44 is located radially outside the maximum width position PW. The end 46e of the second carcass ply 46 is located between the apex 40 and the folded first carcass ply 44.

[0068] Although not shown, the carcass ply 42 includes a number of carcass cords arranged in parallel. These carcass cords intersect the equatorial plane. The carcass 14 of this tire 2 has a radial structure. In this tire 2, cords made of organic fibers are used as carcass cords. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.

[0069] The inner liner 16 is located inside the carcass 14. The inner liner 16 constitutes the inner surface 2N of the tire 2. The inner liner 16 is made of crosslinked rubber having excellent air barrier properties. The inner liner 16 retains the internal pressure of the tire 2.

[0070] Each chafer 18 is located radially inside the bead 12. The chafer 18 contacts the rim R. The chafer 18 of this tire 2 is composed of a cloth and rubber impregnated in this cloth. As shown in FIG. 1, the inner end of the chafer 18 constitutes a part of the inner surface 2N of the tire. The outer end of the chafer 18 is located radially outside its inner end. The outer end of the chafer 18 is located between the folded first carcass ply 44 and the clinch 10.

[0071] The belt 20 is located radially between the tread 4 and the carcass 14. The belt 20 is laminated on the carcass 14. The aforementioned equatorial plane intersects the belt 20 at the center of the width of the belt 20. Both ends 20e of the belt 20 are arranged to face each other across the equatorial plane.

[0072] The belt 20 includes a plurality of belt plies 48 arranged radially. Among the plurality of belt plies 48, the belt ply 48 located innermost is the inner belt ply 50, and the belt ply 48 located outermost is the outer belt ply 52. This belt 20 includes the inner belt ply 50 and the outer belt ply 52. The outer belt ply 52 is located radially outside the inner belt ply 50. The belt 20 of this tire 2 is composed of two belt plies 48. Specifically, this belt 20 is composed of an inner belt ply 50 and an outer belt ply 52. The inner belt ply 50 is laminated on the carcass 14 inside the tread 4 in the radial direction. The outer belt ply 52 is laminated on the inner belt ply 50.

[0073] In FIG. 1, the double-headed arrow WBU is the width of the inner belt ply 50. The width WBU of the inner belt ply 50 is the axial distance from one end 50e to the other end 50e of the inner belt ply 50. The double-headed arrow WBS is the width of the outer belt ply 52. The width WBS of the outer belt ply 52 is the axial distance from one end 52e to the other end 52e of the outer belt ply 52.

[0074] Although not shown, each of the plurality of belt plies 48 constituting the belt 20 includes a large number of belt cords arranged in parallel. The belt cords are steel cords. Each belt cord is inclined with respect to the equatorial plane. The direction of inclination of the belt cords included in the outer belt ply 52 is opposite to the direction of inclination of the belt cords included in the inner belt ply 50.

[0075] As shown in FIG. 1, the end 52e of the outer belt ply 52 is located axially inside the end 50e of the inner belt ply 50. The length from the end 52e of the outer belt ply 52 to the end 50e of the inner belt ply 50 is 3 mm or more and 10 mm or less. The width WBS of the outer belt ply 52 is narrower than the width WBU of the inner belt ply 50. In other words, the inner belt ply 50 is the widest belt ply 48 among the belt plies 48 that constitute the belt 20. The width of the belt 20 is represented by the width WBU of the wide inner belt ply 50. The end 50e of the inner belt ply 50 is the end 20e of the belt 20. In this tire 2, the width WBU of the inner belt ply 50, that is, the width WBU of the belt 20, is 40% or more and 65% or less of the nominal section width of this tire 2.

[0076] The band 22 is positioned between the tread 4 and the belt 20 in the radial direction. The end 22e of the band 22 is located axially inside the end Te of the tread 4. The entire band 22 is covered by the tread 4. The band 22 is laminated on the belt 20. The end 22e of the band 22 is located axially outside the end 20e of the belt 20. The length from the end 20e of the belt 20 to the end 22e of the band 22 is 3 mm or more and 7 mm or less. The aforementioned equatorial plane intersects the band 22 at the center of the width of the band 22. The both ends 22e of the band 22 are arranged to face each other across the equatorial plane. This band 22 is a full band. This band 22 may be a pair of edge bands configured to be axially spaced apart across the equatorial plane and cover the portion of the end 20e of the belt 20. This band 22 may be composed of a full band and a pair of edge bands.

[0077] Although not shown, the band 22 includes a band cord wound in a spiral shape. In the band 22, the band cord extends substantially in the circumferential direction. Specifically, the angle formed by the band cord with respect to the circumferential direction is 5° or less. The band 22 has a jointless structure. A cord made of organic fiber is used as the band cord. Examples of the organic fiber include nylon fiber, rayon fiber, polyester fiber, and aramid fiber.

[0078] As shown in FIG. 1, in the meridian cross section, the base layer 34 and the cap layer 36 that constitute the tread 4 extend in layers along the tread surface 24. In this tire 2, the thickness of each layer that constitutes the tread 4 is represented by the length along the normal line of the outer surface 2G of this tire 2 (specifically, the tread surface 24) in the meridian cross section of this tire 2. This normal line is specified based on the contour of the tread surface 24 and is also called the thickness reference line.

[0079] FIG. 4 shows a part of the tire 2 shown in FIG. 1. FIG. 4 shows a cross section of the crown land portion 32c. The position indicated by the symbol PCe is the edge of the crown land portion 32c. The edge PCe is the intersection of the extension line of the land surface, that is, the contour OL of the tread surface 24, and the extension line LCe of the wall surface. The straight line ECL is a line segment connecting the edge PCe on the first reference end Te1 side and the edge PCe on the second reference end Te2 side of the crown land portion 32c.

[0080] In FIG. 4, the straight lines LC1, LC2, and LC3 are the thickness reference lines in the crown land portion 32c. The symbols PC1, PC2, and PC3 are the positions that divide the line segment ECL connecting the edge PCe on the first reference end Te1 side and the edge PCe on the second reference end Te2 side of the crown land portion 32c into four equal parts. The thickness reference line LC1 passes through the position PC1, the thickness reference line LC2 passes through the position PC2, and the thickness reference line LC3 passes through the position PC3. The thickness reference line LC2 of this tire 2 coincides with the equatorial plane.

[0081] The length indicated by the double arrow CC1 along the thickness reference line LC1 is the thickness of the cap layer 36 at the position PC1. The length indicated by the double arrow BC1 is the thickness of the base layer 34 at the position PC1. The ratio CC1 / BC1 of the thickness CC1 of the cap layer 36 to the thickness BC1 of the base layer 34 is the cap layer thickness ratio ARc1 at the position PC1. The length indicated by the double arrow CC2 along the thickness reference line LC2 is the thickness of the cap layer 36 at the position PC2. The length indicated by the double arrow BC2 is the thickness of the base layer 34 at the position PC2. The ratio CC2 / BC2 of the thickness CC2 of the cap layer 36 to the thickness BC2 of the base layer 34 is the cap layer thickness ratio ARc2 at the position PC2. The length indicated by the double arrow CC3 along the thickness reference line LC3 is the thickness of the cap layer 36 at the position PC3. The length indicated by the double arrow BC3 is the thickness of the base layer 34 at the position PC3. The ratio CC3 / BC3 of the thickness CC3 of the cap layer 36 to the thickness BC3 of the base layer 34 is the cap layer thickness ratio ARc3 at the position PC3.

[0082] In this tire 2, the ratio ARc of the cap layer 36 occupying the crown land portion 32c is represented by the average value of the ratio CC / BC of the thickness CC of the cap layer to the thickness BC of the base layer in the crown land portion 32c. Specifically, the cap layer ratio ARc is represented by the average value of the cap layer thickness ratio CC1 / BC1 at the position PC1, the cap layer thickness ratio CC2 / BC2 at the position PC2, and the cap layer thickness ratio CC3 / BC3 at the position PC3.

[0083] FIG. 5 shows a part of the tire 2 shown in FIG. 1. FIG. 5 shows a cross section of the middle land portion 32m. The position indicated by the reference sign PMe is the edge of the middle land portion 32m. The edge PMe is the intersection of the extension line of the land surface, that is, the contour OL of the tread surface 24, and the extension line LMe of the wall surface. The straight line EML is a line segment connecting the edge PMe on the equatorial plane side of the middle land portion 32m and the edge PCe on the end Te side of the tread 4.

[0084] In FIG. 5, the straight lines LM1, LM2, and LM3 are thickness reference lines in the middle land portion 32m. The reference signs PM1, PM2, and PM3 are positions that divide the line segment EML connecting the edge PMe on the equatorial plane side of the middle land portion 32m and the edge PCe on the end Te side of the tread 4 into four equal parts. The thickness reference line LM1 passes through the position PM1, the thickness reference line LM2 passes through the position PM2, and the thickness reference line LM3 passes through the position PM3.

[0085] The length indicated by double arrows CM1 along the thickness reference line LM1 is the thickness of the cap layer 36 at the position PM1. The length indicated by double arrows BM1 is the thickness of the base layer 34 at the position PM1. The ratio CM1 / BM1 of the thickness CM1 of the cap layer 36 to the thickness BM1 of the base layer 34 is the cap layer thickness ratio ARm1 at the position PM1. The length indicated by double arrows CM2 along the thickness reference line LM2 is the thickness of the cap layer 36 at the position PM2. The length indicated by double arrows BM2 is the thickness of the base layer 34 at the position PM2. The ratio CM2 / BM2 of the thickness CM2 of the cap layer 36 to the thickness BM2 of the base layer 34 is the cap layer thickness ratio ARm2 at the position PM2. The length indicated by double arrows CM3 along the thickness reference line LM3 is the thickness of the cap layer 36 at the position PM3. The length indicated by double arrows BM3 is the thickness of the base layer 34 at the position PM3. The ratio CM3 / BM3 of the thickness CM3 of the cap layer 36 to the thickness BM3 of the base layer 34 is the cap layer thickness ratio ARm3 at the position PM3.

[0086] In this tire 2, the ratio ARm of the cap layer 36 occupying the middle land portion 32m is represented by the average value of the ratio CM / BM of the thickness CM of the cap layer to the thickness BM of the base layer in the middle land portion 32m. Specifically, the cap layer ratio ARm is represented by the average value of the cap layer thickness ratio CM1 / BM1 at the position PM1, the cap layer thickness ratio CM2 / BM2 at the position PM2, and the cap layer thickness ratio CM3 / BM3 at the position PM3.

[0087] FIG. 6 shows a part of the tire 2 shown in FIG. 1. FIG. 6 shows a cross-section of the shoulder land portion 32s. The position indicated by the symbol PSe is the edge of the shoulder land portion 32s. The edge PSe is the intersection of the extension line of the land surface, that is, the contour OL of the tread surface 24, and the extension line LSe of the wall surface. The straight line LB is the normal line of the tread surface 24 passing through the end 52e of the outer belt ply 52. The position indicated by the symbol PB is the intersection of the normal line LB and the tread surface 24. The intersection PB is the reference position that defines the thicknesses of the cap layer 36 and the base layer 34 in the shoulder land portion 32s. The straight line ESL is a line segment connecting the edge PSe of the shoulder land portion 32s and the reference position PB.

[0088] In FIG. 6, the straight lines LS1, LS2, and LS3 are thickness reference lines in the shoulder land portion 32s. The symbols PS1, PS2, and PS3 are the positions that divide the line segment ESL connecting the edge PSe of the shoulder land portion 32s and the reference position PB into four equal parts. The thickness reference line LS1 passes through the position PS1, the thickness reference line LS2 passes through the position PS2, and the thickness reference line LS3 passes through the position PS3.

[0089] The length indicated by the double arrow CS1 along the thickness reference line LS1 is the thickness of the cap layer 36 at the position PS1. The length indicated by the double arrow BS1 is the thickness of the base layer 34 at the position PS1. The ratio CS1 / BS1 of the thickness CS1 of the cap layer 36 to the thickness BS1 of the base layer 34 is the cap layer thickness ratio ARs1 at the position PS1. The length indicated by the double arrow CS2 along the thickness reference line LS2 is the thickness of the cap layer 36 at the position PS2. The length indicated by the double arrow BS2 is the thickness of the base layer 34 at the position PS2. The ratio CS2 / BS2 of the thickness CS2 of the cap layer 36 to the thickness BS2 of the base layer 34 is the cap layer thickness ratio ARs2 at the position PS2. The length indicated by the double arrows CS3 along the thickness reference line LS3 is the thickness of the cap layer 36 at the position PS3. The length indicated by the double arrows BS3 is the thickness of the base layer 34 at the position PS3. The ratio CS3 / BS3 of the thickness CS3 of the cap layer 36 to the thickness BS3 of the base layer 34 is the cap layer thickness ratio ARs3 at the position PS3.

[0090] In this tire 2, the ratio ARs of the cap layer 36 occupying the shoulder land portion 32s is represented by the average value of the ratio CS / BS of the thickness CS of the cap layer to the thickness BS of the base layer in the shoulder land portion 32s. Specifically, the cap layer ratio ARs is represented by the average value of the cap layer thickness ratio CS1 / BS1 at the position PS1, the cap layer thickness ratio CS2 / BS2 at the position PS2, and the cap layer thickness ratio CS3 / BS3 at the position PS3.

[0091] In this tire 2, the end BE of the base layer 34 is located axially inward of the end 20e of the belt 20. In this tire 2, compared with the conventional tire, the cap layer 36 covering the portion of the end BE of the base layer 34 is thick. The base layer 34 is less likely to be exposed in the shoulder portion. The tread 4 is less likely to peel off in the limit running where a large load acts on the shoulder portion.

[0092] In this tire 2, the ratio ARc of the cap layer 36 occupying the shoulder land portion 32s is higher than that of the conventional tire. In other words, the ratio of the base layer 34 occupying the shoulder land portion 32s is low. The cap layer 36 is harder and more likely to generate heat than the base layer 34. Therefore, there is a concern that things such as an increase in rolling resistance, a deterioration in riding comfort, an increase in road noise, and a decrease in quietness may occur. However, in this tire 2, the cap layer ratio ARc of the crown land portion 32c is 1.5 or more and 3.5 or less, the cap layer ratio ARm of the middle land portion 32m is equal to or more than the cap layer ratio ARc of the crown land portion 32c, and the cap layer ratio ARs of the shoulder land portion 32s is larger than the cap layer ratio ARm of the middle land portion 32m and is 5.0 or more and 9.5 or less. In other words, the ratio of the base layer 34 occupying the land portion 32 is low in the shoulder land portion 32s and high in the crown land portion 32c and the middle land portion 32m. The base layer 34 is softer than the cap layer 36 and less likely to generate heat. The crown land portion 32c and the middle land portion 32m with a high base layer ratio can contribute to suppressing an increase in rolling resistance, a deterioration in riding comfort, and a deterioration in quietness. This tire 2 can suppress the occurrence of tread separation while suppressing an increase in rolling resistance, a deterioration in riding comfort, and a deterioration in quietness.

[0093] From the viewpoint that the tire 2 can effectively suppress the occurrence of tread separation while suppressing an increase in rolling resistance, a deterioration in riding comfort, and a deterioration in quietness, the cap layer ratio ARc of the crown land portion 32c is preferably 2.0 or more and 3.0 or less. From the same viewpoint, the cap layer ratio ARm of the middle land portion 32m is preferably the same as the cap layer ratio ARc of the crown land portion 32c. From the same viewpoint, the cap layer ratio ARs of the shoulder land portion 32s is preferably 7.0 or more and 9.0 or less. More preferably, the cap layer ratio ARc of the crown land portion 32c is 2.0 or more and 3.0 or less, the cap layer ratio ARm of the middle land portion 32m is the same as the cap layer ratio ARc of the crown land portion 32c, and the cap layer ratio ARs of the shoulder land portion 32s is 7.0 or more and 9.0 or less.

[0094] Claim 2 For example, as shown in FIG. 1, the end CE of the cap layer 36 is located axially outside the end 50e of the inner belt ply 50, that is, the end 20e of the belt 20. The position of the end CE of the cap layer 36 may coincide with the position of the end 20e of the belt 20 in the axial direction. As described above, the end BE of the base layer 34 is located axially inside the end 20e of the belt 20. The end BE of the base layer 34 is covered with the cap layer 36 having a sufficient thickness. In the shoulder portion, the base layer 34 is less likely to be exposed. In the limit running where a large load acts on the shoulder portion, the tread 4 is less likely to peel off. This tire 2 can effectively suppress the occurrence of tread peeling. From this viewpoint, it is preferable that the position of the end CE of the cap layer 36 coincides with the position of the end 20e of the belt 20 in the axial direction, or the end CE of the cap layer 36 is located axially outside the end 20e of the belt 20, and it is more preferable that the end CE of the cap layer 36 is located axially outside the end 20e of the belt 20. From the same viewpoint, the ratio WTC / WBU of the width WTC of the cap layer 36 to the width WBU of the belt 20 is preferably 100% or more, and more preferably 103% or more. From the viewpoint that the volume of the cap layer 36 included in the shoulder land portion 32s is appropriately maintained and the influence on the ride comfort and quietness by the cap layer 36 included in the shoulder land portion 32s is effectively suppressed, the ratio WTC / WBU is preferably 110% or less, and more preferably 107% or less.

[0095] As described above, the end BE of the base layer 34 is located axially inside the end 20e of the belt 20. In this tire 2, the end BE of the base layer 34 is preferably located near the end 52e of the outer belt ply 52. Specifically, the ratio WTB / WBS of the width WTB of the base layer 34 to the width WBS of the outer belt ply 52 is preferably 90% or more and 110% or less. By setting the ratio WTB / WBS to 90% or more, the base layer 34 can effectively contribute to reducing the rolling resistance. Also, in the shoulder land portion 32s, the base layer 34 can contribute to suppressing a decrease in responsiveness, riding comfort, and quietness. From these viewpoints, the ratio WTB / WBS is more preferably 95% or more, and even more preferably 98% or more. By setting the ratio WTB / WBS to 110% or less, the edge BE of the base layer 34 is covered with the cap layer 36 having a sufficient thickness. This tire 2 can effectively suppress the occurrence of tread peeling. From this viewpoint, the ratio WTB / WBS is more preferably 105% or less, and even more preferably 102% or less.

[0096] For example, as shown in FIG. 6, in the shoulder land portion 32s, the base layer 34 tapers outward in the axial direction. The edge BE of the base layer 34 is covered with the cap layer 36 having a sufficient thickness. In the shoulder portion, the base layer 34 is less likely to be exposed. In the limit running where a large load acts on the shoulder portion, the tread 4 is less likely to peel off. This tire 2 can effectively suppress the occurrence of tread peeling. From this viewpoint, in the shoulder land portion 32s, it is preferable that the base layer 34 tapers outward in the axial direction. From a similar viewpoint, the cap layer thickness ratio ARs3 at the position PS3 is preferably 0.4 times or less, and more preferably 0.3 times or less, of the cap layer thickness ratio ARs1 at the position PS1. From the viewpoint that the base layer 34 can contribute to reducing the rolling resistance, the cap layer thickness ratio ARs3 at the position PS3 is preferably 0.1 times or more, and more preferably 0.2 times or more, of the cap layer thickness ratio ARs1 at the position PS1.

[0097] The length indicated by the double arrow CW in FIG. 3 is the grounding width of the standard ground contact surface. The grounding width CW is represented by the axial distance from the first grounding end SEs1 to the second grounding end SEs2. The one-dot chain line LPs is the grounding width center line of the standard ground contact surface. The length indicated by the double arrow CG, that is, the length of the intersection line of the standard ground contact surface and the grounding width center line LPs, is the grounding length at the center of the grounding width of the standard ground contact surface.

[0098] In this tire 2, the ground contact width CW of the standard ground contact surface is preferably 70% or more and 80% or less of the nominal section width of the tire 2. Thereby, the tire 2 can contact the road surface with sufficient width. In this tire 2, the decrease in responsiveness due to increasing the base layer ratio in the crown land portion 32c and the middle land portion 32m is effectively suppressed. This tire 2 can maintain good handling stability.

[0099] In FIG. 3, the double-headed arrow WGM is the groove width of the middle circumferential groove 30m in the standard ground contact surface. The double-headed arrow WGS is the groove width of the shoulder circumferential groove 30s in the standard ground contact surface. The solid line LA is a straight line passing through the center of the contact length CG and extending in the axial direction. The groove width WGM and the groove width WGS are measured along this straight line LA.

[0100] In this tire 2, the sum of the groove widths of the plurality of circumferential grooves 30 included in the standard ground contact surface, that is, the sum WGT of the groove width WGM of the two middle circumferential grooves 30m and the groove width WGS of the two shoulder circumferential grooves 30s included in the standard ground contact surface is adjusted. Specifically, the ratio (WGT / CW) of the sum WGT of the groove widths of the plurality of circumferential grooves 30 included in the standard ground contact surface to the ground contact width CW of the standard ground contact surface is preferably 20% or more and 30% or less. Thereby, in this tire 2, responsiveness, ride comfort, and quietness are well balanced. From this viewpoint, this ratio (WGT / CW) is more preferably 22% or more and 28% or less, and even more preferably 24% or more and 26% or less.

[0101] From the viewpoint that the tire 2 can suppress the occurrence of tread peeling while suppressing an increase in rolling resistance, a decrease in responsiveness, a decrease in ride comfort, and a decrease in quietness, the ground contact width CW of the standard ground contact surface is 70% or more and 80% or less of the nominal section width of the tire 2, and the ratio (WGT / CW) of the sum WGT of the groove widths of the plurality of circumferential grooves 30 included in the standard ground contact surface to the ground contact width CW of the standard ground contact surface is more preferably 20% or more and 30% or less.

[0102] Figure 7 shows a modified example of the tread pattern. Also in this Figure 7, similar to Figure 2, for the sake of convenience of explanation, only four circumferential grooves 30 are shown as the grooves 28 constituting the tread pattern. In Figure 7, the direction indicated by arrow AD1 is the first reference end Te1 side, and the direction indicated by arrow AD2 is the second reference end Te2 side.

[0103] In this tread pattern, the four circumferential grooves 30 are arranged asymmetrically with respect to the equatorial plane. Accordingly, the five land portions 32 are also arranged asymmetrically with respect to the equatorial plane.

[0104] In the tread pattern shown in Figure 7, the width WC of the crown land portion 32c is considered. Specifically, the crown land portion 32c is configured to have a width WC wider than the width WC of the crown land portion 32c shown in Figure 2. Thereby, in a vehicle equipped with this tire 2, a high cornering force is generated in the front tire. This tire 2 can contribute to suppressing the response delay of the front tire. This tire 2 can effectively suppress an increase in rolling resistance and the occurrence of tread peeling while suppressing a decrease in responsiveness. From this viewpoint, the ratio WC / CW of the width WC of the crown land portion 32c to the contact width CW of the standard contact surface is preferably 14% or more. The ratio WC / CW is preferably 16% or less. Thereby, in a vehicle equipped with this tire 2, a high cornering force is generated in a well-balanced manner in the front tire and the rear tire. This tire 2 can contribute to an improvement in linearity.

[0105] In this tire 2, the middle land portion 32m on the first reference end TE1 side (hereinafter referred to as the first middle land portion 32m1) has a groove width WM1 approximately the same as the groove width WS1 of the shoulder land portion 32s on the first reference end TE1 side (hereinafter referred to as the first shoulder land portion 32s1). The crown land portion 32c has a groove width WC approximately the same as the groove width WM1 of the first middle land portion 32m1, or has a groove width WC wider than the groove width WM1. The middle land portion 32m on the second reference end TE2 side (hereinafter referred to as the second middle land portion 32m2) has a groove width WM2 approximately the same as the width WC of the crown land portion 32c, or has a groove width WM2 wider than the groove width WC. The shoulder land portion 32s on the second reference end TE2 side (hereinafter referred to as the second shoulder land portion 32s2) has a groove width WS2 wider than the groove width WM2 of the second middle land portion 32m2. By adopting the tread pattern of FIG. 7, the ratio of the cornering force in the rear tire to the cornering force in the front tire can be effectively increased compared to conventional tires. When this tire 2 is mounted on a vehicle, the linearity is improved. This tire 2 can effectively suppress an increase in rolling resistance and the occurrence of tread separation while improving linearity, that is, while enhancing the handling stability of the vehicle.

[0106] The width WS1 of the first shoulder land portion 32s1 is preferably 90% or more and 100% or less of the width WC of the crown land portion 32c. By setting the width WS1 to 90% or more of the width WC, this tire 2 can configure the crown land portion 32c, the first middle land portion 32m1, and the second middle land portion 32m2 with appropriate widths. When this tire 2 is mounted on a vehicle, high cornering forces are generated in a well-balanced manner in the front and rear tires, so the linearity is improved. By setting the width WS1 to 100% or less of the width WC, this tire 2 can configure the crown land portion 32c, the first middle land portion 32m1, and the second middle land portion 32m2 with appropriate widths. When this tire 2 is mounted on a vehicle, a high cornering force is generated in the front tire, so the response delay of the front tire is suppressed.

[0107] The width WM1 of the first middle land portion 32m1 is preferably 90% or more and 100% or less of the width WC of the crown land portion 32c. When the width WM1 is set to 90% or more of the width WC, when this tire 2 is mounted on a vehicle, a high cornering force is generated in the front tire. This tire 2 can contribute to suppressing the response delay of the front tire. When the width WM1 is set to 100% or less of the width WC, when this tire 2 is mounted on a vehicle, a high cornering force is generated well-balancedly in the front tire and the rear tire. This tire 2 can contribute to improving linearity.

[0108] The width WM2 of the second middle land portion 32m2 is preferably 97% or more and 107% or less of the width WC of the crown land portion 32c. When the width WM2 is set to 97% or more of the width WC, when this tire 2 is mounted on a vehicle, a high cornering force is generated in the front tire. This tire 2 can contribute to suppressing the response delay of the front tire. When the width WM2 is set to 107% or less of the width WC, when this tire 2 is mounted on a vehicle, a high cornering force is generated well-balancedly in the front tire and the rear tire. This tire 2 can contribute to improving linearity.

[0109] The width WS2 of the second shoulder land portion 32s2 is preferably 114% or more and 124% or less of the width WC of the crown land portion 32c. When the width WS2 is set to 114% or more of the width WC, this tire 2 can configure the crown land portion 32c, the first middle land portion 32m1, and the second middle land portion 32m2 with appropriate widths. When this tire 2 is mounted on a vehicle, a high cornering force is generated well-balancedly in the front tire and the rear tire, so linearity is improved. By setting the width WS1 to 124% or less of the width WC, this tire 2 can configure the crown land portion 32c, the first middle land portion 32m1, and the second middle land portion 32m2 with appropriate widths. When this tire 2 is mounted on a vehicle, a high cornering force is generated in the front tire, so the response delay of the front tire is suppressed.

[0110] In the crown land portion 32c shown in FIG. 7, the center of its width is arranged on the second reference end Te2 side with respect to the equatorial plane. That is, when the crown land portion 32c is divided by the equatorial plane into a first portion 32c1 on the first reference end Te1 side and a second portion 32c2 on the second reference end Te2 side, the width of the second portion 32c2 is wider than the width of the first portion 32c1. Thereby, this tire 2 can effectively increase the cornering force generated in the front tire while effectively increasing the ratio of the cornering force of the rear tire to the cornering force of the front tire. This tire 2 can effectively suppress an increase in rolling resistance and the occurrence of tread separation while improving responsiveness and linearity.

[0111] In FIG. 7, the double-headed arrow W2 is the width of the second portion 32c2. This width W2 is represented by the axial distance from the equatorial plane to the edge of the crown land portion 32c on the second reference end Te2 side. From the viewpoint that the tire 2 can effectively suppress an increase in rolling resistance and the occurrence of tread separation while improving responsiveness and linearity, the ratio (W2 / WC) of the width W2 of the second portion 32c2 to the width WC of the crown land portion 32c is preferably 51% or more and 55% or less.

[0112] From the perspective that the tire 2 can effectively suppress an increase in rolling resistance and the occurrence of tread peeling while improving responsiveness and linearity, when the tread pattern of the tire 2 includes four circumferential grooves 30 and five land portions 32 are formed on the tread 4, it is preferable that the ratio WC / CW of the width WC of the crown land portion 32c to the contact width CW of the standard contact surface is 14% or more and 16% or less. In this case, the width WS1 of the shoulder land portion 32s1 on the first reference end Te1 side is 90% or more and 100% or less of the width WC of the crown land portion 32c, the width WM1 of the middle land portion 32m1 on the first reference end Te1 side is 90% or more and 100% or less of the width WC of the crown land portion 32c, the width WM2 of the middle land portion 32m2 on the second reference end Te2 side is 97% or more and 107% or less of the width WC of the crown land portion 32c, the width WS2 of the shoulder land portion 32s2 on the second reference end Te2 side is 114% or more and 124% or less of the width WC of the crown land portion 32c, and it is more preferable that the ratio of the width W2 of the second part 32c2 of the crown land portion 32c to the width WC of the crown land portion 32c is 51% or more and 55% or less. In particular, when the contact width CW of the standard contact surface is 70% or more and 80% or less of the nominal section width of the tire 2 and the ratio (WTG / CW) of the total groove width WGT of the plurality of circumferential grooves 30 included in the standard contact surface to the contact width CW of the standard contact surface is 20% or more and 30% or less, the tread pattern shown in FIG. 7 can effectively contribute to the improvement of responsiveness and linearity. This tire 2 can effectively suppress an increase in rolling resistance and the occurrence of tread peeling while improving responsiveness and linearity.

[0113] As is clear from the above description, according to the present invention, a tire can be obtained that can suppress the occurrence of tread peeling while suppressing an increase in rolling resistance. The present invention particularly exhibits a remarkable effect in tires having a nominal section width of 215 mm or more and 325 mm or less and a load index (LI) of 90 or more.

Examples

[0114] Hereinafter, the present invention will be described in more detail with reference to examples and the like, but the present invention is not limited to such examples only.

[0115] [Example 1] A tire (tire size = 245 / 50R19) having the basic configuration shown in FIG. 1 and having the specifications shown in Table 1 below was obtained. As shown in FIG. 6, the edge of the base layer was disposed near the edge of the outer belt ply. This is indicated by "FIG. 6" in the column of "CAP / BASE Structure" in the table. The ratio WTB / WBS of the width WTB of the base layer to the width WBS of the outer belt ply was 100%. The cap layer ratios ARc of the crown land, ARm of the middle land, and ARs of the shoulder land are as shown in Table 1 below. The four circumferential grooves provided in the tread were arranged as shown in FIG. 2. This is indicated by "FIG. 2" in the column of "Tread Pattern" in the table. The ratio WGT / CW of the total groove width WGT of the plurality of circumferential grooves included in the standard contact surface to the contact width CW of the standard contact surface, The ratio WS2 / WC of the width WS2 of the second shoulder land to the width WC of the crown land, The ratio WM2 / WC of the width WM2 of the second middle land to the width WC of the crown land, The ratio WM1 / WC of the width WM1 of the first middle land to the width WC of the crown land, The ratio WS1 / WC of the width WS1 of the first shoulder land to the width WC of the crown land, The ratio W2 / WC of the width W2 of the second part of the crown land to the width WC of the crown land, And the ratio WC / CW of the width WC of the crown land to the contact width CW of the standard contact surface is as shown in Table 1 below.

[0116] [Comparative Examples 1 and 2] Comparative Examples 1 and 2 are conventional tires (tire size = 245 / 50R19). The specifications of Comparative Examples 1 and 2 are as shown in Table 1 below.

[0117] [Example 2] The tire of Example 2 was obtained in the same manner as in Example 1, except that the circumferential groove arrangement was changed as shown in Fig. 7, and the ratios WGT / CW, WS2 / WC, WM2 / WC, WM1 / WC, WS1 / WC, W2 / WC, and WC / CW were made as shown in Table 1 below.

[0118] [Example 3] The tire of Example 3 was obtained in the same manner as in Example 2, except that the ratio WTB / WBS was made as shown in Table 1 below.

[0119] [Comparative Example 3-4] The tire of Comparative Example 3-4 was obtained in the same manner as in Example 2, except that the cap layer ratio ARc of the crown land was made as shown in Table 1 below.

[0120] [Example 4 and Comparative Example 5] The tires of Example 4 and Comparative Example 5 were obtained in the same manner as in Example 2, except that the cap layer ratio ARm of the middle land was made as shown in Table 2 below.

[0121] [Comparative Example 6-7] The tires of Comparative Example 6-7 were obtained in the same manner as in Example 2, except that the cap layer ratio ARs of the shoulder land was made as shown in Table 2 below.

[0122] [Example 5-12] The tires of Example 5-12 were obtained in the same manner as in Example 1, except that the ratios WS2 / WC, WM2 / WC, WM1 / WC, WS1 / WC, and WC / CW were made as shown in Tables 2 and 3 below.

[0123] [Rolling Resistance (RRC)] Using a rolling resistance tester, the rolling resistance coefficient (RRC) was measured when the prototype tire traveled on a drum at a speed of 80 km / h under the following conditions. The results are shown in the "RRC" column of Table 1-3 below with Comparative Example 1 as 100. The larger the value, the lower the rolling resistance of the tire. Rim: 7.5 inches Internal pressure: 250 kPa Vertical load: 7.26 kN

[0124] [Running test] The prototype tire was mounted on a rim (size = 7.5 inches), filled with air, and the internal pressure of the tire was adjusted to 250 kPa. The tire was mounted on a test vehicle (passenger car). The test vehicle was driven on a test course on a dry road surface, and a sensory evaluation regarding responsiveness and ride comfort was conducted. The results are shown in the columns of "Responsiveness" and "Ride comfort" in Table 1-3 below with the index taking Comparative Example 1 as 100. The larger the numerical value, the more the decrease in responsiveness or ride comfort is suppressed, and the better it is.

[0125] [Durability] Regarding the tire on which the above-mentioned running test was conducted, the appearance was observed, the occurrence situation of tread separation was confirmed, and the size (area) of the separated part was obtained. The results are shown in the column of "Durability" in Table 1-3 below with the index taking Comparative Example 1 as 100. The larger the numerical value, the more tread separation is suppressed.

[0126] [Quietness (road noise: R / N)] The prototype tire was mounted on a rim (size = 7.5 inches), filled with air, and the internal pressure of the tire was adjusted to 250 kPa. The tire was mounted on a test vehicle (front-wheel drive passenger car with a displacement of 2000 cc). The sound pressure level of the cavity resonance sound (road noise) when driving on a test course on a dry road surface at a speed of 30 km / h was collected with a microphone installed at the ear-allowing position on the driver's seat window side. The results are shown in the column of "R / N" in Table 1-3 below with the index taking Comparative Example 1 as 100. The larger the numerical value, the better it is. Note that the cavity resonance sound has a peak value at around 240 Hz.

[0127] [Quietness (pattern noise: P / N)] A prototype tire was mounted on a rim (size = 7.5 inches), filled with air, and the internal pressure of the tire was adjusted to 250 kPa. The tire was mounted on a test vehicle (a front-wheel drive passenger car with a displacement of 2000 cc). A sensory evaluation regarding the swishing sound was conducted when driving on a dry road test course at a speed of 100 km / h. The results are shown in the "P / N" column of Table 1-3 below with the comparative example 1 taken as 100. The larger the numerical value, the better.

[0128] [Overall Performance] The sum of the index values obtained in each evaluation was calculated. The results are shown in the "Overall" column of Table 1 below. The larger the numerical value, the more preferable.

[0129] [Table 1]

[0130] [Table 2]

[0131] [Table 3]

[0132] As shown in Table 1-3, in the examples, it has been confirmed that the occurrence of tread separation is suppressed while suppressing an increase in rolling resistance. From this evaluation result, the superiority of the present invention is clear. [Industrial Applicability]

[0133] The technology described above, which can suppress the occurrence of tread separation while suppressing an increase in rolling resistance, can be applied to various tires.

[0134] [Supplementary Note] The present invention includes the following aspects.

[0135] [1] A tire comprising a pair of beads, a carcass spanning between the pair of beads, a tread positioned radially outside of the carcass, and a belt positioned between the tread and the carcass, wherein the tread comprises a base layer and a cap layer covering the entire base layer, the cap layer is harder than the base layer, the loss tangent of the base layer at 70 °C is lower than the loss tangent of the cap layer at 30 °C, an end of the base layer is positioned axially inside an end of the belt, the belt comprises an inner belt ply and an outer belt ply positioned radially outside of the inner belt ply, an end of the outer belt ply is positioned axially inside an end of the inner belt ply, the tread comprises a tread pattern including a plurality of circumferential grooves, whereby a plurality of land portions arranged axially are formed on the tread, the plurality of land portions include a crown land portion positioned on the equator side, a shoulder land portion positioned on the tread end side, and a middle land portion positioned between the crown land portion and the shoulder land portion in a portion between the equator plane of the tire and the end of the tread, a ratio ARc of the cap layer in the crown land portion is represented by an average value of a ratio of the cap layer thickness to the base layer thickness in the crown land portion, a ratio ARm of the cap layer in the middle land portion is represented by an average value of a ratio of the cap layer thickness to the base layer thickness in the middle land portion, a ratio ARs of the cap layer in the shoulder land portion is represented by an average value of a ratio of the cap layer thickness to the base layer thickness in the shoulder land portion, the cap layer ratio ARc of the crown land portion is 1.5 or more and 3.5 or less, the cap layer ratio ARm of the middle land portion is equal to or more than the cap layer ratio ARc of the crown land portion, The cap layer ratio ARs of the shoulder land part is larger than the cap layer ratio ARm of the middle land part and is 5.0 or more and 9.5 or less. Tire. [2] The position of the end of the cap layer coincides with the position of the end of the belt in the axial direction, or the end of the cap layer is located outside the belt end in the axial direction. The tire according to [1] above. [3] Assemble the tire on a standard rim, adjust the internal pressure of the tire to 250 kPa, set the camber angle of the tire to 0 degrees, load a vertical load on the tire, and contact the tire with a flat road surface. The resulting contact patch is the standard contact patch. The vertical load applied to the tire is 60% or more and 80% or less of the load indicated by the load index of the tire. The contact width of the standard contact patch is 70% or more and 80% or less of the nominal section width of the tire. For the plurality of circumferential grooves included in the standard contact patch, the ratio of the total groove width to the contact width of the standard contact patch is 20% or more and 30% or less. The tire according to [1] or [2] above. [4] The tread pattern includes four circumferential grooves, whereby five land parts are formed in the tread. The five land parts are the crown land part located on the equatorial plane, a pair of middle land parts located outside the crown land part in the axial direction, and a pair of shoulder land parts located outside each middle land part in the axial direction. The ratio of the width of the crown land part to the contact width of the standard contact patch is 14% or more and 16% or less. The tire according to [3] above. [5] Of the two ends of the tread, one end disposed on the inner side in the vehicle width direction by mounting the tire on the vehicle is the first reference end, and the other end is the second reference end. The width of the shoulder land part on the first reference end side is 90% or more and 100% or less of the width of the crown land part. The width of the middle land part on the first reference end side is 90% or more and 100% or less of the width of the crown land part. The width of the middle land portion on the second reference end side is 97% or more and 107% or less of the width of the crown land portion, The width of the shoulder land portion on the second reference end side is 114% or more and 124% or less of the width of the crown land portion. The tire according to [4] above. [6] Among the crown land portions, the first reference end side with respect to the equatorial plane is the first part, and the second reference end side is the second part, The ratio of the width of the second part to the width of the crown land portion is 51% or more and 55% or less. The tire according to [4] or [5] above.

Explanation of symbols

[0136] 2 ··· Tire 4 ··· Tread 12 ··· Bead 14 ··· Carcass 20 ··· Belt 24 ··· Tread surface 30, 30s, 30m ··· Circumferential grooves 32, 32s, 32m, 32c ··· Land portions 32c1 ··· First part of the crown land portion 32c 32c2 ··· Second part of the crown land portion 32c 34 ··· Base layer 36 ··· Cap layer 48, 50, 52 ··· Belt plies

Claims

**Claim 1** A tire comprising a pair of beads, a carcass spanning between the pair of beads, a tread positioned radially outside of the carcass, and a belt positioned between the tread and the carcass, wherein the tread comprises a base layer and a cap layer covering the entire base layer, the cap layer is harder than the base layer, the loss tangent of the base layer at 70°C is lower than the loss tangent of the cap layer at 30°C, the end of the base layer is positioned axially inside the end of the belt, the belt comprises an inner belt ply and an outer belt ply positioned radially outside of the inner belt ply, the end of the outer belt ply is positioned axially inside the end of the inner belt ply, the tread comprises a tread pattern including a plurality of circumferential grooves, whereby a plurality of land portions arranged axially are formed on the tread, the plurality of land portions include a crown land portion positioned on the equator side, a shoulder land portion positioned on the tread end side, and a middle land portion positioned between the crown land portion and the shoulder land portion in a portion between the equatorial plane of the tire and the end of the tread, the ratio ARc of the cap layer in the crown land portion is represented by the average value of the ratio of the cap layer thickness to the base layer thickness in the crown land portion, the ratio ARm of the cap layer in the middle land portion is represented by the average value of the ratio of the cap layer thickness to the base layer thickness in the middle land portion, the ratio ARs of the cap layer in the shoulder land portion is represented by the average value of the ratio of the cap layer thickness to the base layer thickness in the shoulder land portion, the cap layer ratio ARc of the crown land portion is 1.5 or more and 3.5 or less, the cap layer ratio ARm of the middle land portion is equal to or more than the cap layer ratio ARc of the crown land portion, the cap layer ratio ARs of the shoulder land portion is larger than the cap layer ratio ARm of the middle land portion and is 5.0 or more and 9.5 or less, a tire. **Claim 2** The position of the end of the cap layer coincides with the position of the end of the belt in the axial direction, or the end of the cap layer is positioned axially outside the end of the belt, The tire according to claim 1. **Claim 3** Mount the tire on a standard rim, adjust the internal pressure of the tire to 250 kPa, set the camber angle of the tire to 0 degrees, load a vertical load on the tire, and bring the tire into contact with a flat road surface. The resulting contact surface is the standard contact surface. The vertical load applied to the tire is 60% or more and 80% or less of the load indicated by the load index of the tire. The contact width of the standard contact surface is 70% or more and 80% or less of the nominal section width of the tire. The ratio of the total groove width of the plurality of circumferential grooves included in the standard contact surface to the contact width of the standard contact surface is 20% or more and 30% or less. The tire according to claim 1.

4. The tread pattern includes four of the circumferential grooves, whereby five land portions are formed on the tread. The five land portions are the crown land portion located on the equatorial plane, a pair of middle land portions located axially outside the crown land portion, and a pair of shoulder land portions located axially outside each of the middle land portions. The ratio of the width of the crown land portion to the contact width of the standard contact surface is 14% or more and 16% or less. The tire according to claim 3.

5. Of the two ends of the tread, one end disposed on the inner side in the vehicle width direction when the tire is mounted on a vehicle is the first reference end, and the other end is the second reference end. The width of the shoulder land portion on the first reference end side is 90% or more and 100% or less of the width of the crown land portion. The width of the middle land portion on the first reference end side is 90% or more and 100% or less of the width of the crown land portion. The width of the middle land portion on the second reference end side is 97% or more and 107% or less of the width of the crown land portion. The width of the shoulder land portion on the second reference end side is 114% or more and 124% or less of the width of the crown land portion. The tire according to claim 4.

6. Of the crown land portion, the side on the first reference end side with respect to the equatorial plane is the first part, and the side on the second reference end side is the second part. The ratio of the width of the second part to the width of the crown land portion is 51% or more and 55% or less. The tire according to claim 5.

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