Motorcycle tires

Abstract

To provide a tire for automated two-wheeled vehicle that is less likely to cause peeling and cracking regardless of a dry or wet condition.SOLUTION: A tire for automated two-wheeled vehicle is provided, comprising a crown part located in a center in a tire axial direction and a pair of shoulder parts located outside the crown part, wherein a tanδ at 70°C of a rubber composition of the crown part (70°CtanδCr) is larger than a tanδ at 70°C of a rubber composition of the shoulder part (70°CtanδSh), wherein a tanδ at 0°C of the rubber composition of the crown part (0°CtanδCr) is smaller than a tanδ at 0°C of the rubber composition of the shoulder part (0°CtanδSh), wherein a tread surface of the tread part comprises a groove, and wherein the groove straddles over a boundary between the crown and shoulder parts and does not straddle over an equator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to motorcycle tires. [Background technology]

[0002] In motorcycle tires, the tread rubber primarily contacts the road surface at the center (crown) during straight-line driving, and primarily at the shoulder during cornering. Therefore, different performance characteristics are required for each section. For this reason, the properties of the rubber composition constituting the center and shoulder sections of motorcycle tire treads are often varied. (Patent Document 1) [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-127184 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, changing the properties of the rubber composition between the center and shoulder sections presents a problem: stress concentrates at their interface, making delamination more likely. In this case, providing a groove spanning the center and shoulder sections can be expected to suppress delamination under dry conditions by preventing stress concentration at the interface. However, under wet conditions, the groove can conversely become a starting point for fracture, making cracking more likely.

[0005] This disclosure aims to provide motorcycle tires that are less prone to delamination and cracking, regardless of whether they are dry or wet. [Means for solving the problem]

[0006] As a result of diligent research, the inventors have found that the above problems can be solved by adjusting the tread of a motorcycle tire having a crown portion and a pair of shoulder portions so that the 70°C tanδ is greater in the crown portion than in the shoulder portion and the 0°C tanδ is smaller in the crown portion than in the shoulder portion, and by providing a groove on the tread surface that straddles the boundary between the crown portion and the shoulder portion but does not straddle the equator. Further research has led to the completion of this disclosure.

[0007] In other words, this disclosure is, A motorcycle tire comprising a tread portion having a crown portion located in the center in the tire axial direction and a pair of shoulder portions located outside the crown portion, The tanδ(70°C tanδ) of the rubber composition constituting the crown portion Cr ) is the tanδ(70℃tanδ) of the rubber composition constituting the shoulder portion at 70℃. Sh Larger than ) The tanδ(0°C tanδ) of the rubber composition constituting the crown portion at 0°C Cr ) is the tanδ(0℃tanδ) of the rubber composition constituting the shoulder portion at 0℃. Sh Smaller than ) The tread surface of the tread portion is provided with grooves, A motorcycle tire in which the groove straddles the boundary between the crown portion and the shoulder portion, but does not straddle the equator. Regarding. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide motorcycle tires that are less prone to peeling and cracking, regardless of whether the conditions are dry or wet. [Brief explanation of the drawing]

[0009] [Figure 1] This is an example of a planar cross-sectional view of a motorcycle tire, including the tire's rotation axis. [Figure 2]This is an example of a cross-sectional view of a motorcycle tire in a plane including the tire's axis of rotation, showing the tire in contact with the road surface (when the crown portion is within the contact surface). [Figure 3] This is an example of a cross-sectional view in a plane including the tire's axis of rotation, showing the state of a motorcycle tire in contact with the road surface (when the crown extends beyond the contact surface). [Figure 4] This is an example of a diagram showing the tread area of ​​a motorcycle tire. [Figure 5] This is an example of a diagram showing the tread area of ​​a motorcycle tire. [Figure 6] This is a cross-sectional view of the motorcycle tire shown in Figure 1, which has the tread pattern shown in Figure 4, when cut along the cutting line Y in Figure 4, which passes through the tire's center of gravity. [Modes for carrying out the invention]

[0010] This disclosure relates to a motorcycle tire comprising a tread portion having a crown portion located in the center in the axial direction of the tire and a pair of shoulder portions located outside the crown portion, wherein the rubber composition constituting the crown portion has tanδ(70°C tanδ Cr ) is the tanδ(70℃tanδ) of the rubber composition constituting the shoulder portion at 70℃. Sh ) is greater than the tanδ(0℃tanδ) of the rubber composition constituting the crown portion at 0℃. Cr ) is the tanδ(0℃tanδ) of the rubber composition constituting the shoulder portion at 0℃. Sh The present invention relates to a motorcycle tire that is smaller than ) and has grooves on the tread surface of the tread portion, the grooves straddling the boundary between the crown portion and the shoulder portion, and not straddling the equator.

[0011] While not intended to be theoretically bound, the following mechanisms may be considered in this disclosure to reduce the likelihood of delamination and cracking, regardless of whether the conditions are dry or wet.

[0012] In other words, when a motorcycle is driven in a straight line under dry conditions, the temperature of the crown portion of the tread tends to be higher than that of the shoulder portion due to friction from contact with the ground. Furthermore, if the 70°C tanδ of the crown portion is higher than that of the shoulder portion, the heat generation increases, and the temperature of the crown portion becomes even higher. This creates a situation where the crown portion tends to be softer than the shoulder portion. In a motorcycle, frictional force acts from the crown portion to the shoulder portion when turning, but if the crown portion is softer than the shoulder portion in this way, the crown side interface tends to conform more easily to the shoulder side interface, so it is thought that delamination between the crown and shoulder will be less likely to occur. In addition, by providing the groove, stress is generated not only at the interface but also in the groove portion, so it is thought that stress concentration at the interface can be prevented and interfacial delamination can be further prevented.

[0013] While softening not only the crown but also the shoulder portion can provide a certain degree of delamination prevention, this reduces the overall rigidity of the tread, making it difficult to maintain stability during turns. Similarly, softening only the crown portion, regardless of temperature, can also provide a certain degree of delamination prevention, but this makes it difficult to maintain straight-line stability. In contrast, this disclosure provides an effect that prevents interfacial delamination while maintaining stability during turns and straight-line driving under dry conditions.

[0014] On the other hand, in wet conditions, friction with the road surface is reduced compared to dry conditions, so even if the crown and shoulder portions have similar hardness, interfacial delamination is less likely to occur. However, the presence of the grooves raises concerns that they may become the starting point for failure. Therefore, by increasing the 0°C tanδ of the shoulder portion compared to the crown portion to enhance heat generation, the temperature of the shoulder portion is made to be similar to that of the crown portion, which has more contact opportunities, thus reducing the temperature difference between the interfaces. This makes it easier for input from the road surface to be transmitted to the crown portion without delay during cornering, thus suppressing failure of the crown portion. Furthermore, since the grooves do not reach the equator, there is no portion that is sandwiched by the grooves in the circumferential direction above the equator, so failure is thought to be further suppressed. In particular, failure is thought to be suppressed even when a symmetrical pattern is used.

[0015] Among the said grooves, the groove depth D (mm) of the groove with the maximum groove depth preferably satisfies the following formula (1). Formula (1): D × 70°C tan δ Cr > 1.20

[0016] 70°C tan δ Cr When it becomes small, there is a tendency to increase the effect of preventing stress concentration due to the groove on the dry road surface. Therefore, when 70°C tan δ Cr becomes small, it is preferable to increase the groove depth.

[0017] Among the said grooves, the groove width W (mm) of the groove with the maximum groove width preferably satisfies the following formula (2). Formula (2): W × 70°C tan δ Cr > 0.80

[0018] 70°C tan δ Cr When it becomes small, there is a tendency to increase the effect of preventing stress concentration due to the groove on the dry road surface. Therefore, when 70°C tan δ Cr becomes small, it is preferable to widen the groove width.

[0019] Among the said grooves, the circumferential length component L C (mm) of the groove with the maximum circumferential length component preferably satisfies the following formula (3). Formula (3): L) C × (70°C tan δ Cr - 70°C tan δ Sh )> 0.05

[0020] 70°C tan δ Cr and 70°C tan δ Sh When the difference between and becomes small, there is a tendency to increase the effect of preventing stress concentration due to the groove on the dry road surface. Therefore, when the difference between 70°C tan δ Cr and 70°C tan δ Sh becomes small, it is preferable to increase the circumferential length component of the groove.

[0021] Of the grooves mentioned above, the groove with the smallest groove bottom thickness, H (mm), preferably satisfies the following formula (4). Equation (4): H / 0℃tanδ Cr >1.3

[0022] 0℃ tanδ Cr When the tanδ becomes large, it tends to become difficult to prevent temperature differences between interfaces on wet road surfaces, but if the groove bottom thickness (the thickness of the rubber in the tread at the bottom of the groove) is thick, it can move flexibly and relieve stress, making it less likely to break. Cr If the size increases, it is preferable to increase the thickness of the groove bottom.

[0023] Of the grooves mentioned above, the groove with the largest cross-sectional area S(mm²) 2 ) preferably satisfies the following formula (5). Equation (5):S / (0℃tanδ Sh -0℃ tanδ Cr )<150

[0024] 0℃ tanδ Sh and 0℃ tanδ Cr When the difference between the two becomes small, it tends to become difficult to create a temperature difference between the interfaces on a wet road surface, but a smaller groove cross-sectional area results in higher rigidity and makes it less prone to failure. Therefore, 0℃tanδ Sh and 0℃ tanδ Cr When the difference between the two becomes small, a smaller groove cross-sectional area is preferable.

[0025] The tanδ peak temperature (T) of the rubber composition constituting the crown portion Cr ) is the tanδ peak temperature (T) of the rubber composition constituting the shoulder portion. Sh A value lower than ) is preferable. This is because it allows for easier elastic deformation when in contact with the road surface, making it easier for the rubber to bite into the road surface, and thus improving wet grip performance.

[0026] The hardness of the rubber composition constituting the crown portion is preferably greater than that of the rubber composition constituting the shoulder portion. This is because it is expected to improve grip on the shoulder portion during turning.

[0027] The stress of the rubber composition constituting the crown portion at 300% elongation (M300) Cr ) is the stress (M300) of the rubber composition constituting the shoulder portion when stretched to 300%. Sh It is preferable that it be larger than ). This is because it is expected to achieve both high-speed durability during straight-line driving and grip during high-speed cornering.

[0028] <Definition> In this specification, unless otherwise specified, the dimensions of each part of a tire shall be the values ​​specified in the unloaded, standard condition when the tire is mounted on a standard rim and filled with the standard internal pressure.

[0029] A "standard rim" refers to the rim specified for each tire within the standard system that includes the standard on which the tire is based. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." In the case of tires not specified in the standard, it refers to the rim with the smallest diameter and narrowest rim width among rims that can be mounted on and can maintain internal pressure, i.e., rims that do not cause air leakage from between the rim and tire.

[0030] "Regular internal pressure" refers to the air pressure specified for each tire by each standard within the tire standard system, including the standard on which the tire is based. For example, it is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO.

[0031] "Regular load" refers to the load specified in the standards system, including the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are all considered regular loads.

[0032] "Groove depth D" is the groove depth (mm) of the groove with the maximum depth among the grooves on the tread surface. The groove depth represents the maximum depth within that groove. For example, groove depth D is shown in Figure 6.

[0033] "Groove width W" is the groove width (mm) on the tread surface of the groove with the largest groove width on the tread surface. The groove width refers to the maximum groove width in the direction perpendicular to the longitudinal direction of the groove. The groove width W is as shown in Figures 4 and 5, for example.

[0034] "Length component L in the circumferential direction of the groove" C " is the circumferential length component (mm) of the groove with the longest circumferential length component among the grooves on the tread surface. Circumferential length component L C This is shown, for example, in Figures 4 and 5.

[0035] "Groove bottom thickness H" refers to the thickness (mm) of the tread rubber at the bottom of the groove with the minimum groove bottom thickness among the grooves on the tread surface. The groove bottom thickness represents the minimum value of the groove bottom thickness in that particular groove. The groove bottom thickness H is, for example, as shown in Figure 6.

[0036] "Groove cross-sectional area S" is the groove cross-sectional area (mm²) of the groove with the largest cross-sectional area among the grooves provided in the tread. 2 The groove cross-sectional area refers to the cross-sectional area of ​​the groove in a cross-sectional view obtained by cutting the groove with a plane passing through the tire's center of gravity in a direction perpendicular to the longitudinal direction of the groove. The groove cross-sectional area S is, for example, as shown in Figure 6.

[0037] The "crown portion" is the part of the tread located in the center of the tread, extending outward in the axial direction of the tire beyond ±5% of the tread width from the tire equator, but not reaching the tread edge. However, this excludes the portion of the tread that is equipped with an electrically conductive rubber component.

[0038] The "shoulder section" is the part of the tread that is located on the outer side of the crown section in the axial direction of the tire and extends to the edge of the tread.

[0039] "Tread width" is the distance from one tread edge to the other tread edge, which is the outermost edge in the axial direction of the tire, on the tread surface, which is the part of the tread that comes into contact with the road surface.

[0040] "Electrically conductive rubber components" are embedded in the tread of the tire, with a portion exposed to the tire's contact surface, in order to effectively discharge static electricity generated during tire operation. This includes components referred to as base pens.

[0041] <Measurement method> The "tanδ peak temperature of the rubber composition" is determined by measuring the tanδ temperature distribution curve using a GABO iplexer series under the conditions of a frequency of 10 Hz, initial strain of 10%, dynamic strain of ±0.5%, and heating rate of 2°C / min. The temperature corresponding to the largest tanδ value in the obtained temperature distribution curve (tanδ peak temperature) is then determined. The sample used for measurement is a vulcanized rubber composition measuring 20 mm in length, 4 mm in width, and 1 mm in thickness. When prepared by cutting from the tread of a tire, the length direction is the circumferential direction of the tire.

[0042] "0℃tanδ" is the loss tangent measured using a GABO Iplexer series instrument under the conditions of 0℃ temperature, 10Hz frequency, 10% initial strain, 2.5% dynamic strain, and extension mode. The sample used for loss tangent measurement is a vulcanized rubber composition measuring 20mm in length, 4mm in width, and 1mm in thickness. When prepared by cutting from the tire tread, the length direction is the circumferential direction of the tire.

[0043] "70°C tanδ" is the loss loss tangent measured using a GABO iplexer series instrument under the conditions of 70°C temperature, 10Hz frequency, 10% initial strain, 1% dynamic strain, and extension mode. Samples for loss loss tangent measurement are prepared in the same manner as for 0°C tanδ.

[0044] For "M300," a 1mm thick, No. 7 dumbbell-shaped test piece is prepared by cutting it from the inside of the rubber layer of the tread of each test tire so that the circumferential direction of the tire is the tensile direction. A tensile test is then performed in accordance with JIS K 6251 "Vulcanized rubber and thermoplastic rubber - Method for determining tensile test properties" at a 23°C atmosphere and a tensile speed of 3.3 mm / second to determine the stress at 300% elongation (M300) (MPa).

[0045] To determine the hardness of a rubber composition, a sample is prepared by cutting out a section of the tread from the tread portion that forms the contact surface of a test tire, such that the tire radius is the thickness direction. A Type A durometer is then pressed against the sample from the contact surface side at 23°C in accordance with JIS K 6253 to measure the hardness.

[0046] "Styrene content" is, 1 It is calculated by 1H-NMR measurement. For example, it is applied to styrene-containing rubbers such as SBR.

[0047] The "vinyl bond content (amount of 1,2-bonded butadiene units)" is measured by infrared absorption spectroscopy. This method is applied, for example, to SBR, BR, etc.

[0048] The "glass transition temperature of rubber components" is a value measured in accordance with JIS K 7121 using a differential scanning calorimeter (Q200) manufactured by T.A. Instruments Japan Co., Ltd., under conditions of a heating rate of 10°C / min. For example, it applies to SBR, BR, etc.

[0049] "Cis-1,4-bond content (cis content)" is a value calculated by infrared absorption spectroscopy. For example, it is applied to BR (Brazilian Glutamate).

[0050] The "weight-average molecular weight" can be determined by converting the measured value using gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation) to standard polystyrene equivalent. For example, it is applicable to SBR, BR, resins, liquid polymers, etc.

[0051] The "N2SA of carbon black" is measured in accordance with JIS K 6217-2 "Basic properties of carbon black for rubber - Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method".

[0052] The DBP of carbon black is measured in accordance with JIS K 6217-4:2001.

[0053] The N2SA content of silica is measured by the BET method in accordance with ASTM D3037-93.

[0054] The "softening point" is the temperature at which the sphere drops when the softening point, as defined in JIS K 6220-1:2001, is measured using a ring-type softening point measuring device. It is applied, for example, to resins.

[0055] The "SP value" refers to the solubility parameter calculated using the Hoy method based on the compound's structure. The Hoy method is a calculation method described in KLHoy's "Table of Solubility Parameters," Solvent and Coatings Materials Research and Development Department, Union Carbites Corp. (1985). The SP value is applied to materials such as resins.

[0056] <Tires for motorcycles> The motorcycle tires described in this disclosure are explained below.

[0057] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings as appropriate. Figure 1 is an example of a plan view of a motorcycle tire including the tire rotation axis (also called the "tire axis") (however, the grooves provided on the tread surface are omitted from the display. The same applies to Figures 2 and 3). The motorcycle tire 1 comprises a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 arranged on the radially outer side of the carcass 6 and inside the tread portion 2. In the above cross-section, the tread surface 2A of the tread portion 2 that contacts the road surface is convex and curves in an arc outward in the radial direction of the tire. The outer end of the tread surface 2A in the tire axial direction is the tread edge 2e.

[0058] [Tread area] The aforementioned motorcycle tire comprises a tread portion comprising a crown portion located in the center in the axial direction of the tire and a pair of shoulder portions located outside the crown portion. Furthermore, the pair of shoulder portions may each be further divided. Also, the crown portion may be further divided.

[0059] In this disclosure, the crown portion and the shoulder portion satisfy a predetermined relationship, but if at least one of the crown portion and the shoulder portion is divided, then at least one pair of adjacent portions in the region axially outward from the tread width ±5% of the tire equator satisfy the predetermined relationship that the crown portion and the shoulder portion of this disclosure must satisfy.

[0060] In other words, in the region axially outward from the position +5% of the tread width with respect to the tire equator, at least one pair of adjacent portions satisfies a predetermined relationship that the crown portion and shoulder portion of the present disclosure must satisfy, and on the opposite side, in the region axially outward from the position -5% of the tread width with respect to the tire equator, at least one pair of adjacent portions satisfies a predetermined relationship that the crown portion and shoulder portion of the present disclosure must satisfy. In this case, the portion of these two adjacent portions axially inward is the crown portion of the present disclosure, and the portion axially outward is the shoulder portion of the present disclosure.

[0061] In this disclosure, if at least one of the crown portion and the shoulder portion is divided, it is preferable that all of the crown portion and all of the shoulder portion satisfy a predetermined relationship that the crown portion and the shoulder portion of this disclosure must satisfy.

[0062] In the tread portion 2, tread rubber 9 is arranged radially outward from the belt layer 7. In this embodiment, the tread rubber 9 constitutes the area from the outer surface of the belt layer 7 to the tread surface 2A. The tread rubber 9 consists of a crown portion 9A centered on the tire equator C, and a pair of shoulder portions 9B adjacent to the crown portion 9A and extending to the tread edge 2e. That is, two types of members, the crown portion 9A and the shoulder portions 9B, are arranged side by side from near the tire equator C toward both sides in the tire axial direction. In Figure 1, the crown portion 9A and the shoulder portions 9B are separated by a normal line 12 drawn on the tread surface 2A, but the manner of separation is not limited; for example, they may be separated by a boundary line that slopes outward or inward in the tire axial direction from the tread surface 2A toward the belt layer 7.

[0063] The dividing point (boundary line) between the crown portion 9A and the shoulder portion 9B may be inside the width X of the contact surface (the portion where the tread rubber 9 contacts the road surface 100 when filled with the normal internal pressure and subjected to the normal load), as shown in Figure 2, or it may be outside (see Figure 3). The state shown in Figure 2 is called the "inside the contact surface" state, and the state shown in Figure 3 is called the "outside the contact surface" state. From the viewpoint of preventing step wear caused by differences in the wear resistance of the tread compound, it is preferable that the dividing point be outside the width X.

[0064] [Rubber composition that makes up the tread] (70℃ tanδ) In this disclosure, the tanδ(70°C tanδ) of the rubber composition constituting the crown portion is given. Cr ) is the tanδ at 70°C of the rubber composition constituting the shoulder portion (70°C tanδ Sh ) is greater than. In this disclosure, 70°C tanδ is an index relating to the heat generation of the rubber composition when driving on a dry road surface. 70°C tanδ Cr 70℃ tanδ ShBecause it is larger, the crown portion, which receives a large amount of friction from the road surface during straight-line driving, is more prone to temperature increases due to heat generation, and as a result, the crown portion tends to become softer than the shoulder. In this disclosure, 70℃tanδ Cr and 70℃ tanδ Sh The difference between these two values ​​is preferably 0.01 or greater, more preferably 0.02 or greater, and even more preferably 0.03 or greater. On the other hand, there is no particular upper limit specified for this difference, but it is usually 0.10 or less, or 0.09 or less, or 0.08 or less, or 0.07 or less.

[0065] 70℃ tanδ Cr The value is preferably 0.19 or higher, more preferably 0.20 or higher, even more preferably 0.21 or higher, even more preferably 0.22 or higher, even more preferably 0.23 or higher, even more preferably 0.24 or higher, and even more preferably 0.25 or higher. This makes it easier to obtain the effects of the present disclosure. On the other hand, 70℃ tanδ Sh The value is preferably 0.22 or less, more preferably 0.21 or less, even more preferably 0.20 or less, even more preferably 0.19 or less, and even more preferably 0.18 or less. This makes it easier to obtain the effects of the present disclosure.

[0066] The 70°C tanδ can be adjusted by the type and amount of components blended into the rubber composition. For example, it tends to increase when the amount of fillers (carbon black, silica, etc.) or oil is increased, and decreases when the amount of fillers (carbon black, silica, etc.) or oil is decreased. The 70°C tanδ is measured by the method described above.

[0067] (0℃ tanδ) In this disclosure, the tanδ(0℃tanδ) of the rubber composition constituting the crown portion at 0℃ Cr ) is the tanδ at 0°C of the rubber composition constituting the shoulder portion (0°C tanδ Sh) is smaller than. In this disclosure, 0°C tanδ is an index relating to the heat generation of the rubber composition when driving on a wet road surface. 0°C tanδ Cr 0℃ tanδ Sh Being smaller than the crown portion increases the heat generation of the shoulder portion, and the temperature of the shoulder portion becomes similar to that of the crown portion, which has more contact opportunities, making it less likely for a temperature difference to occur between the interfaces. In this disclosure, 0℃tanδ Sh and 0℃ tanδ Cr The difference between these two values ​​is preferably 0.10 or greater, more preferably 0.18 or greater, and even more preferably 0.20 or greater. On the other hand, there is no particular upper limit specified for this difference, but it is usually 0.50 or less, or 0.40 or less, or 0.38 or less, or 0.37 or less.

[0068] 0℃ tanδ Cr The value is preferably 0.88 or less, more preferably 0.80 or less, even more preferably 0.70 or less, even more preferably 0.65 or less, even more preferably 0.60 or less, and even more preferably 0.58 or less. This makes it easier to obtain the effects of the present disclosure. On the other hand, 0℃tanδ Sh Preferably, the value is 0.75 or higher, more preferably 0.78 or higher, even more preferably 0.80 or higher, and even more preferably 0.81 or higher. This makes it easier to obtain the effects of the present disclosure.

[0069] The 0°C tanδ can be adjusted by the type and amount of components blended into the rubber composition. For example, it tends to increase when the amount of fillers (carbon black, silica, etc.) or oil is increased, and decreases when the amount of fillers (carbon black, silica, etc.) or oil is decreased. The 0°C tanδ is measured by the method described above.

[0070] (tanδ peak temperature) In this disclosure, the tanδ peak temperature (T) of the rubber composition constituting the crown portion is specified. Cr ) is determined from the viewpoint of wet grip performance by the tanδ peak temperature (T) of the rubber composition constituting the shoulder portion.Sh It is preferable that it be lower than ). Sh and T Cr The difference between the two temperatures is preferably 1°C or more. On the other hand, the difference is preferably 10°C or less, and preferably 7°C or less.

[0071] T Cr The temperature is preferably -20°C or higher, more preferably -15°C or higher, and even more preferably -12°C or higher. On the other hand, T Cr The temperature is preferably 5°C or lower, more preferably 0°C or lower. Sh The temperature is preferably -15°C or higher, more preferably -10°C or higher, and even more preferably -5°C or higher. On the other hand, T Sh The temperature is preferably 10°C or lower, more preferably 5°C or lower, and even more preferably 3°C or lower.

[0072] The tanδ peak temperature of a rubber composition can be adjusted by the type and amount of components blended into the rubber composition. For example, it tends to increase when the amount of filler is increased or the amount of softener is decreased, and decreases when the amount of filler is decreased or the amount of softener is increased. The tanδ peak temperature is measured by the method described above.

[0073] (hardness) In this disclosure, the hardness of the rubber composition constituting the crown portion is preferably greater than the hardness of the rubber composition constituting the shoulder portion, from the viewpoint of grip performance during turning. The difference between the hardness of the rubber composition constituting the crown portion and the hardness of the rubber composition constituting the shoulder portion is preferably 3 or more, and preferably 5 or more. There is no particular upper limit to this difference, but it is usually 10 or less.

[0074] The hardness of a rubber composition can be adjusted by the type and amount of components blended into the rubber composition. For example, increasing the amount of softener tends to decrease the hardness, decreasing the amount of softener tends to increase the hardness, increasing the amount of filler tends to increase the hardness, decreasing the amount of filler tends to decrease the hardness, decreasing the amount of sulfur or vulcanization accelerator tends to decrease the hardness, and increasing the amount of sulfur or vulcanization accelerator tends to increase the hardness. The hardness is measured by the method described above.

[0075] (M300) In this disclosure, the stress of the rubber composition constituting the crown portion at 300% elongation (M300) Cr ) is determined from the viewpoint of achieving both high-speed durability during straight-line driving and grip during high-speed turns, by considering the stress of the rubber composition constituting the shoulder portion at 300% elongation (M300 Sh It is preferable that it be larger than ). M300 Cr M300 Sh It is preferable that the ratio be 110% or more, and more preferably 120% or more. M300 Cr M300 Sh It is 150% or less, or 140% or less, or 130% or less.

[0076] The M300 of a rubber composition can be adjusted by the type and amount of components blended into the rubber composition. It tends to increase when the amount of filler is increased or the amount of softener is decreased, and tends to decrease when the amount of filler is decreased or the amount of softener is increased. M300 is measured by the method described above.

[0077] [Grooves on the tread surface] The tread surface of the tread portion is provided with grooves. These grooves straddle the boundary between the crown portion and the shoulder portion, but do not straddle the equator. If the shoulder portion is further divided, it is preferable that the grooves also straddle the boundary of the divided portion.

[0078] The groove in this disclosure straddles the boundary between the crown and shoulder portions. Because of this groove, stress is generated not only at the interface but also in the groove portion of the tread in this disclosure, thus preventing stress concentration at the interface and further preventing interfacial delamination. Here, "the groove straddles the boundary" simply means that the groove must straddle the boundary and is not limited further; however, since the groove is intended to prevent stress concentration at the interface, it is desirable that it not only straddles the boundary but also extends to both sides of the boundary. This is desirable from the viewpoint of preventing interfacial delamination because stress can be generated in areas other than the boundary.

[0079] The grooves in this disclosure do not straddle the equator. By not straddling the equator, there is no portion of the tire that is sandwiched by the grooves in the circumferential direction above the equator. Therefore, even with grooves in place, the circumferential rigidity near the tire equator can be increased, which in turn can improve high-speed stability.

[0080] Figure 4 is an example of an exploded view of the tread portion of a motorcycle tire according to the present disclosure. In Figure 4, grooves are provided that straddle the boundary between the crown portion and the shoulder portion of the tread portion, but do not straddle the equator. Here, R in the figure represents the direction of tire rotation. In Figure 4, the grooves consist of longer main grooves and shorter secondary grooves. The main grooves and secondary grooves are also provided alternately in the circumferential direction of the tire and are arranged in a symmetrical pattern with respect to the tire equator. Figure 5 is another example of an exploded view of the tread portion of a motorcycle tire according to the present disclosure. In Figure 5, grooves are provided that straddle the boundary between the crown portion and the shoulder portion of the tread portion, but do not straddle the equator. Here, R in the figure represents the direction of tire rotation. In Figure 5, the grooves consist of longer main grooves and shorter secondary grooves. The main grooves and secondary grooves are also provided alternately in the circumferential direction of the tire and are arranged in a symmetrical pattern with respect to the tire equator.

[0081] In this disclosure, the groove area ratio (the ratio of the groove area to the total area of ​​the tread) is not particularly limited as long as it is a ratio commonly used in this art, but for example, it is preferably 5% or more, more preferably 10% or more, even more preferably 15% or more, and also preferably 40% or less, more preferably 35% or less, and even more preferably 30% or less.

[0082] The following are the groove depth D, groove width W, and circumferential length component L of the groove. C Next, we will explain the groove bottom thickness H and groove cross-sectional area S. These are also shown in Figures 4, 5, and 6. Figure 6 is a cross-sectional view of the motorcycle tire shown in Figure 1, which has the tread pattern shown in Figure 4, when cut along the cutting line Y on Figure 4 that passes through the tire's center of gravity.

[0083] (Groove depth D) Formula (1): D×70℃tanδ Cr >1.20 In this equation, the value of the right-hand side is preferably 1.30, more preferably 1.40, and even more preferably 1.50. D × 70°C tanδ Cr The upper limit of the value is not particularly limited, but is usually less than 3.00, preferably less than 2.50, and more preferably less than 2.00.

[0084] The groove depth D is preferably 4.0 mm or more, more preferably 4.5 mm or more, and even more preferably 4.8 mm or more. On the other hand, the groove depth D is preferably 6.5 mm or less, and more preferably 6.0 mm or less.

[0085] (Groove width W) Formula (2): W×70℃tanδ Cr >0.80 In this equation, the value of the right-hand side is preferably 0.90, more preferably 1.00, and even more preferably 1.10. W × 70℃ tanδ Cr The upper limit of the value is not particularly limited, but is usually less than 2.50, preferably less than 2.00, and more preferably less than 1.50.

[0086] The groove width W is preferably 3.0 mm or more, more preferably 3.3 mm or more, and even more preferably 3.5 mm or more. On the other hand, the groove width W is preferably 6.0 mm or less, more preferably 5.5 mm or less, and even more preferably 5.0 mm or less.

[0087] (Circumferential length component of the groove L) C ) Formula (3):L C ×(70℃ tanδ Cr -70℃ tanδ Sh )>0.05 In this case, the value of the right-hand side is preferably 0.06, more preferably 0.07, and even more preferably 0.08. C ×(70℃ tanδ Cr -70℃ tanδ Sh The upper limit of the value of ) is not particularly limited, but is usually less than 4.00, preferably less than 3.50, and more preferably 3.00 or less.

[0088] Circumferential length component L C The circumferential length component L is preferably 30.0 mm or more, and more preferably 35.0 mm or more. C The length is preferably 50.0 mm or less, more preferably 45.0 mm or less, and even more preferably 40.0 mm or less.

[0089] (Trench bottom thickness H) Equation (4): H / 0℃tanδ Cr >1.3 In this equation, the value of the right-hand side is preferably 1.4, more preferably 1.5, and even more preferably 1.6. H / 0℃tanδ Cr The upper limit of the value is not particularly limited, but is usually less than 6.0, preferably less than 5.0, and more preferably less than 4.0.

[0090] The groove bottom thickness H is preferably 1.5 mm or more, and more preferably 2.0 mm or more. On the other hand, the groove bottom thickness H is preferably 3.0 mm or less, and more preferably 2.5 mm or less.

[0091] (Groove cross-sectional area S) Formula (5): S / (0 °C tan δ Sh - 0 °C tan δ Cr ) < 150 In this case, the value on the right side is preferably 140, more preferably 130, and even more preferably 120. S / (0 °C tan δ Sh - 0 °C tan δ Cr ) The lower limit of the value is not particularly limited, but is usually less than 200, preferably less than 180, and more preferably less than 160.

[0092] The groove cross-sectional area S is preferably 14.0 mm 2 or more, more preferably 15.0 mm 2 or more, and even more preferably 16.0 mm 2 or more. On the other hand, the groove cross-sectional area S is preferably 35.0 mm 2 or less, more preferably 29.0 mm 2 or less, and even more preferably 26.0 mm 2 or less.

[0093] <Components constituting the rubber composition> The components constituting the rubber composition according to the present disclosure will be described below. Here, the rubber composition according to the present disclosure includes both the rubber composition constituting the crown portion of the tread portion and the rubber composition constituting the shoulder portion of the tread portion.

[0094] [Rubber component] In the present disclosure, the rubber component preferably includes a diene rubber. In a preferred embodiment of the present disclosure, the rubber component preferably consists only of a diene rubber.

[0095] (Diene rubber) Examples of the diene rubber include styrene-butadiene rubber (SBR), butadiene rubber (BR), etc. The diene rubber preferably includes SBR and BR, and may consist only of SBR and BR.

[0096] ≪SBR≫ The type of SBR used is not particularly limited; for example, emulsion-polymerized SBR (E-SBR), solution-polymerized SBR (S-SBR), and other types commonly used in the tire industry can be used. One or more types of SBR can be used.

[0097] Furthermore, as SBR, either unmodified SBR or modified SBR can be used. Modified SBR can be any of the types commonly used in the tire industry, including those with functional groups that interact with fillers such as silica. Examples of such SBRs include terminally modified SBRs in which at least one end of the SBR is modified with a compound (modifier) ​​having the following functional group; main-chain modified SBRs in which the main chain has the following functional group; main-chain terminally modified SBRs in which the main chain and terminals have the following functional groups (for example, a main-chain terminally modified SBR in which the main chain has the following functional group and at least one end is modified with a compound (modifier) ​​having the following functional group); and terminally modified SBRs that are modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and in which hydroxyl groups or epoxy groups are introduced.

[0098] Examples of the above-mentioned functional groups include amino groups (preferably amino groups in which the hydrogen atoms of the amino group are substituted with C1-C6 alkyl groups), amide groups, silyl groups, alkoxysilyl groups (preferably C1-C6 alkoxysilyl groups), isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups (preferably C1-C6 alkoxy groups), hydroxyl groups, oxy groups, epoxy groups, and the like. These functional groups may also have substituents. Examples of substituents include those into which functional groups such as amino groups, amide groups, alkoxysilyl groups, carboxyl groups, and hydroxyl groups have been introduced.

[0099] Furthermore, modified SBRs include those obtained by further hydrogenating, epoxidizing, or tin-modifying the above-mentioned unmodified or modified SBRs. Among these, SBR obtained by further hydrogenating the above-mentioned modified SBR (modified hydrogenated SBR) is preferred. Hydrogenated SBR is preferable from the viewpoint of the effects of this disclosure because it improves the mobility of the molecular chain by reducing the number of double bonds and increasing the number of single bonds, thereby improving the entanglement effect between polymers and tending to increase reinforcing properties.

[0100] For SBR, either oil-expanded SBR or non-oil-expanded SBR can be used. When using oil-expanded SBR, the amount of oil expanded in the SBR, that is, the amount of oil-expanding oil contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of rubber solids in the SBR.

[0101] For example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Co., Ltd. can be used.

[0102] The styrene content of SBR is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, for the reasons that the effects of this disclosure are more favorably obtained. Furthermore, the styrene content is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. The styrene content is calculated by the measurement method described above.

[0103] The amount of vinyl bonded to SBR is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, for the reasons that the effects of this disclosure are more favorably obtained. Furthermore, the amount of vinyl bonded is preferably 80 mol% or less, more preferably 70 mol% or less, even more preferably 60 mol% or less, and even more preferably 50 mol% or less. The amount of vinyl bonded (amount of 1,2-bonded butadiene units) is measured by the method described above.

[0104] The glass transition temperature (Tg) of SBR is preferably -90°C or higher, more preferably -50°C or higher, and even more preferably -40°C or higher, for the reason that the effects of this disclosure are more favorably obtained. Furthermore, the Tg is preferably 0°C or lower, more preferably -10°C or lower, even more preferably -15°C or lower, even more preferably -20°C or lower, and even more preferably -25°C or lower. The glass transition temperature is measured by the method described above.

[0105] The weight-average molecular weight (Mw) of SBR is preferably 200,000 or more, and more preferably 300,000 or more, for the reasons that the effects of this disclosure are more favorably obtained. Furthermore, the Mw is preferably 2,000,000 or less, more preferably 1,500,000 or less, and more preferably 1,000,000 or less. The weight-average molecular weight (Mw) can be determined by the method described above.

[0106] The SBR content in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. Alternatively, the SBR content may be 100% by mass. In the case of oil-extracted SBR, the SBR content refers to the amount of SBR itself, excluding the oil used for oil-extraction.

[0107] ≪BR≫ The type of BR used is not particularly limited. For example, BR with a cis-1,4 bond content (cis content) of 90% or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), and other types commonly used in the tire industry can be used. One or more types of BR can be used. Of these, high-cis BR is preferred.

[0108] Examples of high-cis BR include those manufactured by Nippon Zeon Co., Ltd., Ube Industries, Ltd., and JSR Corporation. The cis content of high-cis BR is preferably 95% or more, more preferably 96% or more, even more preferably 97% or more, and even more preferably 98% or more. Rare-earth BR is synthesized using a rare-earth element catalyst, and the vinyl bond content (amount of 1,2-linked butadiene units) is preferably 1.8 mol% or less, more preferably 1.0 mol% or less, and even more preferably 0.8% mol or less, and the cis content (cis-1,4 bond content) is preferably 95 mol% or more, more preferably 96% mol or more, and even more preferably 97% or more. Examples of rare-earth BR include those manufactured by Lanxess. The cis-1,4 bond content and vinyl bond content are measured by the method described above.

[0109] SPB-containing BR refers to a type in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR, but are chemically bonded to and dispersed in BR. Examples of such SPB-containing BR include those manufactured by Ube Industries, Ltd.

[0110] Modified BRs include those that have undergone the same modifications as described above for SBRs. Other examples of modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound (tin-modified BR), and butadiene rubber having a condensed alkoxysilane compound at its active end (silica-modified BR). Examples of such modified BRs include those manufactured by ZS Elastomer Co., Ltd.

[0111] The glass transition temperature (Tg) of BR is preferably -130°C or higher, more preferably -120°C or higher, and even more preferably -110°C or higher, for the reasons that the effects of this disclosure are more favorably obtained. Furthermore, the Tg is preferably 0°C or lower, more preferably -10°C or lower, even more preferably -60°C or lower, even more preferably -70°C or lower, and even more preferably -80°C or lower. In this specification, the glass transition temperature is measured by the method described above.

[0112] The weight-average molecular weight (Mw) of BR is preferably 200,000 or more, and more preferably 300,000 or more, for the reasons that the effects of this disclosure are more favorably obtained. Furthermore, the Mw is preferably 2,000,000 or less, more preferably 1,500,000 or less, and more preferably 1,000,000 or less. In this specification, the weight-average molecular weight (Mw) can be determined by the method described above.

[0113] The BR content in 100% by mass of the rubber component is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. There is no particular limit to the lower limit of the BR content; it may be 0% by mass, or for example, 5% by mass or more, 10% by mass or more, or 20% by mass or more.

[0114] <<Other Diene-based Rubbers>> The rubber component may contain other diene-based rubber components other than the aforementioned SBR and BR. Other diene-based rubber components can include crosslinkable rubber components commonly used in the rubber industry, such as natural rubber (NR), isoprene rubber (IR), styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and polynorbornene rubber. These other rubber components may be used individually or in combination of two or more.

[0115] (Rubber components other than diene-based rubbers) The rubber component can include non-diene rubber. Examples of non-diene rubber include butyl rubber (IIR), hydrogenated nitrile rubber (HNBR), ethylene propylene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. The non-diene rubber may be used alone or in combination of two or more kinds.

[0116] [Filler] As the filler, those generally used in the tire industry can be used, and in addition to silica and carbon black, aluminum hydroxide, alumina (aluminum oxide), clay, calcium carbonate, mica, etc. can be mentioned. One kind or two or more kinds of fillers can be used.

[0117] As fillers other than silica, those containing silica and carbon black and those consisting only of silica and carbon black can be preferably used.

[0118] (Silica) The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. Among them, hydrous silica prepared by a wet method is preferred because it has many silanol groups. The silica may be used alone or in combination of two or more kinds.

[0119] From the viewpoints of low fuel consumption performance and abrasion resistance performance, the nitrogen adsorption specific surface area (N2SA) of silica is preferably 140 m 2 / g or more, more preferably 160 m 2 / g or more, and even more preferably 170 m 2 / g or more. Also, from the viewpoints of low fuel consumption performance and processability, it is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, and even more preferably 250 m 2 / g or less. Note that the N2SA of silica is measured by the above method.

[0120] From the viewpoint of the effects of this disclosure, the silica content per 100 parts by mass of rubber component is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more. Furthermore, from the viewpoint of wear resistance performance, it is preferably 150 parts by mass or less, more preferably 130 parts by mass or less, even more preferably 110 parts by mass or less, and even more preferably 90 parts by mass or less.

[0121] (Carbon Black) As for carbon black, commonly used in the rubber industry can be used as appropriate, for example, GPF, FEF, HAF, ISAF, SAF, etc., or N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, etc. Commercially available products from companies such as Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Columbia Carbon Corporation can be used. These can be used individually or in combination of two or more types.

[0122] The nitrogen adsorption specific surface area (N2SA) of carbon black is 40m², considering factors such as abrasion resistance and grip performance. 2 Preferably 50m 2 More preferably 70m 2 More preferably 100m / g or more. 2 A concentration of 300m or more is even more preferable. Furthermore, from the viewpoint of good dispersion, the N2SA should be 300m 2 Preferably less than / g, 250m 2 Less than / g is more preferable, 200m 2 More preferably less than / g, 160m 2 A value of less than / g is even more preferable. The N2SA of carbon black is measured by the method described above.

[0123] From the viewpoint of sufficient reinforcing properties, the dibutyl phthalate (DBP) oil absorption of carbon black is preferably 50 ml / 100g or more, and more preferably 100 ml / 100g or more. Furthermore, from the viewpoint of wet grip performance, the DBP of carbon black is preferably 200 ml / 100g or less, and more preferably 150 ml / 100g or less. The DBP of carbon black is measured by the method described above.

[0124] From the viewpoint of good UV crack resistance and good abrasion resistance, the carbon black content is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of rubber component. Furthermore, from the viewpoint of processability and heat generation, the content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 120 parts by mass or less, even more preferably 110 parts by mass or less, and even more preferably 100 parts by mass or less.

[0125] The total content of the filler is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, per 100 parts by mass of the rubber component, from the viewpoint of sufficient reinforcement. On the other hand, from the viewpoint of wet grip performance, the content is preferably 250 parts by mass or less, more preferably 180 parts by mass or less, and even more preferably 150 parts by mass or less.

[0126] (Silane coupling agent) The rubber composition preferably uses a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent conventionally used in the rubber industry can be used. Specific examples of silane coupling agents include, for example, silane coupling agents having a sulfide group such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; silane coupling agents having a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and mercapto-based silane coupling agents from Momentive; and silane coupling agents having a thioester group such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane. Examples of silane coupling agents include: silane coupling agents having vinyl groups such as vinyltriethoxysilane and vinyltrimethoxysilane; silane coupling agents having amino groups such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, silane coupling agents having sulfide groups, silane coupling agents having mercapto groups, and silane coupling agents having thioester groups are preferred, with silane coupling agents having sulfide groups being more preferred. These silane coupling agents may be used individually or in combination of two or more.

[0127] From the viewpoint of sufficient chipping resistance, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of silica. Furthermore, from the viewpoint of the blending effect commensurate with the content, the content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less, per 100 parts by mass of silica.

[0128] [oil] The rubber composition may contain oil. The oil is not particularly limited, and for example, process oils, vegetable oils, and mixtures thereof can be used. Examples of process oils include paraffinic process oils, naphthenic process oils, and aromatic process oils. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, safflower oil, and tung oil. Of these, aromatic process oils are preferred. The oil may be used alone or in combination of two or more types.

[0129] From the viewpoint of the effects of this disclosure, the oil content is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of rubber component. From the viewpoint of handling stability, the content is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less. In this specification, the oil content also includes the amount of oil contained in the oil-spread rubber.

[0130] [Other compounding agents] In addition to the above-mentioned components, the rubber composition may appropriately contain compounding agents commonly used in the tire industry, such as resins, liquid polymers, waxes, processing aids, antioxidants, vulcanizing agents such as stearic acid, zinc oxide, inorganic potassium salts, and sulfur, as well as vulcanization accelerators.

[0131] (resin) The resin can be any resin component commonly used in the tire industry. Examples of such resin components include petroleum resins, terpene resins, rosin resins, phenolic resins, coumarone resins, etc., which may be used individually or in combination of two or more. Among these, petroleum resins are preferred from the viewpoint of the effects of this disclosure.

[0132] ≪Petroleum resin≫ The petroleum resin is not particularly limited, but examples include aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic copolymer petroleum resins. One type may be used alone, or two or more types may be used in combination. As an aliphatic petroleum resin, a resin obtained by cationic polymerization of unsaturated monomers such as isoprene and cyclopentadiene, which are petroleum fractions with 4 to 5 carbon atoms (C5 fraction), can be used (also called C5 petroleum resin). As an aromatic petroleum resin, a resin obtained by cationic polymerization of monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions with 8 to 10 carbon atoms (C9 fraction), can be used (also called C9 petroleum resin). As an aliphatic / aromatic copolymer petroleum resin, a resin obtained by copolymerizing the above C5 fraction and C9 fraction (also called C5C9 petroleum resin) is used. Hydrogenated petroleum resins may also be used. Among these, aromatic petroleum resins are preferably used. An example of an aromatic petroleum resin is α-methylstyrene resin. Examples of α-methylstyrene-based resins include α-methylstyrene homopolymers (poly-α-methylstyrene) and copolymers of α-methylstyrene with other compounds including aromatic compounds and phenolic compounds. Other compounds that can constitute these copolymers include styrene, methylstyrene, methoxystyrene, and divinylbenzene. α-methylstyrene-based resins manufactured by Arizona Chemical Corporation are preferably used.

[0133] Terpene resins Examples of terpene resins include polyterpene resins, terpene phenol resins, and terpene styrene resins. These may be used individually or in combination of two or more. Among these, terpene styrene resin is particularly suitable because it has good compatibility with both SBR and BR, and sulfur is easily dispersed within the rubber components.

[0134] Polyterpene resins are resins made from at least one terpene compound selected from α-pinene, β-pinene, limonene, dipentene, etc. Terpene resins may be used individually or in combination of two or more compounds.

[0135] Terpene phenol resins are resins made from the aforementioned terpene compounds and phenolic compounds. Terpene styrene resins are resins made from the aforementioned terpene compounds and styrene. Polyterpene resins and terpene styrene resins may be hydrogenated resins (hydrogenated polyterpene resins, hydrogenated terpene styrene resins). Hydrogenation of terpene resins can be carried out by known methods, and commercially available hydrogenated resins can also be used.

[0136] In this disclosure, commercially available terpene resins may be used. Examples of such commercially available products include those manufactured and sold by Yasuhara Chemical Co., Ltd., etc.

[0137] ≪Rosin-based resin≫ The rosin-based resin is not particularly limited, but examples include natural resin rosin, and rosin-modified resins obtained by hydrogenation, disproportionation, dimerization, esterification, etc. One type may be used alone, or two or more types may be used in combination.

[0138] Phenolic resins Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, oil-modified phenol-formaldehyde resin, etc. They may be used individually or in combination of two or more.

[0139] Coumaron-based resin Coumaron-based resins are resins whose main component is coumaron. Examples include coumaron resin, coumaron-indene resin, and copolymer resins whose main components are coumaron, indene, and styrene. They may be used individually or in combination of two or more types.

[0140] ≪Resin content≫ From the viewpoint of adhesive performance and grip performance, the content of the rubber component in the resin per 100 parts by mass is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. Furthermore, from the viewpoint of abrasion resistance and grip performance, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less.

[0141] ≪Softening point of resin≫ From the viewpoint of grip performance, the softening point of the resin is preferably 160°C or lower, more preferably 145°C or lower, and even more preferably 130°C or lower. Furthermore, from the viewpoint of grip performance, the softening point is preferably 20°C or higher, more preferably 35°C or higher, even more preferably 50°C or higher, and even more preferably 80°C or higher. The softening point is measured by the method described above.

[0142] Weight-average molecular weight of resins The weight-average molecular weight (Mw) of the resin is preferably 300 or higher, more preferably 400 or higher, and even more preferably 500 or higher, as it is less volatile and has good grip performance. Furthermore, the Mw is preferably 15,000 or lower, more preferably 10,000 or lower, and even more preferably 8,000 or lower. The weight-average molecular weight (Mw) can be determined by the method described above.

[0143] <SP value of resin> The SP value of the resin is preferably in the range of 8 to 11, more preferably in the range of 8 to 10, and even more preferably in the range of 8.3 to 9.5, due to its excellent compatibility with rubber components (especially SBR). By using a resin with an SP value within the above range, the compatibility with SBR and BR is improved, and the wear resistance and elongation at break can be improved. The SP value is calculated by the method described above.

[0144] (Liquid polymer) The liquid polymer is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25°C), but examples include liquid diene polymers such as liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), and liquid styrene-isoprene copolymer (liquid SIR). The liquid polymer may be used alone or in combination of two or more. Among these, liquid SBR is preferred from the viewpoint of grip performance. The molecular weight of the liquid polymer is 1.0 × 10⁻¹⁶, measured by gel permeation chromatography (GPC) with a polystyrene-equivalent weight-average molecular weight. 3 ~2.0×10 5 This is preferable. The weight-average molecular weight (Mw) can be determined by the method described above.

[0145] When a liquid polymer is included, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, and more preferably 5 parts by mass or more, from the viewpoint of grip performance. Furthermore, from the viewpoint of abrasion resistance, it is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less.

[0146] (wax) The wax used can be one that is commonly used in the tire industry, and may be used alone or in combination of two or more types. When wax is included, the amount of wax per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of weather resistance of the rubber. Furthermore, from the viewpoint of suppressing whitening of the tire due to bloom, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0147] (Processing aid) Processing aids can be those commonly used in the tire industry, such as fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. These may be used individually or in combination of two or more. When processing aids are included, the content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of improving processability. Furthermore, from the viewpoint of wear resistance and fracture strength, it is preferably 10 parts by mass or less, and more preferably 8 parts by mass or less.

[0148] (Anti-aging agent) Anti-aging agents that are commonly used in the tire industry can be used. Specifically, examples include amine-based, quinoline-based, quinone-based, phenol-based, imidazole-based, and phenylenediamine-based compounds, as well as metal carbamate salts. Among these, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, and N,N'-bis(1-ethyl-3-methylpentyl) Phenylenediamine-based antioxidants such as phenyl((-p-phenylenediamine), N-4-methyl-2-pentyl-N'-phenyl-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine, hindereddiaryl-p-phenylenediamine, phenylhexyl-p-phenylenediamine, and phenyloctyl-p-phenylenediamine, and quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These antioxidants may be used alone or in combination of two or more.

[0149] When an anti-aging agent is included, the content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, or even 1 part by mass or more, from the viewpoint of the rubber's resistance to ozone cracking. Furthermore, from the viewpoint of wear resistance and wet grip performance, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0150] (Stearic acid) When stearic acid is included, its content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0151] (Zinc oxide) When zinc oxide is included, its content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of wear resistance, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0152] (Inorganic potassium salts) Inorganic potassium salts that are commonly used in the tire industry can be used, and may be used alone or in combination of two or more. Examples of inorganic potassium salts include one or more potassium salts selected from the group consisting of potassium carbonate, potassium bicarbonate, and potassium tetraborate, of which potassium tetraborate is preferred.

[0153] From the viewpoint of extrusion processability, the inorganic potassium salt content is preferably 0.3 parts by mass or more, more preferably 0.4 parts by mass or more, per 100 parts by mass of silica. Furthermore, from the viewpoint of wear resistance, the content is preferably 3 parts by mass or less, more preferably 2.5 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1.45 parts by mass or less, per 100 parts by mass of silica.

[0154] (Vulcanizing agent) Sulfur is preferably used as a vulcanizing agent. Suitable sulfurs include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Each type may be used individually or in combination of two or more.

[0155] Examples of vulcanizing agents other than sulfur include sulfur-containing vulcanizing agents such as 1,6-hexamethylene-dithiosulfate sodium dihydrate and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, as well as organic peroxides such as dicumyl peroxide. Examples of vulcanizing agents other than sulfur include those manufactured by Taoka Chemical Industries, Ltd., Flexis, and Lanxess.

[0156] When sulfur is included as a vulcanizing agent, the amount of sulfur per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 0.7 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction and obtaining good grip performance and abrasion resistance. Furthermore, from the viewpoint of suppressing deterioration, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0157] (Vulcanization accelerator) Examples of vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamate, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. Among these, at least one of sulfenamide, guanidine, and thiazole is preferred, and the combination of sulfenamide and guanidine is more preferred.

[0158] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (DCBS). Among these, N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS) is preferred.

[0159] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salts of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0160] Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and di-2-benzothiazolyl disulfide. Among these, 2-mercaptobenzothiazole is preferred.

[0161] When a vulcanization accelerator is included, its content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, and more preferably 2 parts by mass or more. Furthermore, the content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less. By keeping the content of the vulcanization accelerator within the above range, it tends to be possible to ensure fracture strength and elongation.

[0162] <Manufacturing method> [Manufacturing of rubber compositions] As a method for producing the rubber composition of this disclosure, any known method may be applied as appropriate. For example, the composition can be produced by kneading each of the above components using a rubber kneading device such as an open roll or a closed kneader (Banbury mixer, kneader, etc.). The kneading process includes, for example, a base kneading step in which compounding agents and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading step and kneaded. Furthermore, the base kneading step can be divided into multiple steps if desired. The kneading conditions are not particularly limited, but for example, in the base kneading step, kneading is performed at a discharge temperature of 150 to 170°C for 3 to 10 minutes, and in the final kneading step, kneading is performed at 50 to 110°C for 1 to 5 minutes.

[0163] When manufacturing the rubber composition of this disclosure using the aforementioned components, the proportions of each component can be appropriately determined according to the physical properties of the rubber composition constituting the crown portion and the rubber composition constituting the shoulder portion.

[0164] [Tire manufacturing] The rubber composition obtained above can be extruded to the desired tread shape at the unvulcanized stage and molded together with other tire components in a conventional manner on a tire molding machine to produce an unvulcanized tire. By heating and pressurizing (vulcanizing) this unvulcanized tire in a vulcanizing machine, the motorcycle tire of this disclosure can be obtained. The vulcanization conditions are not particularly limited, and for example, a method of vulcanization at 150 to 200°C for 5 to 30 minutes can be used.

[0165] <Application> The motorcycle tire disclosed herein is not particularly limited in form and may be either a pneumatic tire or a solid tire, but it is preferable to use it as a pneumatic tire. It can also be used for various applications such as on-road tires, off-road tires, and racing tires. [Examples]

[0166] The present disclosure will be described in detail below based on examples, but the present disclosure is not limited to these examples.

[0167] <Various chemicals> SBR1: TUFDENE 4850 (Unmodified S-SBR from Asahi Kasei Corporation, styrene content: 40% by mass, vinyl bond content: 46%, Tg: -25℃, contains 50 parts by mass of oil-expanding oil per 100 parts by mass of rubber solids) SBR2: TUFDENE 3830 (Unmodified S-SBR from Asahi Kasei Corporation, styrene content: 33% by mass, vinyl bond content: 34%, Tg: -39℃, contains 37.5 parts by mass of oil-expanding oil per 100 parts by mass of rubber solids) BR1: Ubepol BR150B (High-cis BR synthesized using a Co-based catalyst, manufactured by Ube Industries, Ltd., cis content: 97%, vinyl bond content: 1%, Tg: -107℃) Carbon Black 1: Show Black N110 (available from Cabot Japan Co., Ltd., N2SA: 142m) 2 / g (BET value), DBP oil absorption: 115mL / 100g) Silica 1: Ultrasil VN3 (available from Ebonig Degussa, N2SA: 175m) 2 / g (BET value)) Silane coupling agent 1: Si69 (manufactured by Evonig Degussa, bis(3-(triethoxysilyl)propyl)tetrasulfide) Oil: Diana Process NH-70S (Aromatic process oil from Idemitsu Kosan Co., Ltd.) Resin: Sylvatraxx 4401 (Aromatic petroleum resin from Kraton Corporation (α-methylstyrene resin: copolymer of α-methylstyrene and styrene), softening point 85°C, SP value: 9.1) Wax: Ozoace 0355 (available from Nippon Seiro Co., Ltd.) Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, available from Sumitomo Chemical Co., Ltd.) Stearic acid: Stearic acid "Tsubaki" (available from NOF Corporation) Zinc oxide: Ginrei R (available from Toho Zinc Co., Ltd.) Sulfur: HK-200-5 (5% oil-containing sulfur powder from Hosoi Chemical Industry Co., Ltd.) Vulcanization accelerator 1: Noxellar NS-P (N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), available from Ouchi Shinko Chemical Co., Ltd.) Vulcanization accelerator 2: Noxellar D (1,3-diphenylguanidine (DPG), available from Ouchi Shinko Chemical Industry Co., Ltd.)

[0168] <Manufacturing of test tires> According to the formulations (C1-C7) for the crown rubber composition shown in Table 1, chemicals other than sulfur and vulcanization accelerator were mixed for 5 minutes at a discharge temperature of 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. Next, sulfur and vulcanization accelerator were added to the resulting mixture and kneaded in an open roll for 4 minutes until the temperature reached 105°C to obtain an unvulcanized rubber composition for the crown.

[0169] On the other hand, an unvulcanized rubber composition for the shoulder portion was obtained by processing it in the same manner as for the crown portion, according to the compound formulations (S1 to S6) for the shoulder portion shown in Table 1.

[0170] Test tires having the basic structure shown in Figure 1 and the basic pattern shown in Figure 4 or Figure 5 were manufactured according to the specifications in Table 2. Specifically, the unvulcanized rubber composition for the crown and the unvulcanized rubber composition for the shoulder obtained above were molded into the shape of the crown and a pair of shoulders of the tread, respectively, and bonded together with other tire components to produce an unvulcanized tire. This tire was then press-vulcanized at 170°C for 12 minutes to obtain a test tire. The test tire had a front tire size of 120 / 70ZR17 and a rear tire size of 180 / 55ZR17.

[0171] <Measurement and Evaluation> Each measurement and evaluation was performed according to the method described below. The results are shown in Tables 1 and 3.

[0172] [tanδ] Using the Iplexer series from GABO, the tanδ at 0°C was measured under conditions of 0°C, 10Hz frequency, 10% initial strain, and 2.5% dynamic strain in extension mode, while the tanδ at 70°C was measured under conditions of 70°C, 10Hz frequency, 10% initial strain, and 1% dynamic strain in extension mode. The sample used for measurement was a vulcanized rubber composition measuring 20mm in length, 4mm in width, and 1mm in thickness, prepared by cutting a section of the tire tread with the tire's circumferential direction as the longitudinal direction.

[0173] [tanδ peak temperature] The tanδ peak temperature of the vulcanized rubber composition was determined by measuring the tanδ temperature distribution curve using a GABO Iplexer series analyzer under conditions of a frequency of 10 Hz, initial strain of 10%, dynamic strain of ±0.5%, and heating rate of 2°C / min. The temperature corresponding to the largest tanδ value in the obtained temperature distribution curve was then determined as the tanδ peak temperature. The sample used for measurement was a vulcanized rubber composition measuring 20 mm in length, 4 mm in width, and 1 mm in thickness, prepared by cutting a section of the tire tread with the tire's circumferential direction as the longitudinal direction.

[0174] [hardness] The hardness of the vulcanized rubber composition was measured by cutting a tread portion from the tread area that forms the contact surface of the test tire, such that the tire radius direction is the thickness direction, creating a hardness measurement sample, and then pressing a Type A durometer onto the sample from the contact surface side at 23°C in accordance with JIS K 6253 to measure the hardness.

[0175] [M300] For the M300 test, a 1mm thick, No. 7 dumbbell-shaped test specimen was prepared by cutting it from the inside of the rubber layer of the tread portion of each test tire so that the circumferential direction of the tire was the tensile direction. A tensile test was performed in accordance with JIS K 6251 "Vulcanized rubber and thermoplastic rubber - Method for determining tensile test properties" at a 23°C atmosphere and a tensile speed of 3.3 mm / second, and the stress at 300% elongation (M300) (MPa) was determined.

[0176] [Dry peel resistance] Each test tire was mounted on a standard rim (front wheel: MT3.50x17, rear wheel: MT5.50x17) and fitted to a test vehicle (750cc four-stroke motorcycle). The internal air pressure was adjusted to 250kPa for the front tire and 290kPa for the rear tire.

[0177] This test vehicle was driven 5,000 km on a dry asphalt test course, and the degree of delamination at the interface between the crown and shoulder of the tread was visually evaluated. The results were expressed as an index, with the reference comparison set to 100. A higher number indicates better performance.

[0178] [Wet crack resistance] The above test vehicle was driven 5000km on a wet asphalt test course, and the occurrence of cracks in the tread was visually evaluated. The results were expressed as an index, with the reference comparison set to 100. A higher number indicates better performance.

[0179] [Table 1]

[0180] [Table 2]

[0181] [Table 3]

[0182] Table 3 shows that the sum of the indices for dry peel resistance and wet crack resistance has improved in the motorcycle tires of this disclosure.

[0183] <Embodiment> Examples of embodiments of this disclosure are shown below.

[0184] [1] A motorcycle tire comprising a crown portion located in the center in the axial direction of the tire and a pair of shoulder portions located outside the crown portion, The tanδ(70°C tanδ) of the rubber composition constituting the crown portion Cr ) is the tanδ(70℃tanδ) of the rubber composition constituting the shoulder portion at 70℃. Sh Larger than ) The tanδ(0°C tanδ) of the rubber composition constituting the crown portion at 0°C Cr ) is the tanδ(0℃tanδ) of the rubber composition constituting the shoulder portion at 0℃. Sh Smaller than ) The tread surface of the tread portion is provided with grooves, A motorcycle tire in which the groove straddles the boundary between the crown portion and the shoulder portion, but does not straddle the equator. [2] The motorcycle tire according to [1] above, wherein the groove depth D (mm) of the groove with the largest groove depth satisfies the following formula (1), preferably the value of the right-hand side of the following formula (1) is 1.30, more preferably the value of the right-hand side of the following formula (1) is 1.40, and even more preferably the value of the right-hand side of the following formula (1) is 1.50. Formula (1): D×70℃tanδ Cr >1.20 [3] A motorcycle tire according to [1] or [2] above, wherein the groove width W (mm) of the groove with the largest groove width satisfies the following formula (2), preferably the value of the right-hand side of the following formula (2) is 0.90, more preferably the value of the right-hand side of the following formula (2) is 1.00, and even more preferably the value of the right-hand side of the following formula (2) is 1.10. Formula (2): W×70℃tanδ Cr >0.80 [4] Of the grooves, the circumferential length component L of the groove with the largest circumferential length component C A motorcycle tire according to any of the above [1] to [3], wherein (mm) satisfies the following formula (3), preferably the value of the right-hand side of the following formula (3) is 0.06, more preferably the value of the right-hand side of the following formula (3) is 0.07, and even more preferably the value of the right-hand side of the following formula (3) is 0.08. Formula (3):L C ×(70℃ tanδ Cr -70℃ tanδ Sh )>0.05 [5] A motorcycle tire according to any of [1] to [4] above, wherein the groove with the smallest groove bottom thickness H (mm) satisfies the following formula (4), preferably the value of the right-hand side of the following formula (4) is 1.4, more preferably the value of the right-hand side of the following formula (4) is 1.5, and even more preferably the value of the right-hand side of the following formula (4) is 1.6. Equation (4): H / 0℃tanδ Cr >1.3 [6] The groove cross-sectional area S (mm²) of the groove with the largest groove cross-sectional area among the grooves. 2A motorcycle tire according to any of the above [1] to [5], wherein the following formula (5) is satisfied, preferably the value of the right-hand side of the following formula (5) is 140, more preferably the value of the right-hand side of the following formula (5) is 130, and even more preferably the value of the right-hand side of the following formula (5) is 120. Equation (5):S / (0℃tanδ Sh -0℃ tanδ Cr )<150 [7] The tanδ peak temperature (T) of the rubber composition constituting the crown portion Cr ) is the tanδ peak temperature (T) of the rubber composition constituting the shoulder portion. Sh ) lower than, preferably T Cr is T Sh A motorcycle tire described in any of the above [1] to [6], which is 1°C or more cooler. [8] The motorcycle tire according to any one of [1] to [7] above, wherein the hardness of the rubber composition constituting the crown portion is greater than, preferably by 3 or more, and more preferably by 5 or more, the hardness of the rubber composition constituting the shoulder portion. [9] The stress of the rubber composition constituting the crown portion at 300% elongation (M300 Cr ) is the stress of the rubber composition constituting the shoulder portion at 300% elongation (M300 Sh Larger than ) preferably M300 Cr M300 Sh It is 110% or more of M300 Cr M300 Sh A motorcycle tire described in any of the above [1] to [8], which is 120% or more of the above. [Explanation of Symbols]

[0185] 1. Motorcycle tires 2 Tread section 2A Tread surface 2e tread edge 3. Sidewall section 4. Bead section 5 Bead core 6 Carcass 7 Belt layer 8 Bead Apex 9 Tread Rubber 9A Crown section 9B Shoulder section 100 road surface C equator D Groove depth H groove bottom thickness L C Circumferential length component of the groove S groove cross-sectional area W groove width X Width of the contact surface Y-cutting line TW Tread width Cr Crown Sh Shoulder section R Tire rotation direction

Claims

1. A motorcycle tire comprising a tread portion having a crown portion located in the center in the tire axial direction and a pair of shoulder portions located outside the crown portion, The tanδ of the rubber composition constituting the crown portion at 70°C (70°C tanδ Cr ) is the tanδ at 70°C of the rubber composition constituting the shoulder portion (70°C tanδ Sh Larger than ) The tanδ of the rubber composition constituting the crown portion at 0°C (0°C tanδ Cr ) is the tanδ at 0°C of the rubber composition constituting the shoulder portion (0°C tanδ Sh Smaller than ) The tread surface of the tread portion is provided with grooves, A motorcycle tire in which the groove straddles the boundary between the crown portion and the shoulder portion, but does not straddle the equator.

2. The motorcycle tire according to claim 1, wherein the groove depth D (mm) of the groove with the maximum groove depth among the grooves satisfies the following formula (1). Equation (1): D×70℃tanδ Cr >1.20

3. The motorcycle tire according to claim 1 or 2, wherein the groove width W (mm) of the groove with the largest groove width among the grooves satisfies the following formula (2). Equation (2): W×70℃tanδ Cr >0.80

4. Of the grooves, the circumferential length component L of the groove with the largest circumferential length component. C A motorcycle tire according to any one of claims 1 to 3, wherein (mm) satisfies the following formula (3). Formula (3): L C × (tan δ at 70°C Cr − tan δ at 70°C Sh ) > 0.05

5. A motorcycle tire according to any one of claims 1 to 4, wherein the thickness H (mm) of the groove with the minimum groove bottom thickness among the grooves satisfies the following formula (4). Equation (4): H / 0℃ tanδ Cr >1.3

6. Of the grooves, the groove with the largest cross-sectional area S (mm²) 2 A motorcycle tire according to any one of claims 1 to 5, wherein the tire satisfies the following formula (5). Formula (5): S / (0 °C tan δ Sh - 0 °C tan δ Cr ) < 150

7. The tanδ peak temperature (T) of the rubber composition constituting the crown portion Cr ) is the tanδ peak temperature (T) of the rubber composition constituting the shoulder portion. Sh A motorcycle tire according to any one of claims 1 to 6, which is lower than ).

8. A motorcycle tire according to any one of claims 1 to 7, wherein the hardness of the rubber composition constituting the crown portion at 23°C is greater than the hardness of the rubber composition constituting the shoulder portion at 23°C.

9. The stress of the rubber composition constituting the crown portion at 300% elongation at 23°C (M300) Cr ) is the stress of the rubber composition constituting the shoulder portion at 300% elongation at 23°C (M300 Sh A motorcycle tire according to any one of claims 1 to 8, which is larger than ).

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