The present disclosure aims to provide rubber compositions and tires which provide improved overall performance in terms of wet grip performance and dry grip performance. The present disclosure relates to a rubber composition having a hardness that reversibly changes with water and satisfying the following relationships (1) and (2): Hardness when dry−Hardness when water-wet≥1 (1) wherein each hardness represents the JIS-A hardness at 25° C. of the rubber composition; and tan δ at 70° C. when dry≥0.18 (2) wherein the tan δ at 70° C. represents the loss tangent measured at 70° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz.

The present disclosure aims to provide rubber compositions and tires which provide improved overall performance in terms of wet grip performance and dry grip performance. The present disclosure relates to a rubber composition having a hardness that reversibly changes with water and satisfying the following relationships (1) and (2): Hardness when dry−Hardness when water-wet≥1 (1) wherein each hardness represents the JIS-A hardness at 25° C. of the rubber composition; and tan δ at 70° C. when dry≥0.18 (2) wherein the tan δ at 70° C. represents the loss tangent measured at 70° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz.

The present invention is directed to a pneumatic tire having a tread comprising a vulcanizable rubber composition comprising, based on 100 parts by weight of elastomer (phr), up to 100 phr of a solution polymerized styrene-butadiene rubber; from 5 to 50 phr of a fatty acid monoester of formula 1

##STR00001##

where R.sup.1 is selected from C1 to C8 linear or branched alkyl, C1 to C8 linear or branched alkenyl, and C2 to C6 linear or branched alkyl substituted with from one to five hydroxyl groups; R.sup.2 is C11 to C21 alkyl or C11 to C21 alkenyl; from 5 to 50 phr of a hydrocarbon resin having a Tg ranging from −40° C. to 20° C.; less than 10 phr of a petroleum-derived oil; and from 50 to 130 phr of silica. optionally, from about 1 to 50 phr carbon black.

The present invention is directed to a pneumatic tire having a tread comprising a vulcanizable rubber composition comprising, based on 100 parts by weight of elastomer (phr), up to 100 phr of a solution polymerized styrene-butadiene rubber; from 5 to 50 phr of a fatty acid monoester of formula 1

##STR00001##

where R.sup.1 is selected from C1 to C8 linear or branched alkyl, C1 to C8 linear or branched alkenyl, and C2 to C6 linear or branched alkyl substituted with from one to five hydroxyl groups; R.sup.2 is C11 to C21 alkyl or C11 to C21 alkenyl; from 5 to 50 phr of a hydrocarbon resin having a Tg ranging from −40° C. to 20° C.; less than 10 phr of a petroleum-derived oil; and from 50 to 130 phr of silica. optionally, from about 1 to 50 phr carbon black.

The present invention is directed to a pneumatic tire having a tread comprising a vulcanizable rubber composition comprising, based on 100 parts by weight of elastomer (phr), up to 100 phr of a solution polymerized styrene-butadiene rubber; from 5 to 50 phr of a fatty acid monoester of formula 1

##STR00001##

where R.sup.1 is selected from C1 to C8 linear or branched alkyl, C1 to C8 linear or branched alkenyl, and C2 to C6 linear or branched alkyl substituted with from one to five hydroxyl groups; R.sup.2 is C11 to C21 alkyl or C11 to C21 alkenyl; from 5 to 50 phr of a hydrocarbon resin having a Tg ranging from −40° C. to 20° C.; less than 10 phr of a petroleum-derived oil; and from 50 to 130 phr of silica. optionally, from about 1 to 50 phr carbon black.

The present invention relates to a cross-linkable rubber composition for body compounds of a tyre, the cross-linkable rubber composition comprising, based upon parts by weight per 100 parts by weight rubber (phr): ≥30 to ≤90 phr of a natural rubber or isoprene rubber or combination thereof, ≥10 to ≤25 phr of a syndiotactic 1, 2-polybutadiene, ≥3 to ≤10 phr of a resin, and a filler, wherein the ratio in phr (parts by weight per 100 parts by weight of rubber) of the syndiotactic 1, 2-polybutadiene to the resin is in the range of ≥1:1 to ≤7:1.

The present invention relates to a cross-linkable rubber composition for body compounds of a tyre, the cross-linkable rubber composition comprising, based upon parts by weight per 100 parts by weight rubber (phr): ≥30 to ≤90 phr of a natural rubber or isoprene rubber or combination thereof, ≥10 to ≤25 phr of a syndiotactic 1, 2-polybutadiene, ≥3 to ≤10 phr of a resin, and a filler, wherein the ratio in phr (parts by weight per 100 parts by weight of rubber) of the syndiotactic 1, 2-polybutadiene to the resin is in the range of ≥1:1 to ≤7:1.

The present invention provides a tread rubber composition that is excellent in wet grip performance during the initial phase of running and tensile properties, and a pneumatic tire including the tread rubber composition. The present invention relates to a tread rubber composition containing: a diene rubber; silica; and sulfur and/or a sulfur-containing compound, the tread rubber composition satisfying the following relationships (1) to (3):
EB/M300≥50  (1);
M100≥1.7 MPa  (2); and
EB≥500%  (3).

The present invention provides a tread rubber composition that is excellent in wet grip performance during the initial phase of running and tensile properties, and a pneumatic tire including the tread rubber composition. The present invention relates to a tread rubber composition containing: a diene rubber; silica; and sulfur and/or a sulfur-containing compound, the tread rubber composition satisfying the following relationships (1) to (3):
EB/M300≥50  (1);
M100≥1.7 MPa  (2); and
EB≥500%  (3).

The present invention provides pneumatic tires which have reduced changes in hardness over time and which provide improved abrasion resistance while ensuring good durability. The present invention relates to a pneumatic tire formed from a rubber composition, the rubber composition containing: a rubber component including a hydrogenated copolymer containing a structural unit derived from an aromatic vinyl compound and a structural unit derived from a conjugated diene compound; and a liquid polymer having a number average molecular weight of 2,500 to 500,000, the hydrogenated copolymer being present in an amount of 80% by mass or less based on 100% by mass of the rubber component, the liquid polymer being present in an amount of 1 to 50 parts by mass per 100 parts by mass of the rubber component.