Abstract: A rubber composition for a tire comprising:100 parts by weight of a starting rubber;10 to 150 parts by weight of a carbon black;0.1 to 20 parts by weight of a sulfur; and40 parts by weight or less of a polysiloxanehaving the following alkoxysilyl group (I) or acyloxysilyl group (II) and having an average degree of polymerization of 3 to 10,000:.tbd.Si--OR.sup.1 (I).tbd.Si--OCOR.sup.2 (II)wherein R.sup.1 is a substituted or unsubstituted monovalent hydrocarbon group or an organic group containing an ether bond and having 1 to 18 carbon atoms and R.sup.2 is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms.

Abstract: A pneumatic tire in which the cap tread portion is composed of a rubber composition comprising (i) 100 parts by weight of a diene rubber having a glass transition temperature (Tg) of not more than -45.degree. C. and (ii) not more than 65 parts by weight of carbon black having a nitrogen specific surface area (N.sub.2 SA) of not less than 140 m.sup.2 /g, a DBP oil absorption of not less than 120 ml/100 g, a .DELTA.DBP of not less than 30 ml/100 g, and a half value (.DELTA.Dst) of distribution of aggregates, measured by a centrifugal precipitation method, of not more than 50 m.mu., or a pneumatic tire in which a cap tread portion is composed of a rubber composition comprising (A) 100 parts by weight of a rubber component mainly comprising natural rubber and polybutadiene rubber and having a hardness at 0.degree. C. of not more than 60 and (B) (i) carbon black having a nitrogen specific surface area (N.sub.2 SA) of not less than 120 m.sup.

Abstract: The cap tread portion composed of a rubber composition having a tan.delta. (0.degree. C.) of at least 0.45 and a tan.delta. (60.degree. C.) of at least 0.25 comprising (i) a p-phenylenediamine type antioxidant, 2,2,4-trimethyl-1,2-dihydroquinoline etc, and carbon black having a nitrogen specific surface area of at least 70 m.sup.2 /g and a 24M4DBP of at least 80 ml/100 g or (ii) a p-phenylenediamine based antioxidant, a 2,2,4-trimethyl-1,2-dihydroquinoline or other polymer mixture of a specific polymer content, and carbon black having a nitrogen specific surface area of at least 70 m.sup.2 /g and a 24M4DBP of at least 80 ml/100 g, blended with a rubber.

Abstract: A pneumatic tire having a tread composed of a matrix rubber, a low hardness rubber powder, hollow particulates, and short fibers, and optionally a liquid polymer, wherein the low hardness rubber powder has an average particle size of less than 1000 .mu.m, including or not including no more than 20 parts by weight of carbon per 100 parts by weight of the rubber component in the low hardness rubber powder, and is contained in an amount of 1 to 10 parts by weight per 100 parts by weight of the matrix rubber, the hollow particulates have an average particle size of 10 to 120 .mu.m and an average thickness of 0.1 to 15 .mu.m, and the short fibers have an aspect ratio (ratio of length/diameter) of 10 to 1000.

Abstract: Rubber compositions for tire treads of an all-weather type are disclosed which are so designed as to exhibit high dynamic Young's modulus, sufficient resistance to snow and ice skidding, to abrasion, to cracking and to crack growth and adequate durability. A selected base rubber is combined with a selected carbon black and a selected m-cresol resin. The base rubber is a blend of two different rubbers, one being natural rubber alone or a combination with a diene rubber and the other being butadiene rubber. The carbon black has specified absorptivity of iodine and dibutyl phthalate. The m-cresol resin is a novolak condensate.