Patent ID: 7211630

Claim:
A rubber composition comprising a rubber component formed by compounding a styrene-butadiene copolymer (A) polymerized with a lithium based polymerization initiator, in which a polystyrene-conversion weight average molecular weight through a gel permeation chromatography is 4.0×10 5 −3.0×10 6 and a bound styrene content is 10–50 mass % and a vinyl bond content in butadiene portion is 20–70%, with 10–200 parts by mass of a hydrogenated styrene-isoprene copolymer (B) based on 100 parts by mass of the copolymer (A), in which a polystyrene-conversion weight average molecular weight through a gel permeation chromatography is 5.0×10 3 −2.0×10 5 and a bound styrene content is 25–70 mass % and not less than 60% of double bond in isoprene portion is hydrogenated, and having a relation between the bound styrene content of the polymer (A) and the bound styrene content of the polymer (B) satisfying the following equation: Bound styrene content of polymer (B)>bound styrene content of polymer (A)+10 (mass %).