| abstract |
A pneumatic tire having a tread is disclosed, which comprises using in said tread a rubber composition containing 10 to 120 parts by weight of carbon black and 0.5 to 5 parts by weight of a vulcanizer based on 100 parts by weight of a novel styrene-butadiene copolymer rubber as defined below alone or a blend rubber of not less than 30 parts by weight of said copolymer rubber and not more than 70 parts by weight of the other diene rubber, said styrene-butadiene copolymer rubber being obtained by random copolymerization of styrene with 1,3-butadiene and satisfying the following requirements: (1) a content of bound styrene is 10 to 30% by weight; (2) a content of 1,2-bond in butadiene portion is 42 to 70% by weight; (3) a content of trans-1,4 bond in butadiene portion is not less than 25% by weight; (4) a value obtained by subtracting a content of cis-1,4 bond in butadiene portion from said content of trans-1,4 bond is not less than 8% by weight; (5) a relation between said content of bound styrene and said content of 1,2-bond is 65</=1.7x the content of bound styrene (% by weight) + the content of 1,2-bond (% by weight) </=100; (6) a weight mean molecular weight (Mw) is 35x104 to 65x104; (7) a ratio of weight mean molecular weight (Mw) to number mean molecular weight (Mn) is not more than 2. |