RUBBER COMPOSITION FOR TIRE TREADS

Rubber compositions for tire treads. Typically, they contain a rubber component containing at least 70 parts by weight of a styrene-butadiene rubber whose styrene content is 20 to 60%; and contain, based on 100 parts by weight of the rubber component, 5 to 150 parts by weight of a powdery inorganic compound represented by formula (I) and having a particle size from 0.01 to 10 m: mM 1 .x SiO y.z H 2 O (I) in which M 1 is at least one selected from the group consisting of hydroxides of Al, Mg, Ti, and Ca; and m, x, y, and z are integers from 1 to 5, 0 to 10, 2 to 5, and 0 to 10, respectively; and 5 to 170 parts by weight of carbon black having a nitrogen adsorption specific area of 80 to 280 m 2 /g so that the total amount of the powdery inorganic compound and the carbon black falls in the range of 70 to 200 parts by weight. The amount of an extract obtained by extracting the rubber composition after being vulcanized from acetone and chloroform should be 30 to 270 parts by weight. Similar compositions containing silica are also disclosed.