A rubber composition is disclosed. comprising, based on parts by weight per 100 parts by weight rubber (phr): (A) 100 phr of at least one conjugated diene-based elastomer which includes: (1) 20 to 100 phr of a functionalized styrene/butadiene elastomer derived from organic solvent solution polymerization of styrene and 1,3-butadiene monomers which contains 10 to 50 percent bound styrene and has a vinyl 1,2-content based on its butadiene component in a range of from 10 to 70 percent, said functionalized styrene/butadiene elastomer comprising: (a) 10 to 50 phr of a first functionalized styrene/butadiene elastomer containing functional groups comprising siloxy and amine groups reactive with hydroxyl groups on a silica, and (b) 10 to 50 phr of a second functionalized styrene/butadiene elastomer containing functional groups comprising siloxy and thiol groups reactive with hydroxyl groups on a silica; (B) 10 to 170 phr of a particulate rubber reinforcing filler; and (C) 0.1 to 10 phr of a zinc salt of a fatty acid soap. [0002] Also a pneumatic tire comprising such a rubber composition in its tread is disclosed.
