Tire with tread of cis 1,4-polybutadiene rich rubber composition which contains a functional styrene/butadiene elastomer, silica and coupling agent

Abstract

The invention relates to a tire having a tread of a rubber composition comprised of a composite of styrene/butadiene elastomer and functionalized styrene/butadiene elastomer containing an internal silanol and/or siloxy group therein with pendent silanol and/or alkoxy groups of a polymodal (e.g. bimodal) molecular weight distribution, together with at least 30 phr of cis 1,4-polybutadiene rubber and a dispersion in said rubber composition of precipitated silica aggregates and a coupling agent as a bis (3-triethoxysilylpropyl) polysulfide having an average of from only 2 to 2.5 sulfur atoms in its polysulfidic bridge to the exclusion of a bis (3-trialkoxysilylalkyl) polysulfide having an average of greater than 2.5, and particularly greater than 3, sulfur atoms in its polysulfidic bridge. In one aspect, said silica aggregates may be pre-treated to reduce said hydroxyl groups on their surface prior to blending with said silanol and/or siloxy functionalized elastomer. In one aspect, a carbon black contained in the rubber composition may be an electrically conductive carbon black.