RUBBER COMPOSITION AND TIRE WITH TREAD CONTAINING FUNCTIONALIZED POLYBUTADIENE RUBBER AND REINFORCING FILLER CONTAINING PRECIPITATED SILICA

A rubber composition and a tire comprising such a rubber composition is disclosed. The rubber composition comprises based on parts by weight per 100 parts by weight of the tread rubber (phr): (A) conjugated elastomer(s) comprising: (1) from 40 to 100 phr of a cis 1,4-polybutadiene rubber, wherein said cis 1,4-polybudiene rubber comprises: (a) from 40 to 100 weight percent of a functionalized cis 1,4-polybutadiene rubber, wherein said functionalized cis 1,4-polybutadiene rubber is: (b) from 0 to 60 weight percent of a non-functionalized cis 1,4-polybutadiene rubber, and (B) from 40 to 110 phr of a reinforcing filler comprising a combination of precipitated silica and a carbon black; wherein the precipitated silica is: (3) hydrophobated by reaction with said coupling agent in situ within said rubber composition rubber composition, or (4) pre-hydrophobated by reaction with said coupling prior to addition to said rubber composition; and wherein the coupling agent for the hydrophobation of the precipitated silica comprises bis (3-trialkoxysilylpropyl) polysulfide containing an average of from 2 to 3.8 connecting sulfur atoms in its polysulfidic bridge or an alkoxyorganomercaptosilane.