Patent ID: 7714055

Claim:
A pneumatic rubber tire having a circumferential rubber tread where said tread is a rubber composition comprised of a blend of, based on parts by weight per 100 parts by weight (phr), (A) conjugated diene-based elastomers comprised of (1) a major continuous rubber phase comprised of from 55 to about 85 phr of cis 1,4-polybutadiene rubber (BR) having a cis 1,4-microstructure content of at least 95 percent and a single Tg within a range of about −98° C. to about −107° C.; (2) a minor dispersed rubber phase comprised of about 15 to about 45 phr of at least one emulsion polymerization prepared elastomeric high styrene-containing styrene/butadiene copolymer rubber having a bound styrene content in a range of about 35 to about 55 percent and a single Tg within a range of from about −20° C. to about −45° C., as a composite thereof containing from about 1 to about 80 parts by weight of at least partially exfoliated, intercalated clay particles per 100 parts by weight of the styrene/butadiene copolymer rubber as a dispersion therein, wherein the Tg of said cis 1,4-polybutadiene elastomer major rubber phase is at least 55° C. lower than the Tg of said emulsion polymerization derived high styrene containing styrene/butadiene elastomer minor rubber phase; and (B) about 35 to about 110 phr of reinforcing filler comprised of from about 5 to about 105 phr amorphous silica and from about 5 to about 105 phr of high structure carbon black reinforcing filler; wherein said high structure carbon black is characterized by having an Iodine value in a range of about 116 to about 135, g/kg together with a DBP (dibutylphthalate) value in a range of about 125 to about 140, cm3/100 g; and, (C) a coupling agent having a moiety reactive with hydroxyl groups contained on the surface of said silica and said clay particles and another moiety interactive with at least one of said diene-based elastomers.