Bridgestone Tire Company Limited

Itsuo Miyake

Nobumasa Ikeda

Motonori Bundo

Kazuaki Yuto

Toru Oniki

Keizo Okamoto

Akihiro Noda

A rubber composition comprising rubber, novolak-type phenolic resin and carbon black is very rigid and is adapted to be used as a bead filler rubber of a tire. Tires using the rubber composition are excellent in the high speed performance, lateral rigidity, ride feeling and durability.

Bead filler rubber composition

A pneumatic tire having remarkably low rolling resistance and high wet skid resistance without deteriorating the wear resistance is obtained by using in at least the ground-contact area of its tread, a rubber composition consisting essentially of 100 parts by weight of a mixed elastomer and 40-80 parts by weight of carbon black, the mixed elastomer consisting of 10-60 parts by weight of a solution-polymerized styrene-butadiene copolymer rubber having a bonded styrene content of 5-30% by weight and a trans-1,4 content in butadiene unit of not more than 45% by weight; 10-50 parts by weight of an emulsion-polymerized styrene-butadiene copolymer rubber having a bonded styrene content of 30-50% by weight; and 0-80 parts by weight of at least one rubber having a glass transition temperature of not higher than -50.degree. C., which is selected from the group consisting of natural rubber, synthetic polyisoprene rubber, polybutadiene rubber and an emulsion polymerized styrene-butadiene copolymer rubber having a bonded styrene content of 18-28% by weight. The use of carbon black having a specific surface area of 85-95 m.sup.2 /g, a dibutyl phthalate absorption value of 100-110 ml/100 g, a tinting strength of 95-105 and a half value width of at least 180 m.mu. in the size distribution curve of the aggregates is particularly effective for lowering the rolling resistance.

Pneumatic tire

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Kodaira, Japan

Itsuo Miyake