Bridgestone Tire Company Limited

Noboru Kusakabe

Koichi Kojima

Masaaki Morimoto

Eiichi Koyama

Nobumasa Ikeda

A pneumatic radial tire comprising a carcass of a radial structure and a belt superimposed about a crown portion of the carcass is disclosed. The belt is composed of at least one open-twisted steel cord layer formed by embedding open-twisted steel cords. Each cord is composed of 4-5 steel filaments and having an elongation of 0.2-0.7% under a load of 5 kg/cord and a twisting pitch of 8-16 mm, in a coating rubber having a 100% modulus of 30-70 kg/cm.sup.2.

Pneumatic radial tires

A composite material of rubber and metal cords embedded therein is disclosed. The metal cord is produced by twisting at least three metal filaments, and has an elongation under a load of 5.0 kg/cord (P.sub.1) of 0.2-1.2% and an elongation under a load of 2.0 kg/cord (P.sub.2, %) of P.sub.2 .ltoreq.0.947P.sub.1 -0.043 prior to the embedding in rubber.

Metal cord-rubber composite materials

A rubber composition containing polyisoprene rubber or a blend of polyisoprene rubber and polybutadiene rubber has a high friction coefficient against the frozen road surface due to the easy deformability at low temperature and high affinity for water. A pneumatic tire comprising a tread consisting of the rubber composition is excellent in the brake, traction and cornering performances and can travel safely on frozen roads without the use of spikes or a chain.

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Ohme, Japan

Noboru Kusakabe