Bridgestone Tire Company Limited

Shigeta Aoki

Hiroshi Ogawa

Shigeo Makino

Hiroyoshi Takigawa

Shigeo Watanabe

Tatsuo Arai

Norboru Sugimura

A pneumatic radial tire for heavy vehicles comprising in combination two wide zigzag circumferential main grooves for dividing a tread into a center region and two side regions, a narrow zigzag groove for dividing each region into two portions, and a branch groove located in the center region and connected to the main and narrow grooves to define blocks and satisfying the following requirements, i.e.

Center block side rib tread pattern for heavy vehicle radial tires

A large-sized pneumatic radial tire is disclosed. This tire comprises a tread including grooves, a belt composed of a plurality of rubberized layers each containing steel cords, and a carcass of a radial or semiradial construction. The tread includes two half regions divided with respect to a crown center, one of which being a region in a direction of plysteer due to the tire construction and the ground contact reaction force acting to steel cords of at least one rubberized layer disposed near the tread and the other being a region opposite to the direction of plysteer. Reinforcements are provided on walls of tread grooves at kicking-out side of the region opposite to the direction of plysteer.

Large-sized pneumatic radial tire

A heavy duty pneumatic radial tire having tread patterns divided into a central zone and peripheral zones by two main continuous zigzag grooves spaced apart a distance 25-38% of the overall width of the tread and having a main groove oblique or zigzag angle of 55-78.degree. relative to a radial plane of the tire. Each of the peripheral zones is divided into the form of arrow feathers by traverse grooves having walls tilted through at least 20% of the depth of the traverse groove at an angle within 20-40.degree. to a center line of the traverse groove. The ratio of total areas of the central zone to those of one of the peripheral zones is 1:1.0 to 1:1.5, and the ratio of the total areas of inner and outer peripheral blocks in the peripheral zones divided by a continuous zigzag groove substantially parallel with the main grooves is 1:1.5 to 1:2.5, thereby greatly mitigating ununiform wear at the shoulders of the tread, heal-and-tow wear between front and rear edges of blocks defined by the grooves in the pattern, and railway wear at the edges of the blocks in opposition to the grooves.

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Higashimurayama, Japan

Shigeta Aoki