The Yokohama Rubber Co., Ltd.

Hiroyuki Kaidoo

Shuji Takahashi

Sadakazu Takei

Takao Muraki

Yasuhiro Ishikawa

Rubber compositions are disclosed which exhibit enhanced dynamic modulus and tensile strength characteristics. A selected type of carbon black, resorcinsol and/or its precondensate and hexamethoxymethyl melamine are combined in specified amounts with a selected class of starting rubbers. The carbon black has specified nitrogen adsorption surface area, dibutyl phthalate adsorptivity and Dst mode of diameter.

Rubber compositions containing carbon blacks of specified physical

Pneumatic radial tires are disclosed which are comprised of two or more belt plies reinforced respectively with an aramid fiber cord and a steel wire cord. Both cords are coated with one and the same rubber composition made up of a selected class of starting rubbers, sulfer, resorcinol and/or its precondensate, hexamethoxymethylmelamine and a selected class of cobalt compounds derived from organic acids. The belt plies excel in water-resistant adhesion and heat resistance and thus have freedom from ply separation, contributing to a radial tire of improved durability.

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Yokohama, Japan

Hiroyuki Kaidoo