PURPOSE: To obtain a high-performance pneumatic radial tire by providing any one of twisted cord carcass made of heat contraction type organic fiber, which has a special value coefficient of twisting expressed with a special formula, a bead supporter made of hard rubber and a bead-tow reinforcing rubber stock in a radial tire, which is provided with a recessed part near each shoulder part and which has a circular carcass line.
CONSTITUTION: A recessed part 32 is provided on the surface of a tire near each shoulder part 27 along the circumferential direction of a tire, and both ends of the inside and outside thereof in the radial direction and a carcass line corresponding to it are formed into a circular, of which center of curvature is set inside of the tire. Carcass plies 16, 18 are formed by twisting heat contraction type organic fiber to form cord fabric, and thereafter, coating with rubber, and coefficient of twisting of cords expressed with a formula is set at 0.1-0.5. In the formula, N means number of twisting per 10cm of fiber length, D means total denier, and δ means specific gravity. A bead supporter 38 is formed by attaching a long size crude rubber, which has a nearly triangle cross section, at the time of forming a green tire, and arranging a bead-tow reinforcing rubber stock on both sides of the carcass plies 16, 18.
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OKUMURA FUMIHIDE
HAMAMURA KAZUYUKI
