PNEUMATIC RADIAL TIRE FOR CAR

This invention relates to a pneumatic radial tire for a passenger car comprising a pair of bead portions and a carcass comprised of at least one carcass ply toroidally extending between a pair of bead cores embedded in the respective bead portions and containing organic fiber cords, characterized in that the organic fiber cord constituting the carcass ply is a polyketone fiber cord satisfying the following equation (I): à ‰¥ - 0.01 ¢ E + 1.2 and à ‰¥ 0.02 [wherein à is a thermal shrinkage stress at 177°C (cN/dtex) and E is an elastic modulus at 25°C under a load of 49N (cN/dtex)] and the polyketone fiber cord has a ply-twisting coefficient N 1 defined by the following equation (II) of 0.35-0.70 and a cable-twisting coefficient N 2 defined by the following equation (III) of 0.50-0.95: N 1 = n 1 × 0.125 × D 1 / Á 1 / 2 × 10 - 3 N 2 = n 2 × 0.125 × D 2 / Á 1 / 2 × 10 - 3 [in the equations (II) and (III), n 1 is a ply twisting number (turns/10 cm), n 2 is a cable twisting number (turns/10 cm), D 1 is dtext of ply-twisted yarn, D 2 is a total dtex, and Á is a specific gravity of the polyketone ocrd (g/cm 3 )].