PURPOSE: To improve thermal and dynamic fatigue resistance and a life-span by arranging a first and a second reinforcing layers with a specific terminal height outside a carcass which is folded back on a bead, while forming the constitution by means of Apex rubber whose section is a triangle arranged on the upper portion of a bead core.

CONSTITUTION: A first reinforcing layer 2 is arranged in such a way that heights h2 and h2' of inner and external ends 2a and 2b of the first reinforcing layer 2 are respectively lower than the height h1 in a radius direction from a bead base reference line of a folded back terminal portion of a carcass ply 1. And a second reinforcing layer 3 comprising rubber coating fiber cord is arranged in more than two layers outside the first reinforcing layer 2, and heights h3 and h3' of its inner and external ends 3a and 3b are arranged 1.2W1.5h1, respectively. And Apex rubber SE whose thickness decreases gradually in the direction of a tire radius and whose section is a triangle and which is ring-shaped in a circumferential direction is arranged on the upper end of a bead core 13. Thus, thermal and dynamic fatigue resistance and its life-span can be improved.