PURPOSE: To make it impossible to charge air to the tire which is wrongly secured by specifying the external diameter of the collapsed angle portions of a drop center and by forming the air hole which extends from a well side wall to a bead seat side at the inside of the collapsed angle sections.

CONSTITUTION: On both sides of a drop center section 6, bead seat sections 3 and rim flanges are continuously arranged respectively. In such wheel rim, the external diameters T1 of both collapse angle sections 4 on the width side of the drop center 6 are formed smaller by specified quantity (x) than the external diameters T2 of the roots 2a of the rim flange 2. At the collapsed angle sections 4, the rising wall surface of the drop center 6, i.e., the air hole 4a which extends a wellside wall 5 to the side of the bead seat 3, is formed so as to be positioned at a position on the inside more than the external diameter T1. In addition, the air hole 4a can be formed easily by carving grooves 7 at several limited part of the rim in the peripheral direction of the collapsed angle section 4.