balls to some extent and therefore the variation in the curvature radius from the groove bottom to the groove edge may be smaller than that in the inner race now assuming f 1 f 2 gt 1 3 the riding of the balls onto the orbit groove shoulder of the outer race will be prevented but the contact surface pressure in the neighborhood of the shoulder will become great and flaking will occur also assuming f 1 f 2 lt 1 10 the contact surface pressure in the neighborhood of the shoulder will become small and flaking will be prevented but the riding of the balls will become liable to occur it is therefore desirable that the coefficient of the orbit groove of the outer race 1 satisfy the following condition equ3 description will now be made of the result of the comparative experiment carried out for the embodiments of the present invention and the prior art bearing tested as the wheel bearing of the semi float type rear axle of an automotive vehicle table 1__________________________________________________________________________no 1 outer race str1 str2 f sub 1 6 074 str3 inner race str4 str5 f sub 2 18 742no 2 outer race str6 str7 f sub 1 4 780 str8 inner race str9 str10 f sub 2 18 742no 3 outer.