Patent ID: 7503699

Claim:
A wheel axle bearing unit, comprising: a flange on an outer circumferential surface thereof, via which to be mounted to a vehicle body; an outer member provided with dual outer raceways along an inner circumferential surface thereof; an inner member provided with at least one inner raceway on an outer circumferential surface thereof; rolling elements rollably disposed between said inner and outer raceways; an inner race having an inner raceway and fixed to an outer circumferential surface of the inner member by a radially deformed cylindrical portion formed at an inner end portion of the inner member, the at least one inner raceway of the inner member and the inner raceway of the inner race being positioned, respectively, so as to correspond to said dual outer raceways of the outer member, and a pair of retainers each of which retains said rolling elements; wherein a first grooved portion is formed by removing an excess in thickness on an outer circumferential surface of said inner member between said dual raceways, for enlarging a space inside the bearing, and wherein a boundary surface between the inner member and the inner race terminates in a space that is between the at least one inner raceway of the inner member and the inner raceway of the inner race and remote from the first grooved portion.