BEARING DEVICE FOR WHEEL

An object of the present invention is to provide a wheel bearing apparatus which can reduce the torque applied to the splined portion of the hub wheel and thus can improve the durability of the hub wheel. According to the present invention there is provided a wheel bearing apparatus comprising an outer member integrally formed on its outer circumference with a body mounting flange adapted to be mounted on a knuckle of a suspension apparatus and on its inner circumference with double row outer raceway surfaces; an inner member including a hub wheel and at least one inner rings, the hub wheel being integrally formed on its one end with a wheel mounting flange and with a cylindrical portion axially extending from the wheel mounting flange, the inner rings being press-fitted onto the cylindrical portion of the hub wheel via a predetermined interference and formed on their outer circumferences with inner raceway surfaces corresponding to the outer raceway surfaces of the outer member; and double row rolling elements freely rollably contained between the inner and outer raceway surfaces of the inner and outer members via cages characterized in that a hardened ring-shaped gear member is mounted on an end of the cylindrical portion of the hub wheel, the gear member being formed on its outer circumference with a gear portion and on its inner circumference with a splined portion engaging a hub-splined portion formed on the outer circumference of the cylindrical portion of the hub wheel; that both a contacting surface of the gear member and a contacting surface of the inner ring being abutted against each other are ground; and that the inner rings are axially immovably secured under a condition in which a predetermined amount of a bearing pre-stress is applied to the inner rings via the gear member.