Preload inspection method and assembly method for bearing device for vehicle wheel

A preload inspection method for a bearing device for a vehicle wheel including:

• an outer member having two rows of outer raceway surfaces on an inner periphery;
• an inner member including a hub ring that has a small-diameter step portion extending in an axial direction on an outer periphery and an inner ring that is press-fitted into the small-diameter step portion of the hub ring, the inner member having two rows of inner raceway surfaces facing the two rows of outer raceway surfaces;
• and
• a plurality of rows of rolling bodies rollably accommodated between both the outer raceway surfaces of the outer member and the inner raceway surfaces of the inner member, the preload inspection method comprising:
• a press-fitting step of press-fitting the inner ring into the small-diameter step portion of the hub ring to a position where the inner ring abuts on the hub ring in the axial direction;
• a first bearing preload value calculation step of calculating a first bearing preload value of the bearing device for the vehicle wheel based on a first axial negative gap between the inner ring and the hub ring after the press-fitting step;
• a first rotational torque measurement step of measuring a first rotational torque of the bearing device for the vehicle wheel when the inner member and the outer member are relatively rotated after the press-fitting step;
• a caulking step of caulking an inner-side end portion of the small-diameter step portion to the inner ring after the first rotational torque measurement step;
• a second bearing preload value calculation step of calculating a second bearing preload value of the bearing device for the vehicle wheel based on a second axial negative gap between the inner ring and the hub ring after the caulking step;
• a second rotational torque measurement step of measuring a second rotational torque of the bearing device for the vehicle wheel when the inner member and the outer member are relatively rotated after the caulking step;
• a third bearing preload value calculation step of calculating a third bearing preload value by adding, to the first bearing preload value, a preload change amount after the press-fitting step and after the caulking step, the preload change amount being obtained based on a differential torque between the first rotational torque and the second rotational torque;
• and
• a determination step of determining appropriateness/inappropriateness of a preload applied to the bearing device for the vehicle wheel depending on whether or not a difference between the second bearing preload value and the third bearing preload value is equal to or less than a predetermined threshold.