Rolling bearing unit for vehicle wheel

A rolling-bearing unit for a vehicle wheel comprising:

• a stationary member fixed to a suspension and having an inner peripheral surface formed with an outer ring raceway,
• a rotatable member provided to support the vehicle wheel and having an outer peripheral surface formed with an inner ring raceway and a housing which is to be an outer ring of a constant velocity joint,
• a plurality of rolling members rotatably provided between the outer ring raceway and the inner ring raceway,
• balls provided to be in contact with the housing,
• the housing having an inner peripheral surface formed with a plurality of outer engagement grooves extending at right angles with respect to the circumferential direction,
• the outer engagement grooves having an opening on both of the circumferential sides which is provided with a chamfered portion, and
• the chamfered portion having a radial size which is to be larger than the elastic displacement of the area of contact between the balls and the housing adjacent to each other when the surface pressure at the center of the contact portion of the housing with the balls reaches 4200 MPa.