Dan the Gear Man® Tech Note 2:
Theoretically, the front bearing retainers are not a "wear" part that will require replacement. However, if the outer bearing cup wears into the inner face of the retainer beyond 0.001-0.002" it will need to be replaced. To check the fit of your retainer, first clean and verify the inside of the steering knuckle is not worn in any way
(if it is, you need a new knuckle). Remove the brake shield. Install a new QU50205
Wheel Bearing Set in the knuckle (do not pack the bearings or use old bearings for this step!). Bolt the retainer to the knuckle and torque the bolts to 30 lb.-ft.. At a point midway between the bolt holes, try to insert a 0.004" feeler gauge between the retainer and knuckle. If you have the 0.004" or greater clearance, life is good and you can move on. Less than 0.004" clearance means you have problems. Either the knuckle and/or retainer are worn!