The old school method was to always replace bearings in matched sets of inner and outer parts. There wasn't anything like ISO9000 quality/strictly held tolerances back then. Today a lot of new rotors come with races pre installed.
I still replace entire bearing as boxed, matched pieces. Heck even when I pull rotors for turning I sort and mark so rotor and bearings goes back on the spindle they came off of.
The old race removed serves as a driver to install the new race too if that tip helps.
