[694.1]

Your post is extraordinarily valuable.
Thanks.

[Sirrotica]

Originally Posted by transam greg

I have been following this thread because I also have new rotors
and new (made in USA) Timken bearings with races.
I was thinking the same thing, should I remove the races in new
rotors and install the new races and bearings or just the new bearings.
So after a good cleaning, masking then painting of the new rotors
I say what the hell replace the races. Well apparently the (made in China) races I knocked out were installed without cleaning
the rotor after machining. I found iron powder and machine chips
behind all of the races. Now I don’t know if the rotors were made
in China but most likely yes. I bought them from Summit. I cleaned out the seats of the rotors for the new races and pressed them in. Just thought I’d share my encounters with rotors and races.

The races are in the new rotor so that they can be cut on a lathe, the races must be installed before the face of the rotor is machined, they're the concentric centering point that the face is machined off of. As a mechanic that has cut plenty of rotors/drums, any time you machine a rotor on a lathe your going to get metal inside of the hub area. After the machining operation you wash all the old grease and metal filings from the hub with solvent and a brush and blow it out with air, problem solved.

Any rotor I was installing would be washed and then blown out, new or used. Removing the races isn't necessary at all. As a matter of fact your risking having the rotor with more run out than leaving the race in place that the rotor was originally machined with. If you machine a rotor and unclamp it in the lathe, then clamp it again with the same races, it will never run true the second time it's clamped, it will always have run out. IMO there is no need to replace the races with the ones that came with the bearing, or remove them for cleaning out the machining residue.

It's pretty much the same as cleaning a block that just came back from the machine shop, I'm not going to assemble an engine hoping the guy at the machine shop did a first class cleaning of machining residue.

BTW, it was never implied that the hub and races it was machined with shouldn't be cleaned before assembly. Just that there is no need to remove the original races, and substitute the new races with new races before assembling the bearings. The OP asked if it was better, or necessary, never had problem one leaving the races in that the rotor was machined with. If it makes anyone feel fuzzy replacing new races with new races, then by all means do it.