My rear novatech track hub was having some grinding issues, so I removed the cartridge bearings to replace them, however only after I removed them did I notice the LBS gave me the wrong-sized cartridges. However, I was playing with the old bearings and they seemed to spin pretty smoothly in my hand. I cleaned out the bearing again and they seemed to spin like new. However when I reinstalled them into the hub, they had the same grinding issues again.

Is it the bearings that are the problem then? or is it the hub? I'm thinking maybe imprecise machining tolerances are maybe putting a lot of stress on the cartridge?

I'm going to try replacing them again tomorrow when I exchange the bearings for the right ones, but I'm worried I may get the same grinding anyways.

Just a note, that the hub were already grinding when I bought these wheels used 4 years ago. I just didn't get around to servicing them until now. The front hub spins smoothly.