I replaced and repacked the bearing in my trailer this weekend. Everything went smoothly enough, no problems. Only thing is, I could not get the original races out of the hub to replace them, so I left them and just put in the new bearings (after packing them with grease) and greased up the whole works. How important is it to replace the old/original races when replacing the bearings? The originals seemed fine: no grooving or noticeable wear. I would have liked to replace them since I was replacing the bearings, but they just would not budge.