I have replaced all the bearings on my trailer and never needed to have the races pressed in or out. A brass drift and a hammer is all that is needed. I changed mine only because the trailer had a lot of miles on it. The bearings on one wheel only was showing wear but to avoid problems I replaced all bearings, brakes and magnets. Keeping them well lubed, not over lubed is the best way to make the last. Trailer is ten years old and has at least 75,000 miles on it now.
bkick