I assume you mean the races need to be installed in the hubs, and if so, try warming the hub by whatever means you have handy. I'd put the bearing race in the freezer for an hour or so, put the hub in the oven (while the wife is not home if you value your life) and heat it to (around) 200 degrees and the race will drop right in. Keep a brass drift and a hammer near "just in case" and you won't have any problems. But you do need to wait for the hub to cool before tapping in the seals.