The way I have done this is to take the wheel and bolt it onto the front hub of the car that you want to use it on. I use a dial indicator on a clamp-on base to measure the run-out on the rim as I rotate it by hand. As long as the hub is running true this will give you a good idea of what condition the rim is in. If you don't have a dial indicator, a piece of wire used as a pointer will at least give you an indication if the wheel is seriously "bad".