You unbolt the tire on the ground, then jack it up and remove the tire.
wtf?
What do you mean, "wtf?" That's how you are supposed to do it, so the tires won't spin as you break the bolt loose, dude.
Actually if you do that you might break the bolt due to the pressure of the car on the bolt.... your suppose to Jack the car up then unbolt. (and don't try to question me cause I am a Mechanic). Ask Dan (who has BUILT his car) how you are suppose to do it if your unsure.
I didn't mean completey remove the nuts, I meant break loose. Then you jack the car up, and remove them all the way, replace tire, tighten bolts as far as you can, then put it on the ground and torque on them.
[Edit]
Any how, if the four, or five, or how ever many bolts (depending on the axels) can support the car with the nuts, the bolts should support the car with out it. It might have the chance to mess with the threads, but that's quite unlikely.