Even if he has a stand it might still be hard to get in there since he does have a car tire on it. I would suggest just taking off the whole back end off the bike, shouldn't take long, just a hassle. Just take off the rack and rear side panels, and then the rear fender, it's a little tricky but not too hard. Then get the tire in there how you want it and put it back together.
If you don't have a stand you can pick one up for $40 bucks at harbor freight, or look around on craigslist. You could use car jack stand some how, or use a ladder and ratchet straps to keep the bike up, but the stand is really worth it.
If you're really set on putting the bike on it's side use a couple of tires to rest it on at least, I have to admit I am guilty of using the same technique but that was on a $400 and I didn't really care. As for which side is best I have no idea.
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