Carry two spares?
Several years ago I was in some far off spot in Arizona when a very sharp piece of scree cut a large gash in the sidewall of my 31-10.50x15 radial. As luck would have it, I was on a one track road going up the face of a mountain to check out a mine. Since the road was so narrow, I had to proceed about 1/4 mile to find a relatively level spot so as to put on my spare. I still had about another mile of scree covered switchbacks to go before reaching the mine. All the way back down I was very apprehensive about making it out without any more problems which, fortunately, I didn't run into. Ever since then, I've been a firm believer in carrying two spares. I suppose that if you go out in a group and another member of that group has a compatable spare you would probably be OK. Me, I often go out as a single vehicle and I now drive a Pinzgauer so trying to find a compatable spare could be difficult.
Cheers, Stevo