I'm putting 31x10.5 tires on my 94 F150. Do I have to order a new tire this size for the spare, or can I use the old stock size tire as a spare? Seems to me it wouldn't be much different than using those temporary spares. Hope somebody can help me answer this question.

 

If you have limited slip, I would not use it on the rear. Swap a front tire to the rear if it is a rear flat. If you have 4x4, only on the front and not in 4x4.