I just purchased 18" Sahara rims and now I'm having 255/70/18 toyo A/T 2's mounted now the spare will not be the same size as these because I do not want to mod the hitch and frame to fit the bigger tire... If I ever do have a flat would it cause lots of problems if I were to throw the 17" 265/65/17 spare I have on? I would get it to the closest gas station or tire shop..
Hopefully someone who has actually tried doing this can add their experience.
In theory, I would say that is a bad idea. The difference in rpm for that smaller tire is likely going to keep activating the traction control system and put a lot of stress on the drive train - even if it is for just a couple of miles.