Gary_44

I once fried the locking rearend on my Int'l Scout by driving it with a slightly smaller spare tire for too far. Afterwards I did a big head slap. Of course, one tire is spinning faster. Doh!
I noticed my Mustang GT has a tiny donut spare. And LSD. Am I missing something?

Mr Nice Guy

I believe you are only supposed to put it on the front and put the good front on the rear. If you run the spare at a slow speed for a very short distance it might be ok. I would check the manual to find out for sure.

Gary_44

My owners manual just has the usual donut precautions, like don't tow a trailer or drive through a car wash, which is pretty funny that they had to put those in there because it means somebody actually once did it.
But, nothing about the rear axle. I think I'll be safe and only put it on the front anyway.

Mr Nice Guy

Any idea what the difference in diameter is? I haven't measured mine.

school boy

Factory spares are 125/90/r15, which according is about 25.1 tall. The factory tires are about 25.4 tall. The difference is minimum and you should be ok.

LilRoush

Yeah, factory spare is close to stock size wheel.

It's fairly general knowledge to not put the spare on your drive wheels - either rear on RWD or front of FWD.

I carry a full size spare rim/tire instead of the tiny stock one.

Z28KLR

Speaking from experience, you can run the donut on the rear for a little while without any damage to the diff. The handling characteristics of having on the rear though, uggghhh, even worse than mounting it up front.

I'm guessing your Scout had a locking rear as opposed to limited slip, which is why it was damaged. With a limited slip differential it allows each axle to turn at a different rate without binding. A locker won't.