ok so i got a flat tire the other day im currently running a 255/70R16 tire but my spare is the stock 255/55R16...will it hurt any thing if i drive on it for a few days till my new tires come in. cuz i know with certin AWD cars having off size tires can destroy your center diff...

 

What are you driving?
You should be fine.

 

You should be fine. The potential problem is when one wheel on a full-time AWD drivetrain has a slightly different circumference and turns more or less times per mile than the other wheels. This puts extra wear on the clutches/viscous couplings/AWD, generates more heat and shortens drivetrain life. I think the AWD GMC Acadias recommend all tires being within a couple 32nds and shaving the tires down if they're not.

But it all depends on the drivetrain and how the system operates. So again the most important question is what are you driving?