How important is a same size spare tire?

[skibama]

Okay, so I know it recommended to have the spare tire the same size as the other tires, but how important is it really? I mean if I get a flat and have a smaller spare than the other tires, will I be able to drive on it at all, or will the traction control and all other devices make it unusable? I'm just curious to the actual unuseablility (is that a word?) of a smaller spare.
Thanks.

 

[Will816]

Okay, so I know it recommended to have the spare tire the same size as the other tires, but how important is it really? I mean if I get a flat and have a smaller spare than the other tires, will I be able to drive on it at all, or will the traction control and all other devices make it unusable? I'm just curious to the actual unuseablility (is that a word?) of a smaller spare.
Thanks.

How much smaller? If you're running 265/70 and your spare is a 265/65, you're probably just fine. Substantially smaller and the TRAC may drag on the brakes to try and get the axle halfs to rotate at the same speed

 

[skibama]

Yeah, that's my setup now, but i'm debating (really driving myself crazy) whether or not to go with a 285/70/17. I guess I can always use one of my 265/70/17's that I have on now as a spare if one size down won't really make a difference.

 

[Kmvreter]

... if one size down won't really make a difference.

One size difference works just fine. I've run my spare 265/70 (Doneflop) for several days with all the other 265/75 (CT) and 275/70 (BFG.)