What's the real scoop re. mixing tire sizes on Quattros?

[erict1957]

I've read on otehr forums that mixing tire size on a Quattro is permissible as long as the difference in diameter, circumference and rotations per mile is 3% or less. Does Audi support this tolerance or does any similar tolerance exist? THANKS!

[HOFFY11]

I've read on otehr forums that mixing tire size on a Quattro is permissible as long as the difference in diameter, circumference and rotations per mile is 3% or less. Does Audi support this tolerance or does any similar tolerance exist? THANKS!

you need to have the same diameter/ ride height all around ..i really dont know why but i know its true lol..a tire company will figure it all out for you

[R1CH-5100]

I was wondering the same thing. I just got a flat and am running a spare that doesn't match. Obviously I'm getting it patched asap but how much damage is going on if any?

[Doc@tirerack]

Mixing different diameters wil hurt the differentials more on a long term basis, so 50 or so miles on the spare won't do much harm.