Had a front left flat tire on my A4 Quattro yesterday. Unfortionatly it wasn't the tire and was a hairline crack in the wheel that had grown larger It is an RS6 type wheel 17" with 225/45R-17 tires. Instead of putting the small spare back on, I installed my original wheels and tires just on the front left and right which are 295/65R-15's. Because I'm all wheel drive, just wondering if I'll be okay to run this way until I can get a new wheel?

 

From what I understand about the quattro system, it is not good to have any discrepancy in wheel size and yours would be a pretty big one. Don't drive it like that for very long.

(I just posted a similar question and my discrepancy would only be 1/4 of an inch)

 

^he is correct.

 

Anything more than about 3% of the rolling diameter of the tire will eat up the center diff. For example, the diameter of a *new* set of 225/45 17's is 24.972". 3% of that is about 3/4". So depending on the amount of wear you have on either set, you could be in trouble. If you have no choice but to drive like that for a day or two I don't think your car will blow up and the wheels will fly off, but I wouldn't press your luck any more than that...

EDIT: Sorry, I just re-read that post and realized that it was kind of cryptic and not finished. So the point of all that math was that if the diameter of any of your tires is more than 3/4" +/- any of the others, it will cause excess wear on the center diff.

 

Chris your reason for editing. Hahahaha.

Audi doesn't recommend even using different tread patterns, so don't do it for long.