Just got a nail in my tirer!
 

left rear wheel! tirer is about year old with 15k miles on it, since the nail is on the side wall don't think they will be able to fix it! also drove about 1/4 mile with it flat until i was able to pull over(heavy traffic)!
couple questions, what is the max difference between treads? since i have quattro!
if the difference is too big do i buy all 4 new tires?
thanks
Sam

You ALWAYS match treads with four wheel drive. I don't care what AWD system you've got, its trouble
 

brewing if you don't.

do you have a full sized spare?
 

If you have a full sized spare that has brand new tread I would reccomend putting that tire on one side on the rear axle and replacing the flat with the same brand on the other side and putting the right rear wheel/tire in the trunk as a spare.

if you don't have a full sized spare or don't want to use the same brand/tread type I would suggest getting 2 new tires of the same brand and tread pattern of the fronts and replace the two rears but then rotate them up front as to have the full tread up front and the 15k treads on the rear.

you don't need to throw out the 15k mile old rear tire, you can probably pick up a used audi rim pretty cheap and mount it as a full sized spare. Also I would suggest inspecting the 3 tires that are in good shape and choosing to ditch the worst one instead of simply the right rear.

someone is awake - good suggestions

i don't have a full spare! and how can i match treads?
 

can the tires in the front be different(tread size) from the ones in the rear?

I'd say yes - when I bought my car 2nd hand it had two new at the front and ...
 

two half used at the rear. As long as they are above the wear indicators (or minimum recommended depth) you should be fine ...

I like kumho Ecsta has good performance. :)

Its not a problem,
 

15K wear on a tire is nothing. If we were talking 30K or more maybe.

You can order a tire shaved to the tread depth of your current set...

...or buy 2 full-tread. ;0)