My car is an '01 2.7t 6spd. My car has the standard 16" OEM wheels and stock fitment of 215/55.

I am considering 17" or 18" wheels. Will 18" wheels/tires fit inside wheel wells? What would be the correct fitment for the 18" option? The 17" option?

235/40 x 18 tires. I've run 245/40 x 18s and had a little rubbing issues but removal of the top fender-liner screw solved that. Friends with 18" x 8.5" et30 wheels had more pronounced rubbing issues during very aggressive (track) driving. His car had the factory A6 2.7T sports suspension, and I have H&R coil-overs set lower than the sport suspension. The 8.5" et30 wheels fit better on the 4.2/S6 with their flared fenders.

For 17" wheels I use S6 Avus...17" x 8" et35 with 235/45 x 17 tires. I use these wheels now for my winter tires (225/50 x 17) which produces about a 2.7% odometer/speedometer error.

HTH