We get this question a lot, and we're fully prepared to answer it. Whatever Audi you drive, Tire Rack has distribution centers across the U.S. full of options. Search for your Audi tires by size, or shop by vehicle. You'll find some great tire insight, like the consumer reviews given below, which reference Original Equipment Size 225/50-17 tires available for the Audi TT 2.0T Quattro Roadster.
"The difference is amazing. The ride is much better and quieter. Steering response is excellent. It is like I just upgraded the suspension system on the car." Continental ContiSport Contact 2 SSR
"Excellent tires. I floor it and there's very little tire spin now, even with lots of performance parts on the engine. Wet traction is superb." Bridgestone Potenza RE760 Sport