fast. When I first finished my TT swap I had the NA rear wheels with brand new Bridgestone Potenza RE-750's and I would lose traction getting into boost in third gear. It is not fun having the ass end get squirelly at 80mph. Guess this doesn't really answer your question though. My car is making around 380+whp when it was losing traction, but my wheels were 7.5 instead of 8.5. A friend around here has about the same power output as me. And loses traction consistently in 2nd gear even with 18inch 5zigen wheels with new falken tires. Keep in mind both our cars have NA rear ends also.