Or should I take the Z4 that has the stock Bridgestone Runflats?
I think they come with these?
Potenza RE050A. Should be the same as the 335i tires...
http://www.tirerack.com/tires/tires....Potenza+RE050A
Wet traction is only 7.5
RS3s have a 7.0
http://www.tirerack.com/tires/tires....tnum=25WR6Z222