I've just put winter wheels (17" S spokes with Vred Wintrac's) onto the wifes Cooper S and I'm trying to decide what to do with her summer wheels.
They are the optional JCW wheels that you're meant to use 205/40/18 tyres on but I've had a look and the tyres available are complete garbage. With our old R56 factory JCW I put on 215/35/18 Yoko Parada's which were downright dangerous in the wet.
The most noticable difference is how much the ride quality has increased on the 17's.
What are you all running on the JCW wheels? At a guess most of you will have went to 215/35?