I've got two sets of 18' wheels with my 09 factory JCW. I'm not crazy about the apparance of the low profile tires, old fashion I guess. Does the 18" offer a performance factor or not. I also want to get a set of all season tires on one set. I may be better off with 17" , if the wheels will clear the JCW brakes.
Thanks
Jerry

 

I have 17" R99 wheels on mine. I don't think the 18s will give you better performance. It will depend more on the tires and wheel weight.

 

Unless You Go With Actual Lightweight Performance Wheels Such As Volk Or Works Or Anything Like That It Wont Give You Any Performance. Most 18s Are On The Heavier Side So Stick With 17's, Lighter, Cheaper Tires, You Can Fit Bigger Meatier Tires And Depending On The Style THey Should Clear The Brembos

 

Beware of potholes with 18" rims. I have already bent two of mine and lost two good tires, they balanced fine though.

 

Much better tire selection with 17s.tirerack has some ssr and volk wheels on sale right now .

 

All else being equal, a 17" wheel will be lighter than an 18".