I wnet with 18x9 and 5mm spacers in the rear. I think 10 mm is closer to ideal but tire rack did not have them for the M3,
I HATE changing tires and the track and taking them in my backseat. I prefer to do it in the comfort of my own garage. T Rcomp tires are ok in the rain if you are sensible. of course it never rains in Sunny SO Cal.