motoman159,
I had 245/40/18's on my 18x9.5+15's in front before..It was too much trouble with fitment and the 255/35/18's fit much better then the 245/40's do. and if the 245/40's are clearing your coilovers right now the 255/35's will deff clear. and as far as brakes goes...
My RPF1's clear the 370Z Akebono front brakes with ease(about 15mm gap from spokes to caliper). Good luck finding 3pc wheels that'll clear BBK in 18". one of the reason why I just stayed RPF1's.