Shouldn't be a problem. 275/35/18 is the size Turner motorsports runs on all fours at the track on their E90 M3. They use 18x10 Forgeline wheels but an 18x9.5 width should work just fine too with that size tire. It makes for an ideal square set if you want to go that route.
I'm planning on going with four 18x9.5 Volk TE37s for a square set for the track. The great thing about that size is that there are many tire options. 275/35/18 gives you the choice of BFG-R1, Hoosiers, Nitto NT01, Toyo R888 or RA1, to name a few good ones.
2008 ///M3 Coupe, AW/FR ext, M-DCT (gone)