i have 18x9.5et22 265/35/18 RS3
-2.5 camber up front
I have room, I can even do a full lock turn... but I have very very little room. very little.
I want to measure it but don't know how..
but I also have an e93, which, from my personal experiences, has less clearance than e90/e92
People say I'm crazy, but I've done quite a few different wheel/tire combos on my e93 M3 and my previous e93 335... e93s have less clearance.
So you should be fine with a 265/35/18.
What are your alignment specs up front?