255/40R18 would work all around, but the popular 235/40R18 and 255/40R18 is no longer possible, because the 235/40R18 is sold out. They sold out very early, because there were not a lot left over.
I have accepted a new position at Tire Rack and am no longer in the sales department. firstname.lastname@example.org
is available to assist with M3 questions.