A 245 on an 8 is flush and a 255 on a 9 is too. 255/40/18's on 18x9's is what Peter runs on his with staggered wheels. He can answer your question to a t.
O, you know what, I'm forgetting that the wheel width is measured from the inside of the lip on one side to the inside lip of the other side. The lip extends an extra inch on each side. Stupid error on my part. :violent1: