Absolute limit on standard height is 8.5j et44 with 235/45/18 tyres. You won't get any rubbing until you go over bumps over 20mph, or take a corner too fast. If you are lower, you want a higher offset, around et48/50.
On that size wheel, I am lead to believe having 225 width tyres will sort it out, but obviously they're then stretched. I'd say 8j et48 would probably be about right. Otherwise you're probably gonna have to get stretched tyres, rolled arches or other mods. However, if anyone can tell me that it can be done another way, do it. I could be way off. Haha :)
