I'm looking to get new alloys for my ap1 18 inch on the rear with tyre width of 265. Could someone let me know if this would look too wide on the car thanks

 

Simple question, simple answer. No it would not look too wide, I've some people here run 285 up to 315 in the back, but for sporty purposes also. The width of the tire is not your only issue, you'll have to consider wheel width, offset, fender modification, ride height and don't forget the front as well. If you don't want any fender mods, you're gonna have to run a pretty high offset (60 and up).