Will 235/40 by 18x8.5 fronts and 265/35 by 18x9.5 rear fit on my GTO without rubbing? Will they fit without having to modify any fenders? Also will this solve the problem of my front tires rubbing on the struts? Will the 3rd AvP movie rock as hard as the first two?
Thanks for your help.

Search for the thread titled "18 inch wheels???". This will be very helpful to you.

no, they will not fit with out modifying things

If the offset is less than +48, they will increase the distance from the tire to strut

Les Schwab says that a pair of 18x8.5 in the front with 235/40's and 18x9.5 275/35's in the rear will fit just fine. I called Tirerack and the dude told me that they will fit on the front fine but that Pontiac recommends at least a 61mm offset in the rear and the rims I want only go as far as 45mm offset so he can't guarantee fitment. The rims I'm looking into are the Beyern 5's, if anyone has them on there car I would like to hear how it all went down, thank you.

I can't say from experience, but I would think that for the rear a 9.5 inch width rim with a 275 series tire is probably going to either rub on the inside wheel tub or outside fender lip depending on the offset of the wheel. I suppose a spacer could bring the wheel out from the inner tub but then you may have to cut/grind the lip of the fender so it doesn't rub. Pontiac/Holden really made it hard for us to get wider rubber under this car. :( Good luck. :)

Ok nix the new rims idea...I am I crazy or have I seen people putting a 275 series tire on the stock 17in. rims?

am I crazy or have I seen people putting a 275 series tire on the stock 17in. rims?

Yep some are doing it. Widest I'd go on the stock 17 inch rim in the rear would be 255. Unless someone has drag springs and drag bags.

Yeah I guess I'll let the rims alone for now but they are going to get some new rubber regardless...thanks again fellas.