nonsensez9 said:I know the 18x8.5 will fit an '05 GT. Thing is, I'm interested in a set of 18x9 wheels that have an offset of 38mm. Not too bad, but I think it will stick out a bit too far for my liking. I was of the impression that the "right" offset for a 9 inch wide rim would be around 50mm.[/QUOTE
nonsensez....let me try to explain this offset thingy to ya.......our stock wheels are 17X8 with a 45mm+ offset. now that + sign is important. the offset is measured from dead center of the wheel. dead center being 0 offset. the stock wheel's mounting position is 45mm+ from dead center which puts most of the wheel under the car. Deep dish rims have a 0 or - (negative) offset rating which means most of the wheel is to the outside of the car. as that + number on our beloved mustangs gets smaller you're moving closer to dead center....which means you're bringing more of the wheel out from under the car. now dead center of the wheel will always be dead center. regardless of how wide the wheel is. going from an 8" to a 9" will add a half inch to each side of the wheel measuring from dead center. so.....going from a 17X8 to a 18X9 with a 45mm+ offset (same as stock) will bring the wheel 1/2 inch out from dead center. if you want your new 9" wide wheel to be exactly where the 8" stock wheel was.....i'd say a 50mm+ offset is pretty darn close. but you've got a couple inches to play with before the wheel will start to stick out past the fender.
i hoped this helps and doesnt confuse the issue more.