I have been reading and reading and reading.

I have run searches.

I have NOT gotten a clear answer yet.

I have a 96 Firebird Formula, on stock suspension. READ: NOT LOWERED.

I am going to get 17x9.5 & 17x11" ZR1 replicas. I also plan to run 315/35-17 tires in the rear.

I can get either the 50mm Grad Sport offset or the 36mm ZR1 offset.

I would like to know what offset you have, and what modifications you had to make to the car to get the rears to fit without rubbing.

I need to know if you had to roll the fenders, cut the jounce bumper, beat the inner fender wells.

I'd prefer as much Firebird/Trans Am owners input as I can get since it will directly apply to my car. I understand there is a difference in the rear fenders vs the Camaros.

Thanks all, and please bear with me on this...

 

You need 17x11 50mm offset in the back, 17x9.5" 56mm offset in the front.

POSSIBLE MOD'S REQUIRED [Varies extremely from car to car]

-Cut the corners off the jounce bumper bracket.here

-Hammer the inner fendershere

-recenter the body over the axle with an adjustable panhard roddrivers side
passenger side


I would say everybody has to (or should) do the jounce bumper bracket, what you have to do after that depends on the specifics of your car, and it varies all over the place. I did all 3 of the above, and I can post pictures. You might remotely have to roll the lip on the fender a little, but I only saw contact on that area on extremely hard shifts, and recentering it with the panhard rod eliminated it.

But you should have been able to find all of this with a search.... I know I have posted this info multiple times on this forum.

End results -1

End results - 2

 

Fred, thanks for the reply!

I did see where you'd posted on numerous occasions that you had the GS offsets.

I have also seen others that have the ZR1 oftsets, 36.5mm rears and 38mm fronts, and seem to say that fewer mods are required.

I did not see in any of the posts, any of the work that a Firebird or Trans Am owner went through to get the ZR1 offsets to work on their car.

I also did not find the in depth information that you just provided in your post about the mods you had to make to get the GS offsets to fit.

So, I thank you for filling in the gaps on the GS offsets!

 

Not to belabor the issue... but I'm sure there was an extremely long thread comparing the 36mm to 50mm offsets, specifically on Pontiacs. There were photos of both setups linked. I also have a fairly extensive post that summarizes the recommended offsets (at least my version) for many size wheels on the F-Body - including drag wheels, and compares actual photos of 17x9.5's with 45mm, 49mm and 56mm offsets. And the TT II 17x11's with 7.75" backspace.