Anyone know wheel size and backspacing of a GNX?

Bruce Urie

The Ventures,CCR forever!
In the near future I'm wanting to get a set of Torque Thrust IIs for my '87 Grand National....but I want the wheels to be 16x8 like the GNX, but I don't know of the backspacing of them. I want to put the same size on all four corners. I think the tires are P245/50-16. Is this right? (The tire size)

Sure would like to know the backspacing for all four wheels to make sure they'll fit without sticking out of the fenderwell.

Sure could use this information. Thanks kindly.

Bruce '87 Grand National


Active Member
From what I've read
245/50/16 front
255/50/16 rear
-15 front
-23 rear
The offsets were stated in metric so I don't know what that translates to in English.
Hope this helps.

Bruce Urie

The Ventures,CCR forever!
Yes, Scott, you helped me alright. The front offset is what I needed, at -15.....I can get a wheel with a -12 offset that I think will fit. Opinions on this option would help me, please. Once I buy the American Racing Torque Thrust IIs, they have to fit, as I can't return them.

BUT: If anyone can help, I need the BACKSPACING of the GNX front wheel: the distance from the inside mounting surface of the wheel to the outside rim.....if anyone knows this, I would be very grateful. I'll even tell a good story, too, to throw in my appreciation.

I know Dennis Kirban would know as he sold these wheels at one time......

Thanks, kindly, Scott.

Bruce '87 Grand National

Anthony P

sharing knowledge with those who care to listen
Bruce, give me a few minutes. i saved all this data from an old thread. don't remember what forum I was using at the time. I'll post a screen shot. archives are on a different computer.

Anthony P

sharing knowledge with those who care to listen
it was a thread that began Nov 4, 2006 titled "Info on GTA wheels" by justabuickv6. maybe the thread is still available via search. you can see by the screenshot below it is the old layout of this forum.

GNX wheel specs.JPG

Bruce Urie

The Ventures,CCR forever!
Anthony, that's exactly what I've been looking for....the backspacing and offset. Can't thank you enough.

And also to Scott, thanks a million. Great help for me.

Bruce '87 Grand National

Dennis Kirban

Well-Known Member
kirban 2 cents worth

I went thru this nite mare when we had our kirban style GNX wheels made around buddy at the time ran the chrome shop for american racing he bough the tooling from them as they never made the wheel for the G body application. I ha dno idea what would work so I had him make a half dozen 16 by 8 wheels with various offsets. I then went to a tire place told them to mount and dismount tires on these wheels to determine what it takes to make it fit under the fenders.

what is confusing is offsets back side setting plus the fact a 8 inch wheel is really 9 inches wide 8 inches is whee the tire seats. again I was a dummy at this/

key is having good springs up front even with the perfect height tires can rub inner plastic fender ever so slightly if you turn the wheels real hard and going up a slight slant on a driveway plus ad the fact none of our cars are sitting exactly straight on the frame....

I thin kits like zero zero offset or whatever fronts are on a firebird or the number you seek.

good luck

worse case you can always use a thin spacer....without getting longer wheel some cases.

again I am not an expert merely stating what we did. My same supplier made the very first pontiac ralley Is reproduction and Mopar reproductions we did the ralley Is in 15s even though Pontiac never offered them...

the real high dollar wheels we messed with back in the day was the Hurst wheels they would bring $2500 to $3500 a set used....this was over 20 years ago.....

Bruce Urie

The Ventures,CCR forever!
Good to know, Dennis. Thanks. So, what I surmise here is I should get a 16 x 8 wheel with ZERO offset and a 4 .75 inch backspace. This is the backspacing for the front GTA I could use this specification for all four wheels on my Grand thing I must avoid is the tires sticking out or the wheel sticking too far out or too close to the suspension.

So we agree with these specs? 16 x 8, ZERO offset, 4.75 backspace. Right?

I sure appreciate your 2 cents worth, Dennis....and thanks to the others that chimed in to help me.

I'm horribly old school....loved American Racing Torque Thrust IIs since I was a little squirt..most of my models had them on, though they were the old style American Racing Torque Thrusts with the gray spokes that had a ridge on each spoke.... .....though, I must admit, on my brand new '68 Pontiac Firebird 400 with Ram Air, I put 15 x 10 Ansen Sprints on the back and 14 x 7 Ansen Sprints on the front...painted each slot in the wheels with Craiger mag wheel dark gray paint..........for street and drag, that "Bird" looked nasty! Sat up pretty high....road like a truck, rough, firm, had Lakewood traction bars on it......Loved those Ansen Sprints.....remember those? You should, you're the same ancient age as me! :p

Bruce '87 Grand National

Anthony P

sharing knowledge with those who care to listen

when folks were hunting down GTA wheels for the GNX look, the desired result was to get 4 fronts. That ensured the wheel would look right in the opening and there would not be the need to trim the fender lip, cut and patch the rear section of the plastic wheel well, and add fender flares like the GNX.

When Classic Industries brought back a reproduction GTA wheel, they initially would not sell a set of four fronts - part # 10104410. But they came around when they got a boat-load of requests. Check out their page...

the wheels have been out of stock for some time but the product page shows stock is arriving soon.

note that classic also offers a 16 x 8 wheel with 5 in backspacing and 16mm offset - a slight change from the specs for original REAR GTA wheels