I've been searching around the board to find info on the stock wheel dimensions.

I've seen ads on ebay and elsewhere regarding wheel packages that are Corvette Grand Sport or ZR1 offsets, etc. Do these wheels fit directly on our car? I'm wanting a set of SS/ZR1 style (or Z06 style - drool) wheels for a decent price, but I want them to fit w/no mods to the car.

Can someone tell me the stock offset/backspacing/bolt pattern (5x4.75", I think) for the LT1 cars?

Has anyone ever put "Grand Sport" or ZR1 (or, indeed, C5) wheels on his/her car? Not just ZR1 look-alikes, but actual ZR1 (front) wheels? (Not looking for a 17x11 w/315 section rear, at least not yet) Any help is mucho appreciated.

 

The stock wheels are:

16x8 55mm offset = approx 6-5/8" BS
17x9 55mm offset = approx 7-1/8" BS

All 4th Gens, C4's and C5's are 5 lugs on a 4.75" bolt circle.

For 17x9.5" wheels, you need an offset in the range of 40mm (very close to being outside the fender) to 56mm (very close to hitting the steering knuckle. I have seen some Enkei's that are 38mm, and too close to the outside of the fender for my taste. I believe the Torque Thrust II's are 45mm. I have run OZ Monte Carlos at 49mm and AFS ZR1 replicas at 56mm. I can post links to pics of the 45, 49 and 56mm offsets on a Firebird.

You have to be very careful with some of the C5 wheels, since they have a 65mm offset, and can cause problems with rubbing if you don't use spacers. I can give you a table of C5 wheel widths and offsets by model and by OEM vs. aftermarket, out of an issue of VETTE magazine.

 

Thanks, Injuneer! That was most helpful (raw numbers and real world application info). And yes, if you have that Vette stuff in electronic format, you could post it as a link or just email it to me. Links to the different offsets on the Firebird would be excellent.

Thanks again.
Joe

 

I'll have to type in the VETTE stuff when I get home and post it here.

As far as the pictures of different offsets, the pic links are in this thread in one of my posts:

http://web.camaross.com/forums/showt...threadid=74773

 

No need to type stuff in. I mean, if it's just a couple of table entries or something, that's cool, but don't be spending a whole bunch of time! I'm still in the exploratory phase, though there is a guy with some stock '99 Camaro SS rims for sale in Classifieds section. Those might be the easy way to go... Thanks for the links, too.

BTW, I'm not getting the same numbers for stock backspacing using the offsets you gave.

On an 8" wheel, the width is 203.2 mm. Using the formula:

B.S = 1/2*W + O.S.

I get B.S. = 156.6 mm, or 6.165 " for 8" wheel.
I get B.S. = 169.3 mm, or 6.665 " for 9" wheel.

Am I missing something? Both offset and backspacing are measured from the mounting plane (to either the wheel centerline or the back of the wheel, respectively). So I think my equation is correct (and I found the same equation on some wheel sites after I derived it). Why are our numbers different?

Also BTW, that firebird looks bad@ss, with either set of wheels!

 

The "width" of the wheel is stated as the width between the flanges that retain the tire bead. If you meausre the OVERALL width of an 8" wide wheel, it is closer to 9".

That means, that to get the backspace, you have to add 1/2 the wheel width (gets you to the inside of the flange) + offset + the flange width.

So....

8/2 + 55/25.4 + 0.45 = 4 + 2.17 + 0.45 = 6.62" or approx 6-5/8

9/2 + 55/25.4 + 0.45 = 4.5 + 2.17 + 0.45 = 7.12" or approx 7-1/8"

The width of the flange is an assumption, but they usually run 0.45 to 0.50"

Thanks for the feedback on the 'bird. Actually, the Formula just got a new set of even wider slicks.... click on the "Trailer Queen" link below.