We will use an '82-92 Camaro as the example.
Offset
Backspacing
It can also be calculated, as shown below. Don't forget to add for the rim's lip and tire bulging past the rim (I use about .25"). Our 16x8" 0mm offset front rims would have 4.25" of backspacing. The positive 16mm rear rims (16mm/25.4 = 0.63") have about 4.9" of backspacing
 |
Rim Width / 2 = Centerline
8" wide rims / 2 = 4" Centerline |
Measuring Maximum Backspacing
Measuring Bolt Circles
Adapters
Adapters move the rim further out. They let
you bolt on rims with too much backspacing. If you decide you want to bolt on a pair of
Corvette ZR1 rims (17x9.5", 50mm Offset) you would first need to calculate the
backspacing.
9.5"
/ 2 + 50mm / 25.4 Offset + 0.25" Lip = 6.97" Backspacing
Rim Backspacing - Max Backspacing = Adapter Thickness
6.97" - 5" = 1.97" Front Adapter Necessary
6.97" - 5.85" = 1.12" Rear Adapter Necessary
Ideally, you would want some clearance on the inside of the rim to compensate for suspension movement, etc. In this case, we recommend 2" adapters for the front and rear. You can run the 2" adapters in the rear, even though you only need an extra 1.12" backspacing. This will move the wheel further out in the wheelwell, matching the front, and the wider track will help cornering as well. The only time to not match the front adapters is when you have wider wheels in the back (17x11 ZR1's for example). In that case, the wheel will fit in the wheelwell if the 1.25" adapter is used, but will protrude past the fender lip if you have a wider than necessary adapter.
For all fourth-gen rims - 2" adapters front and rear should be used on a third-gen. Some folks prefer having a thinner adapter in the rear. This will fit fine, but the rim will be inside a bit compared to the front. The same thickness on the front and rear gives a more balanced look than using thinner adapters in the rear (with the same size rims f&r) For C5 and 17x11 ZR1 rims, please do the math!
Using a 4th Gen Rear
If you've changed your third-gen rear to a 4th gen rear, you do not need adapters. The 4th
gen rear is approximately 2" wider per side. This is the same as using a set of 2"
bolt on adapters
Adapter Design
You have two choices when the rims need to be moved out - slip on spacers or bolt on
adapters.
Slip-on Spacers
These are the discs that slide over your studs. For small thicknesses (1/4" or less)
they are fine. For greater thicknesses, the wheel studs are seriously weakened. The reason
is that the studs have a greater bending moment since the lugnuts are further away. Under
braking or acceleration, the studs would be stressed more, and might break.
Bolt-on Adapters
Billet adapters bolt onto the car just as a wheel would. The adapters have their own studs
that the rim bolts onto. This design is just as strong as without adapters, since the stud
forces haven't changed. The adapters are made from a billet cylinder of 6061 T6 Aluminum.
The billet is machined to fit over the hub, with stud holes drilled to fit. Studs are
pressed through the adapter to which the rims are bolted onto. The adapter is then slipped
over the car's studs and bolted on. The rims finally bolt on as usual.
There are two ways of bolting the adapters to your hub. One uses a lugnut with a long shank and washers. The clearance needed for the holes ends up as a slight bit of slop when they are bolted on. This isn't usually noticeable when driving. The other method is to use acorned lugnuts to bolt on the adapters, just like for the rims. The lugnuts center the adapter when they are tightened. This is a significantly more precise way to bolt on the adapters, and is how we make them.
Various Rim Dimensions
| Rim Name | Size | Offset | Backspacing | Suggested Thickness (3rd Gen) |
| Corvette 84-87 | 16x9.5 | 38mm | 6.6" | 2" |
| Corvette 88-96 | 17x9.5 | 56mm | 7.3" | 2.25" |
| Corvette GS ZR1 style | 17x9.5 | 50mm | 7" | 2" |
| Corvette ZR1 style (Low Offset) | 17x9.5 | 38mm | 6.7" | 2" |
| Corvette ZR1 style (Low Offset) | 17x11 | 36.5mm | 7.397" | 1.25" Rear |
| Corvette ZR1 style (High Offset) | 17x9.5 | 56mm | 7.4" | 2.25" |
| Corvette ZR1 style (High Offset) | 17x11 | 50mm | 7.93" | 2" Rear |
| C5 Corvette 97-2000 | 17x8.5 front | 56mm | 6.8" | 2" |
| C5 Corvette 97-2000 | 18x9.5 rear | 63mm | 7.6" | 2" |
| C5 Corvette Z06 | 17x9.5 front | 54mm | 7.2" | 2.25" |
| C5 Corvette Z06 | 18x10.5 rear | 58mm | 7.9" | 2" Rear |
| C6 Corvette | 18x8.5 front (new 88967389, old GM 9594351) | 56-58mm depending on where you see it | 6.53" | 2" Front & Rear |
| C6 Corvette | 19x10 rear (new 88967390, old GM 9594353) | 79mm | 8.11" | 2.25" Rear |
| C6 Corvette Z06 | 18x10 front | |||
| C6 Corvette | 19x12 rear | |||
| Camaro 82-92 | 16x8 front | 0mm | 4.35" | |
| Camaro 89-92 | 16x8 rear | 16mm | 5" | |
| Camaro F1 ZR1-style | 17x9 | 50mm | 6.8" | 2" |
| Camaro 93-97 | 16x8 | 55mm | 6.5" | 2" |
| ROH ZS | 17x9.5 | 5 mm | 5.472" | |
| ROH ZS | 17x8.5 | -7 mm | 4.5" |
Disclaimer - These dimensions have been gotten from many sources, and are not verified. Use at your own risk. If you see an incorrect number, please let us know. The suggested thickness may not match based on offset numbers. They are based on experience fitting those specific wheels to third-gen f-bodies, and reflect feedback from customers.