F-Body Europe

In order to determine the correct "offset" you need to be talking about a particular wheel width.

Offset is the distance the face of the mounting hub is displaced from the centerline of the wheel. Positive offset moves the inner edge of the wheel closer to the body, and reduces the amount the wheel/tire sticks out of the fender.

Backspace is the distance from the hub face to the extreme back outer edge of the rim and is equal to:

rim width/2 + offset + bead flange thickness.

The stock 16x8 wheels have a 55mm offset. That means that they have roughly a 6.65" backspace. If you take the "backspace" away from the total wheel width (nominal width + 2 flanges) you get "frontspace", or the amount the wheel sticks out from the face of the hub.

Stock: 16x8, 55mm offset, 6.62 backspace, 2.28 frontspace

WS6/SS: 17x9, 55mm offset, 7.12 backspace, 2.78 frontspace

I've run 9.5" wheels in the front, and the smallest offset I have run is 49mm. That made the backspace 7.14" and the frontspace 3.28". That put the outer edge of the wheel/tire just about where I wanted it. I believe the 17x9.5 Torque Thrust-II wheels for the F-Body have a 7.00" backspace and a 3.80 frontspace. To me, they are out a little toward the edge of the fender, but lets assume you could live with that.

In the rear, you can handle more "frontspace". My 17x11 50mm offset ZR1 replicas have a 7.93" backspace and a 4.00" frontspace. That is the max you can handle in the back.

Soooooooo....

For an 8" wide wheel - To keep a 3.80" frontspace, you need at least a 17mm offset. Any more than that, and you are outside the fenders.

For a 9" wide wheel - To keep a 3.80" frontspace, you need at least a 30mm offset.

For a 9.5" wide wheel - To keep a 3.80" frontspace, you need at least a 36mm offset.

All of this is APPROXIMATE, depending on the actual width of the flanges on the outer edge of the wheels that hold the tire beads on the rim.