GTS Wheel Dimensions

Does anybody have (or can you direct me) the dimensions of rear wheel for the GTS? SCCA spec line says I can run BBS or CCW, but it does not provide back-spacing and/or offset. I am going to thumb my nose at the SCCA establishment and run Forgestars (for half the price) but I need to tell them what I need. Currently, I have 17X10's with a +23mm offset. They are perfect in the front with 275/40/17 Continentals. In the rear, they look like space-saver spares. I want to run the 18x11's in the back.

As always, thanks in advance!

Most of us run CCW 18" wheels. SCCA would be 18x11 rear and 18x10 fronts. NASA and others will let you run 3 piece 18x12.

I suspect the CCWs are expensive but 100% reliable and very good support / quality.

I doubt SCCA tech would ever know the difference, but would possibly measure width. Will be hard to get offset right w/o copying a set.

Are you running 17" front and 18" rears?? That would be a strange set up. The main advantage of 18" wheels is the availabilty of slicks which are no longer made in 17". We had best luck with Hoosiers, bad perfromance with Avons and never tried Michelins... but they are by far the fastest on 997 Porsche Cup.

cheers.
KB

Sorry, I got so "wordy" I realize I failed to make my question clear. What I need is the offset and/or back-spacing for the 18X11 wheels.

I have 17X10's with 275/40's all around now. The fronts fit fine. The offset is perfect as the wheel/tire fills the wheel arch opening nicely. However; in the rear, the same tire/wheel is consumed by the wheel well opening. The tire is easily 1.5" inset, and it looks like the combo is way too small for the car. It looks ridiculous. So since I currently only have one set of wheels for the car, I figured I'd get two sets of wheels for the rear. 17X10's in the front, and 18X11's for the back. I was just wondering if anybody knew the offset of the 18x11's.

Every C5 Corvette ever made left the factory with 17" front wheels and 18" rears.