I just noticed that they sell a Z06 wheel in a 8.5" width. If I chose to run that wheel up front compared to the 9.5" wheel then does that mean I would now need a 1" spacer instead of a 2" spacer? the 8.5" wheel has a 58mm offset. Id really like to cut down on the thickness of my 2" spacer I have now AND I will be adding Z06 brakes which willpush the wheel out a little bit as well.

 

I don't know all the metric offsets, but I would bet that the 1" width was taken off the back space, thus would require the same spacers.

 

It depends on the BS of the 8.5s Could be more, could be less, could be the same.

 

I'd assume they are a 56mm offset ('97-'00 C5's had 17x8.5 fronts with 56mm). If that's the same as the wheel you've got, then you take half the difference on the inside, and the other half on the outside. Find out the offset or backspacing, and know for sure.