Hmm, the rears fit much better than expected, the fronts not so much.
It looks like I had the wrong info on size/offset for the C6 Z06 front wheel. Now searching, I still cannot find a consistent answer of what stock actually is.
Reproductions vary over the place in offset availability, and that's all I'm finding for answers.
If you pull one of those front wheels off in the near future, can you do a backspace measurement for me? (lay a straight edge across the rear lip of the wheel, and measure down to the hub surface).
I was under the impression they were 18x9.5" -50mm offset, which would put them at 7.22" backspace (or 3.28" out, from hub to outer lip edge). If this is what they were, then they would fit fine and not stick out like that.
Now searching more, I'm seeing either 18x9.5" -40mm (6.82" backspace - 3.68" out), or 18x10"-40mm (7.07" backspace - 3.93" out) as being OE.
I guess I did warn you they would stick out of the fenders some, shame on me for being wrong on which end of the car it would happen.
