What gets me, however, is the differences between the actual wheels or wheel manufacturers themselves.
If you look at the blue Shell Valley car below (courtesy of Luc and Club Cobra gallery), this car uses 15x10 Team III's with a 4.5" backspacing. Note how shallow the rear wheel looks. It doesn't look deep at all.
Now if you look at the picture below that (courtesy of
www.ffcobra.com wheel gallery), this FFR uses a PS Engineering 15x9.5 with a 4.25" backspacing.
If you glance back up at my wheel comparison drawing, you'll see that there really isn't that much difference between the two. The 9.5" wheel is of course smaller, but if anything the "dish" in the wheel should be more shallow.....but if you look at the FFR, the wheel looks twice as deep as the Shell Valley car.
This leads me to believe there are differences in wheel manufacturers and how thick their mounting flanges (or wheel centers) are......I guess if you have a thinner flange, it would leave more room for a deeper dish.
If anyone else has any insight, I'd love to hear it.