We're about to replace the stock wheels on my Dad's '02 SS with an aftermarket set, sized 17x9.5" all around.
I think the backspace we're after for this application is 7", but a search I performed showed only offset recommendations in millimeters.
Can someone please confirm that 7" is indeed the correct backspace for this application?

Thanks very much,
Rick

 

6.95 is the backspace recommended in the FAQ at the top of this page

I pulled this off the FAQ:
" As the wheel diameter increases, you can go to a larger backspace without hitting the steering knuckle. The knuckle slopes "back" from the spindle as you move upward on the knuckle. While a 17" wheel may be limited to a 7.45" backspace, you can use a slightly larger backspace on an 18" wheel"

 

The number quoted in millimeters is the "offset", not the backspace. You want an offset in the range of 45-56mm for a 9.5" wide wheel. The stock WS6/SS 17x9.0" 50mm offset wheels have a backspace of a shade under 7.0". A 9.5" wide wheel with a 56mm offset has about a 7.40" backspace.

The relationship of backspace to offset is affected by the size/shape of the lip that holds the tire bead on the rim. Offset is a precisely defined number. Backspace will vary slightly from manufacturer to manufaturer, or even among different wheel designs from the same manufacturer.