Can anyone tell me what the minimum amount of backspacing I need on a 17 X 8.5 wheel? My car is a 1994 Z28.

 

A 6" backspace on an 8.5" wheel would put the outside edge of the wheel/tire close to the outside edge of the fender in the front. It would be moved out approx. 1.20" further than the stock 16x8 wheel sits. In the back, the 6" BS would still be under the fender.

Just as a point of reference, the outer edge of wheel/tire in the front would sit just about where this 17x9.5 TT II sits, and in the back, it would be about 0.7" deeper in the wheel well than the 17x11 TT II on the black T/A:

http://www.kellydrown.com/showcase/120-2036_crw_std.jpg

 

Could I run a wheel with 5.5 in backspacing?

 

In the back, it would look just like my 17x11 wheel/tire combo, as far as how close it is to being out from under the fender. While a wheel/tire combo that is almost 12.5" wide looks "OK" sticking out that far, a wheel/tire combo that is 3.5" narrower is going to look like the car is running on outriggers, IMHO. You have to decide if you like that look.

http://cjcfo.fbody.com/members/injun...C/RrView01.jpg

In the front, the wheel/tire will stick out about 1" more than the 17x9.5" wheel tire combo on the front in this picture.... its gonna be outside the fender.

http://cjcfo.fbody.com/members/injun...C/Rr34Dr02.jpg