Ideal backspacing for rear wheels

Hey guys:

I'm going to be upgrading wheels on my '77 Caprice coupe from an ancient set of Vectors to 8" Ralleys. I already have a nearly new pair of 255/60/15's I plan to use for the rear, so what amount of backspacing will get things out to near the fender lip without rubbing? Thanks.

Welcome to the forum!

Using an 8" wide wheel, 3" backspacing will put them pretty close to the wheel lip without rubbing.  Using 255's, 2" might even work better.  

Here's a pic of 15x10 Rally wheels with 5" backspacing (295/50 tires).  When using an 8" wide wheel, 3" backspacing will put it in a similar position.

Here  is the same tire\wheels with a 1" spacer behind the wheels .



Although it is a different Rear end anyone know the width difference between a 7.5 79' rear and 95-96 Posi 8.5?

Myloth wrote:<snip> Although it is a different Rear end anyone know the width difference between a 7.5 79' rear and 95-96 Posi 8.5?

IIRC, one inch wider. (1/2 inch on each side)

I thought the tires stuck out a tad more so that's actually 1.5" out from the stock rear in the first pic .