I am widening some 18x8.5 (38mm offset and 6 3/4 BS) adr sterlings to either 10" or 10.5".

If I widen to 10" I have a 58mm offset and a 7 1/4 BS.

If I widen to 10.5" I will have a 64mm offset and a 7 3/4 BS

What is the max. backspacing you can run? I don't care about offset I wanna know BS.

I hear guys running 15x10's with 7 1/2 BS. how well does that fit?

Should I just stay safe and go with the 10's or go 10.5" and possibly have to run a spacer?

 

7.93" is the max BS, based upon a 17" x 11" 50 mm offset ZR-1 replica.

 

Nope, those wheels have 7.50" backspacing

 

With 18's, you can run a 8" backspace with a little BFH work.