Thanks Russ! Thats odd that you had some rub with 31 x 10.5's on stock rims. My 1st Monty (the blue 89 LS) was bought with stock aluminum LS rims and 31 x 10.5's installed with no rubbing at all.

The reason I asked specifically about the backspacing (and might as well the offset too) on 15x8's that I was thinking about going with something different that stock Mitsu rims. 15x7's are too hard too find, and since I'll be using 31x10.5's again, 15x8 seemed perfect.

So on those 15x8's , I'm speculating on the allowable range of backspacing (3.25 to 4 or maybe even 4.25"?) and the range on the offset (per wheel faq, -6mm, but is 20 to -20mm OK?)

I really like the ATX (American Racing) Chamber series. i think there was a board member way back who used them, but not sure how well they worked in the long run. I seem to remember finding his post about them, I asked how well they worked and dont remember seeing a reply. An expensive premise to "try" for sure.

Soft 8's are OK, but I'm looking for something else I suppose.

Jim