Of running more backspacing on the rear wheels?

I know that andris’ site about wheel fitment/spacers says that you can’t run more then 5-3/4 or 7/8” backspacing in the rear without hitting, but I’m just not seeing what it would hit.

Just to make sure I took a set of 0 offset 15x8” rims (4.5” bs) and measured from the edge of the rim all the way around and the first thing that I see that gets in the way is the actual control arm, at 2-3/4” (making for 7-1/4” inches bs to hit it), and then the closest sheet metal appears to be at 3-1/2”…

Of course I know that you can’t go _that_ far in because the tires will hit the sheetmetal, but it looks like most of the offending sheet metal could be cut away/moved to fit something up to about 15x10 with 6.25-6-1/2” bs.

I’ve said it before that I suspect that the perfect wheel to get the biggest back drag tires (with some sheet metal massaging) would be a 10” width with 6 to 6.25” backspacing, but have never tried it because of the numbers listed on andris’ site…

What am I missing? The only other thing that seems to come close is the PB cable, but that looks like it would only be a problem if it’s flapping around and could be zip tied up and out of the way.

 

The control arm is A LONG WAY in from the first thing the tire will hit.

The FIRST thing is probably the bump stop. The next thing is the front of the inner fender well, at the front, at the very bottom; the portion that overlaps the front mount point for the LCA.

Stock 16x8 IROC wheels and tires only miss those 2 spots by about ˝". So whatever their BS is, add ˝", and that's just about it.

 

I never asked what will a _tire_ hit, but the WHEEL. Even with the thing jacked up pretty hard, the edge of the 15” rim is significantly below where the bump stop is, probably close to 2” or so, and it gets nowhere near the sheet metal that interferes with the tire.

Neither is at all a concern for me since, 1- they’re easy enough to move, 2- I know where the tire and tread sit with the size tire I want to run mounted on a 7” rim with the same offset, and it was a piece of cake to make room for them on my formula.

I’d rather mount the tire on a much more appropriately sized 10” (or possibly 9”) rim, but I want to tuck it in in the wheel well like I had the tire tucked in on the 7” rim, rather then the partially sticking out deal that most people settle for with 5.5” bs on a 10” rim (which does look kind of “tough” and old school, it’s just not what I want to do with the TA).

Offset wise, I’m looking to run something in between the stock 15” offset (1/2”) and the stock 16” offset (it’s supposed to be 16mm or 5/8”, but I’ve measured my formula rims to be right around 7/8”), which would work out to 6 to 6-3/8” BS on a 10” rim. If a 295/50/16 will fit on a stock rear 16” rim, so I know I can make room for something in the 275/60/15 range or slightly wider on the same offset. I’m just trying to figure out if the backspacing to get that same offset on a 10” rim will hit something, since that seems to be the implication of a lot of info out there but I can’t find anything that it would hit