275/60/15 woes

xguard said
I've read you can fit 275/60/15s on a 72 Demon if you nail the back spacing. Looks like I missed it. 15x8s with 4.5 back space. That seemed to be the magic formula. But my car is small bolt pattern with the standard 10 inch drums. Maybe that's the difference. Thoughts? Options? Really limited on wheel options for small bolt pattern. (Btw the back of the car is sitting a little higher because of the weight distribution on Jack stands.) Will probably throw some 255s on the old wheels until I can upgrade to big bolt pattern.

View attachment 1715596987

View attachment 1715596988

View attachment 1715596995

The 15x8" with 4.5" of backspace is generally the "magic formula" for a Duster/Demon that has an A-body 8 3/4 that's been converted to BBP axles. With the stock SBP axles 275/60/15's need more like 4.25" backspace. But with the body tolerances on these cars it's always a good idea to measure your own car from the wheel mounting surface back to the springs and out to the quarter lip. It's not unusual to have an axle offset slightly to one side or the other, or the body tolerances to be more than a 1/4" different from one car to the next or even from one side to the other.

Looks to me like a thin spacer will fix the issue, your car is high enough in the back that the quarter clearance shouldn't be a big issue. If you can get to 3/8" or so clearance on the springs you should be ok. Always better to have a little too much backspace than not enough, a 1/4" spacer is no big deal at all as long as you have enough threads on the wheel studs and it's a lot easier to install a spacer than move the quarter lip.

TF360 said
4 1/4 backspace with 255's - Don't go bigger unless you want to problems

TF360 said
Sireland, I cant believe how much space you have on the outside- You don't get that on a 74 Duster

There are literally DOZENS of Dusters/Demons/Dart Sports running 275/60/15's on 15x8's on this board without issue. As I already mentioned the body tolerances on these cars were not super accurate, so it may be that your car can't run tires that size without modifications. But based on my own '74 Duster and many I've seen on this board it's much more likely that 275's will fit without "problems" if the backspacing is done correctly.

I had 275/40/17's on my '74 Duster with decent clearance for the street, and I'm currently running 295/35/18's with a 1/2" spring offset and some quarter lip trimming. 275's are tight, but they will fit most Dusters/Demons/Dart Sports as long as you account for the differences in width of the different axles and bolt patterns available for those cars.