Widest wheel and tire combo on 15x8 Ralley

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canucksdude

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Hey folks, if I was to buy some 15x8 ralleys from Summit/Jegs what is the backspacing I would need to fit the widest possible tire? It’s an 8.25 stock length rear end and never tubbed. It’s on a 72 demon. Could it fit a 275/60/15? Thanks folks been meaning to ask this for a few weeks! I know the boards will know.
 
It's been a while since I had a Duster but assuming your specs are "normal" whatever that is, about 4.25-4.50 for backspace. You should be able to fit a 275x60-15.

If someone jumps in that knows more than me - which is pretty much everybody - follow their advice instead. I would recommend mocking up what you buy and measure your fit before mounting your tires. There is a fair bit of slop possible back there. If you mount the tires the rims are not returnable.
 
275/60/15 will fit with the stock spring locations on a Demon as long as the backspace is correct.

A-body 8.25’s are narrower than A-body 8 3/4’s. With an 8.25” a 15x8 would probably need 4.25” or even 4” of backspace. Your best bet is to measure your car, you want to measure from the wheel mounting surface (drum face) back to the springs. A carpenters square works well for that purpose to keep all the measurements straight.
 
Hey folks, if I was to buy some 15x8 ralleys from Summit/Jegs what is the backspacing I would need to fit the widest possible tire? It’s an 8.25 stock length rear end and never tubbed. It’s on a 72 demon. Could it fit a 275/60/15? Thanks folks been meaning to ask this for a few weeks! I know the boards will know.

Yes it can. Its what I have on my 73 Duster
 
275/60/15 will fit with the stock spring locations on a Demon as long as the backspace is correct.

A-body 8.25’s are narrower than A-body 8 3/4’s. With an 8.25” a 15x8 would probably need 4.25” or even 4” of backspace. Your best bet is to measure your car, you want to measure from the wheel mounting surface (drum face) back to the springs. A carpenters square works well for that purpose to keep all the measurements straight.

thanks! But I am curious, where does a guy find ralleys with that backspacing. All the obvious places like jegs , year one, wheel vintiques, and cocker tire only have 15x8s with the 4.5 inch backspacing. Anybody know??
 
thanks! But I am curious, where does a guy find ralleys with that backspacing. All the obvious places like jegs , year one, wheel vintiques, and cocker tire only have 15x8s with the 4.5 inch backspacing. Anybody know??

They may need to be custom ordered. You may be able to use spacers to get to where you need to be, but you should measure first to make sure. I try to keep my plain wheel spacers at a 1/4" or less thick.

Just because a wheel is offered in a particular off the shelf backspacing doesn't mean that's what your car needs. Most of the other Mopar body styles can use a 0 offset wheel like that (15x8 with a 4.5" backspace is 0 offset). But an A-body 8.25" is narrower than an A-body 8 3/4, so with an 8.25" you need less backspace than what will work for most other Mopars, even other A-bodies with 8 3/4 rear ends.
 
They may need to be custom ordered. You may be able to use spacers to get to where you need to be, but you should measure first to make sure. I try to keep my plain wheel spacers at a 1/4" or less thick.

Just because a wheel is offered in a particular off the shelf backspacing doesn't mean that's what your car needs. Most of the other Mopar body styles can use a 0 offset wheel like that (15x8 with a 4.5" backspace is 0 offset). But an A-body 8.25" is narrower than an A-body 8 3/4, so with an 8.25" you need less backspace than what will work for most other Mopars, even other A-bodies with 8 3/4 rear ends.
 
So in the absence of getting custom backspacing, it would be a fairly safe bet a 255/60/15 on the 15x8 with 4.5 backspacing would fit just fine hey (on paper anyway)?
 
So in the absence of getting custom backspacing, it would be a fairly safe bet a 255/60/15 on the 15x8 with 4.5 backspacing would fit just fine hey (on paper anyway)?

“On paper” that combination will fit, but it may still be tight. Clearance to the springs would be about 3/8” by the math using my Duster when it had a 7.25” and I test fit a set of 275/40/17’s as the comparison.

As always, I’d say measure your car. The 255’s should work, but you don’t have much leeway to work with if the tolerances on your car don’t match mine. And with the larger sidewalls it’s possible you might still get some rubbing under certain conditions if you cut it too close.
 
15x8 and 4.5 backspace is too close to springs. 4.25 is minimum 4 " backspace is more ideal. Stockton wheel can custom make a set.
 
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