1970 dart max wheel size

[Jakeandruby]

I have a 1970 dart and I’m getting an A body 8 3/4. My question is I want a 15x8 and I think I found one that will work and just want to check. It’s a 15x8 with 4 1/2 backspace. Stock everything. I also want to know about tire sizes. 255, 265, 275? I just want to make sure before buying.

 

[72bluNblu]

Small bolt pattern axles or large?

With the springs in the stock location 255 is the widest you can go. Some cars more like 245, it depends on the body tolerances on your car.

 

[Jakeandruby]

Small bolt pattern axles or large?

With the springs in the stock location 255 is the widest you can go. Some cars more like 245, it depends on the body tolerances on your car.

they are large bolt pattern

 

[72bluNblu]

Well, if my ‘71 Dart is any indication then a 15x8 with 4.5” of backspace paired with an A-body 8 3/4 with BBP axles won’t be enough backspace to max out your tire size.

On my car the wheel mounting surface to the stock spring location is 6”, but it’s only 5” to to the quarter. To center the rim, which you’ll have to do if you want to max out the tire size, you’ll need a 1/2” of offset (13mm, since offset is always measured in mm). So your 15x8’s would need a +13 offset, or a 5” backspace.

But you should definitely measure your car before you start spending money. Some have less room than others, and some are even different from one side to the other.

 

[toolmanmike]

15x7 with a 4.25 backspace and 255r60-15 is all I could fit on mine without trimming. You need to do some careful measuring before you pull the trigger on anything.

 

[72bluNblu]

15x7 with a 4.25 backspace and 255r60-15 is all I could fit on mine without trimming. You need to do some careful measuring before you pull the trigger on anything.

You've still got the SBP axles on yours though right?

 

[Syleng1]

This has come up about 50 times please use the “SEARCH” feature.

 

[toolmanmike]

You've still got the SBP axles on yours though right?

Yes. How much and what difference do the big bolt axles make?

 

[doug 371]

Yes. How much and what difference do the big bolt axles make?

The distance from the bearing to the flange is greater on big brake axles...think it's about 3/8" per side...

 

[toolmanmike]

So a little more backspace for the same wheel width. My 7's and 255's are very close to the fender lip on the drivers side and probably only 1/2" clearance on the spring side. Now, 255's on 7" wheels do have a bit of sidewall bulge. May be a narrower tire would give a little more clearance. Let's put it this way, I don't have any need to try a 8" wide just to say I can. I wouldn't want to trim or roll the lip to make it happen.

 

[JoeDragster]

At some point cost vs need vs reality.

measure twice and cut once is the old saying.

 

[Mtrhead]

Trimmed my lips of quarters and was able to install a centerline 8.5 width with a 265/60/15...deep offset...prolly 5"

 

[toolmanmike]

Trimmed my lips of quarters and was able to install a centerline 8.5 width with a 265/60/15...deep offset...prolly 5"

Looks like you have a Duster/Demon. Those wheel houses are different than Darts.

 

[72bluNblu]

Yes. How much and what difference do the big bolt axles make?

The distance from the bearing to the flange is greater on big brake axles...think it's about 3/8" per side...

5/16” is the number, that’s the change in the flange stand off going SBP to BBP. So, add a 1/4” to 1/2” to the backspace. The offset to center the wheels with the BBP axles is about +13, the factory 15x7’s with a 4.25” backspace are +6.

So a little more backspace for the same wheel width. My 7's and 255's are very close to the fender lip on the drivers side and probably only 1/2" clearance on the spring side. Now, 255's on 7" wheels do have a bit of sidewall bulge. May be a narrower tire would give a little more clearance. Let's put it this way, I don't have any need to try a 8" wide just to say I can. I wouldn't want to trim or roll the lip to make it happen.

Yup, that’s a good point. 255/60/15’s are measured on a 7.5” rim, so putting them on a 7” will squeeze them a little and putting them on an 8” might stretch them a little compared to the published specs. It’s a small difference either way, but 255’s are a tight fit.

For the BBP axles you’d want a 15x7” with at least 4.5” backspace.

Looks like you have a Duster/Demon. Those wheel houses are different than Darts.

Yes they are!!! By about a full 1”.

275’s will fit a Duster/Demon/Dart Sport with no cutting at all with the right backspace. Can’t do that with a Dart unless you install a 1/2” offset on the springs.

 

[Mtrhead]

70 dart swinger

 

[DartGTDan]

I borrowed these wheels & tires from Ken (aka FABO member 72Dart6pack) to see if/how they fit my Dart GT. My car has the factory installed 8 3/4" small bolt pattern rear-end, stock spring location, but does have (courtesy of the previous owner) Mancini 2800lb SS springs.

According to Ken, these 15" X 7" wheels are from Wheel Vintiques, & according to Wheel Vintiques' website the wheels have 4 1/4" back spacing. The (13 year old) tires are 235-70R15.

I am able to fit all my fingers between the sidewall of the tire and the quarter panel.

This last pic shows the 15" X 7" (P235-70R15) on the driver side and the 14" X 5 1/2" (P215-75R14) on the passenger side.