A Body wheels on a B body rear axle assembly

[Mr Wrinkles]

I have a 68 B Body 8 3/4 axle under a 73 A Body. Is anyone else running a combination like this? If so what would be the appropriate wheel offset & back spacing? Interested in running 15 versus 14 inch wheels. Thank you for any insight you may offer.

 

[72bluNblu]

What ‘73 A-body? Makes a BIG difference.

I have a ‘68-70 B-body 8 3/4 in my ‘74 Duster. I was able to run factory cop wheels, 15x7 with a 4.25” backspace with 225/60/15’s. That’s the widest that would fit, more backspace would be needed for wider tires. A Duster will fit a 275/60/15 with the right backspace, so 225 is a pretty significant reduction.

But on a Dart/Scamp you’d never even get a 225 to work on a factory wheel.

 

[Mr Wrinkles]

It's a 73 Dart Sport, so equivalent to your 74 Duster I would assume. So thinking your info would hold true.

 

[72bluNblu]

Yep, same wheel tubs and quarters.

So factory wheels should work for you if you stick with a 225/60/15 or smaller, 225's will be tight on the quarter lips. If you want to go with bigger tires, you'll need to add backspace. Your '68 B 8 3/4 is about 2.3" wider than an A-body 8 3/4 with BBP axles, so, you can add ~1.15" of backspace to whatever someone with an A-body 8 3/4 runs. For a 15x8 and a BBP A-body 8 3/4 you usually want ~4.5" of backspace, for example.

With your '68 B 8 3/4, for a 15x8 and say 275's you'd want ~5.65" of backspace as long as the springs are in the stock location (43" c-c on the perches). If you kept the B-body perches at 44" c-c, you won't be able to run that much backspace, or 275's.

 

[Mr Wrinkles]

The perches were moved to match the spacing of the original rear. So, room for the additional back spacing as described. I do appreciate the sharing of knowledge. This poor vehicle has never in its 41 years of my ownership had a set of four matching wheels. The time is approaching.

 

[duster2]

I have two 15 x 7 Magnum 500 wheels made for a B-body rear under an A -body , they have 5 1/8 backspace. They are for sale.

Frank
The Wheel Guy

 

[michiganpat]

Yep, same wheel tubs and quarters.

So factory wheels should work for you if you stick with a 225/60/15 or smaller, 225's will be tight on the quarter lips. If you want to go with bigger tires, you'll need to add backspace. Your '68 B 8 3/4 is about 2.3" wider than an A-body 8 3/4 with BBP axles, so, you can add ~1.15" of backspace to whatever someone with an A-body 8 3/4 runs. For a 15x8 and a BBP A-body 8 3/4 you usually want ~4.5" of backspace, for example.

With your '68 B 8 3/4, for a 15x8 and say 275's you'd want ~5.65" of backspace as long as the springs are in the stock location (43" c-c on the perches). If you kept the B-body perches at 44" c-c, you won't be able to run that much backspace, or 275's.

sounds perfect for a late 90's mustang wheel....the original 17x8 bullits are 5.72" backspace. a 255/50R17 is 27" tall....used to run those on my old M body with 3/4" thick bolt on spacers. wish I still had those wheels for my duster...