65 barracuda need help with rim backspacing

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zoltan c

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Abbotsford, BC. Canada
OK, so I have an E-body housing for my 65 barracuda and I want to narrow it to the stock A-body length so I can buy stock A-body axles instead of getting custom axles at a greater cost. I took some measurement of the rear tubs and the axle to see what kind of backspacing I would have to get on the rims and how much rubber I can stick under the car. The rear spring are getting moved in to the frame rail and I have a set of SS springs.

The stock 8 3/4 drum to drum measurement is: 57 1/8"
The 7 1/4 drum to drum measurement is the same at 57 1/8", so I took the measurements with the 7 1/4 in the car.
The tubs are 12" wide, from the axle flange to the outer fender is 5 1/4" and to the inside wheel tub it is 6 3/4.

I think that the maximum tire sectional width should be about 10.5" which means that I would be able to use either an 8" or 9" rim. As for the backspacing it would have to be 4" plus 3/4" (on an 8" rim) because the axle flange is that much closer to the outer fender. And it should be 4.5" plus 3/4" on a 9" rim.
I also want to run the tallest tire I can because I have 4.30 gears in the pumpkin that is going into the 8 3/4.
If this makes any sense whatsoever to you guys can you let me know if my calculations are correct and what kind of backspacing do some of you run on your 64-66 barracudas. Thanks, sorry for the long explanation.
 
keep in mind - rim measurements are from bead to bead... NOT the lip of the rim... if you get a 10" rim it's 11" wide due to the lip that protrudes out where the balancing weights would go.

I run a 17x7 w/ 4.25" backspacing and have room outside, ( about 3/4 " and 1/4" inside with a 255/45/17 tire
 
I run a 4 and 7/8" back space on 15X7" centerlines very close to leaf springs with tire and about an 1.25 to outer fender.

15"X 8" would be perfect with my backspacing but next wider centerline is 15"X8.5" I don't think that would fit my stock 66 car.
 
Are you moving your springs in to the frame rail or just using the offset hangers? I don't think there's an advantage to moving them in to the frame rails unless you plan to enlarge the wheel tubs, which will require alterations to the area under the rear window in an early Barracuda.

I'm kinda' in the same situation as you are. I have a set of 15 x 8.5" wheels with 5" backspacing (6mm positive offset). If I use these wheels with a stock A body 8 3/4" rear & offset spring hangers, I think the wheel will be nearly centered in the wheel tub. I think I might need to narrow my rear slightly (maybe an inch or less, I haven't made my final measurements). I'm hoping I can do this & still use the stock axles by switching to "green" style bearings & removing the thrust block to let the splines go a bit farther into the diff. I'd really like to fit a 275 tire in back, but haven't decided for sure yet.

I think a tire 28" tall will fit but I might need to move the rear axle back a bit to center the tire front to back in the wheelwell. This should be simple when using the Mopar spring perches since they have an extra set of holes in them. I'll need a longer driveshaft but I need to have a new one made anyway.
 
I already bought the spring relocating kit so I will use them, but also it will let me move the axle back slightly to better center the wheel front to back. I didn't know that you could also accomplish this with the offset hangers. I thought about using spring sliders on the rear as well.
 
I checked the link you posted and I can't believe how reasonable the prices are! Unfortunately here in Canada they want to charge me $250 plus tax (12%) just to narrow the rear. That's without new housing ends. I don't know how much to re-spline axles but I'm sure it won't be $100. LoL! Plus I only have the E-body axles which taper down and can't be re-splined which means I would have to buy some A, B-body axles. So, it may be cheaper for me to just find some wheels that will fit instead of beating my head against the wall.
 
What do you guys think of the Salt Flat Specials from American Racing? They are a two piece wheel and can be ordered with a custom off-set.
I did a little more research on what will fit and I figure that you need a 12mm off-set on the rear wheel on a 64-66 cuda with a standard width A-body axle.
15X8
5.0 backspace (5.25, 5.5 will also work)
12mm off-set

This chart shows what backspace you get with what off-set.
 
I really like the Salt Flats Specials. I thought about them for my car, but didn't think they were available in the 4" bolt pattern (You mentioned you wanted to use stock A Body axles). I think they would look good on your car.
 
I have switched the front over to 5 on 4 1/2 bolt pattern and plan on getting axles with the same big bolt pattern. The wheels are available for 5X4.5" I like the wheels, but they are a little expensive.
 
zoltan c said:
I already bought the spring relocating kit so I will use them, but also it will let me move the axle back slightly to better center the wheel front to back. I didn't know that you could also accomplish this with the offset hangers. I thought about using spring sliders on the rear as well.
Click to expand...

the slider are pretty trick. i have mine just tack welded in case i have to add spacers to raise the rear of the car once i get all the weight on the rear.

cuda rr slider.JPG
 
Sweatybetty, I was going to ask you for a pic of your lear spring set-up! Thanks. Any pics of you mini tubs? I think I may eventually tub mine as well. And I'll check that site about the leaf spring info. Thanks again.
 
I am working on the same thing. I made up a spacer for the front hanger to move the hanger back 3/4". offset hangers, I believe I will narrow 1"side from the perch to yhe end with e body back plates and axless. They stick out further than A body for the wider brakes. If you are going to narrow I would change over to the b,e,c axles for A body length. so you can get drums and brakes cheaper and easier.
 
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