rear tires not centered in body

[Steven190]

I have a 8.75" rear end out of a A body in a 69 Dart. trying to use 15 X 8 with 4.75" back spacing.
Tires are 255/60-15"
My problem is the left side fits, but tight, the right side is 5/8" out. It is 5/8" towards to fender, into the lip. The rear axle is centered in the body, the disc brake kit fits the housing and rotors, the axles have the green bearings, so they are the correct length.
There is 3/4" between the tire and the leaf springs on both sides. I have double checked the measurements of the body and they are the same side to side and the rear quarters look very straight and the trunk and doors have the correct gaps.

This is driving me nuts, was wondering if there are any ideas? I thought about getting a 5" backspace just for the right side, but nut sure if it would look good or even help.

Any suggestion are welcome.

 

[jdsduster]

I have a 8.75" rear end out of a A body in a 69 Dart. trying to use 15 X 8 with 4.75" back spacing.
Tires are 255/60-15"
My problem is the left side fits, but tight, the right side is 5/8" out. It is 5/8" towards to fender, into the lip. The rear axle is centered in the body, the disc brake kit fits the housing and rotors, the axles have the green bearings, so they are the correct length.
There is 3/4" between the tire and the leaf springs on both sides. I have double checked the measurements of the body and they are the same side to side and the rear quarters look very straight and the trunk and doors have the correct gaps.

This is driving me nuts, was wondering if there are any ideas? I thought about getting a 5" backspace just for the right side, but nut sure if it would look good or even help.

Any suggestion are welcome.

maybe a quarter panel was replaced,and wasnt just right

 

[supertruck]

First thing I would check is if the spring perches have been moved. While I'm not sure about your particular rear end, it's not uncommon for the pinion to be slightly off center by design once it's in place. I've found that on quite a few Ford 9 inchers. Someone may have moved the perches in an attempt to center the pinion in the frame before you got it. Are you sure that the wheels are not too wide even if you get everything else lined up?

 

[Steven190]

Sorry, when I said the rear end was centered, I mean that the center of the housing is centered not the pinion. Which is a little offset. The spring perches are 44" apart and the same length, there is just enough room for the U bolts to fit in between the pad and the weld on the flange straight up and down. The axle looked to be stock, with no re-welding or grinding marks, but it maybe.

Were the tolerance is on the flat side on the fender, the very top of the arch.
This is the combo that, most here, are running with a 4.5" backspace, I measured the backspace and came up with 4.75" with the 255's

 

[toolmanmike]

Dang, tonight I tried some 15x7 (4.25 backspace) Rallys with 255-60/15's. The right side had plenty of clearance inside and out but the drivers side was quite tight. (barely a finger width on the inside and outside.) I hope I don't ruin a tire but it could happen. I imagine the quarter was fixed before paint and I would estimate the tub is a inch smaller on the drivers side.

 

[Dodge33]

Sorry, when I said the rear end was centered, I mean that the center of the housing is centered not the pinion. Which is a little offset. The spring perches are 44" apart and the same length, there is just enough room for the U bolts to fit in between the pad and the weld on the flange straight up and down. The axle looked to be stock, with no re-welding or grinding marks, but it maybe.

Were the tolerance is on the flat side on the fender, the very top of the arch.
This is the combo that, most here, are running with a 4.5" backspace, I measured the backspace and came up with 4.75" with the 255's

I believe the C to C on the factory spring perches on the A-body 8.75 to be 43 inches, and the factory B-body rears were 44 inches, center to center.

 

[pomonamissel]

when i built my 15 x 8's their had a 1/2'' inboard on eash side , tires were very tight on the stock located spring though . but leaving the springs and wheel opening lips alone . i got a 225/70-15 in/out with ease .

 

[72bluNblu]

I believe the C to C on the factory spring perches on the A-body 8.75 to be 43 inches, and the factory B-body rears were 44 inches, center to center.

Yup. If the perches are 44" apart center to center that's a B body rear end measurement. But if the 255's fit at all on 15x7's with 4.25" of backspace then it was shortened to A-body width, because that backspacing wouldn't work with those rims and tires with a B-body width rear axle.

If the tire and spring gap is the same though it probably isn't the perches being off center, it sounds more like the problem is the quarter/tub and not the axle not being centered to the frame. Body tolerances on these cars aren't great, the suspension points only had to be +/- a 1/4" from the factory. And if the quarter and wheel tub was replaced some point, anything is possible.

 

[famous bob]

Yup. If the perches are 44" apart center to center that's a B body rear end measurement. But if the 255's fit at all on 15x7's with 4.25" of backspace then it was shortened to A-body width, because that backspacing wouldn't work with those rims and tires with a B-body width rear axle.

If the tire and spring gap is the same though it probably isn't the perches being off center, it sounds more like the problem is the quarter/tub and not the axle not being centered to the frame. Body tolerances on these cars aren't great, the suspension points only had to be +/- a 1/4" from the factory. And if the quarter and wheel tub was replaced some point, anything is possible.

speaking of rear ends, does anybody know exactly what to measure off of, to check for rear end being squared up right? wonder if the trans crossmemeber would be good ?

 

[Steven190]

I used for side to side. Found the center of the axle. The rear side. the opposite of the pinion. I measured from the inside of the frame rails to the tape that has the mark for the center mark. For the rearward measurement I did the spring perch back to the axle. The axle was on the springs clamping bolt. There is not much room to move the axle.

I will have to re-measure the spring perches. I may have measures from outside to outside of the perch. As I said the axle was not modified when I got it. If it was it was an excellent job, just as it came from the factory.

I will post pictures later today of the axle and the tolerances of the fenders.

 

[RedFish]

Theoretically the b-body rear bolts into a-body without moving perches. leaf springs have enough free motion to flex outward 1/2 inch both sides, maintaining axle center to body.
So, theoretically, One or both springs might refuse to play fair and shift the rear left or right by X inches.
Regardless what is req'd to fix, problem is in the springs positioning.

 

[mguner]

If one side fits and the other doesn't then correcting the stress on the springs by moving the perches should make it tighter on both sides. This then requires trimming the inside of the lips which generally have about 3/4" to play with. Then there is also the possibility of rolling the lip with a bat or tool made for the process. Because one side is off just means that forcing the B body rear on the narrow spring mounting is pushing to the side with the most play or wear in the bushings. You could loosen the U bolts and see if you can center it a little better but I would remove the stress. If your wheels are 5 on 4" pattern this is not a B body rear axle though.

 

[Steven190]

It seems everyone is fixated on the B body 44" measurement, but like I said I re-measured it and it is 43". The axle measures 52.625" flange to flange.

Been thinking about getting a 5" backspace for the right side and rolling the lip of the fender.

 

[mguner]

Ok. We are good on A body rear. Is the measurement from the inner wheel wells the same to the tire? It looks to be as the seams on the trunk extension line up with the inner tread rib on both sides however the right bottom quarter is into the tire more than the left as your problem is described. What would be good to know is the measurement from the tire to the outside of the wheel lip on both sides. Looking down the side of the car does it look the same as far as body lines on both sides?

 

[mguner]

I still think you can loosen and straighten the u bolts and shift the axle a bit and then trim the inside lip with a whiz cutter and be ok.

 

[Steven190]

Ok. We are good on A body rear. Is the measurement from the inner wheel wells the same to the tire? It looks to be as the seams on the trunk extension line up with the inner tread rib on both sides however the right bottom quarter is into the tire more than the left as your problem is described. What would be good to know is the measurement from the tire to the outside of the wheel lip on both sides. Looking down the side of the car does it look the same as far as body lines on both sides?[/QUOTE


The left side measures 1 7/16" and the right side is 15/16"
I had the tape flat against the fender lip looking straight down at the tape.

So I am 1/2" off on one side. I have elongated the location hole on the pad and moved the axle to the left 1/4", but it made the U bolts and spring leafs canted.

The reason I put it on the forum is the feed back Maybe I am too anal about this but my feeling is it should be closer than it is. I am not adverse to rolling the lip.

just came from Amarillo, did the wind farms there. Love Abeulo's, too bad about the Mopar's at the Canyon

 

[2 Darts]

Is it possible the car was involved in an altercation that left the unibody structure out of alignment?

 

[replicaracer43]

I still think you can loosen and straighten the u bolts and shift the axle a bit and then trim the inside lip with a whiz cutter and be ok.

Absolutely, you can even slot the hole in the perch, and u bolt bracket and shift the rear slightly. Its just "tolorence stackup" its very very common.

 

[Dave1967]

IMO. Your quarters are hung a little off. Your spring perch is correct. Your reveal to tire to spring is the same on both sides. Frame rails are straight to each other. Front spring anchors could be off or quarters are off. Do you really think at the factory in the 60's much was given to detail. All these cars came with small tires so who cared about a 1/2" on reveal that was huge with factory tires. On my 67 fb fish the quarters are off by a 1/2" and the front spring plate is off a 1/4". This would never have been picked up till i put 15 x 8 rims and 275/60/15 MT cheater slicks.

 

[replicaracer43]

Its a lot simpler to slot a hole and center a rear axle than it is to rehang a quarter panel.

 

[RustyRatRod]

This is a VERY common problem on these cars. I don't think any of them were perfect. It's probably never been involved in an accident. I have never seen one to date where the wheel houses had the same measurement. As long as it was close, the car got put together. Period.