Need some help controlling body roll

Suspension, Steering and Chassis

  1. Kipprc

    Kipprc Active Member

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    My 70 Duster has a lot of body roll. The tires rub the fender on turns. The tires are 255/60/15. The fronts are fine. It is just the rear tires. I know the shocks are worn and they will be replaced. The leaf springs look good, but who knows. I have never dealt with them before and I really am not sure if they are tired or were they selected by the previous owner for ride height. I thought about rolling the fenders, but the metal is too thick. I dont want to cut the fenders either. I just want to eliminate a lot of the body roll out the car. What would you suggest?
     
  2. Dana67Dart

    Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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    You could add a sway bar to the rear, but really the problem is too wide a tire, too low a ride height, wrong offset wheel.

    As you add weight (passengers) to the car it will only make the problem worse.
     
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    • 72bluNblu

      72bluNblu FABO Gold Member FABO Gold Member

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      A 255/60/15 should fit easily on a Duster if the backspace on the rim is correct. 275's should fit on most Duster's without rubbing when the proper backspace for the car is used.

      The springs may be sagging a little, but the spring rate isn't effected and the factory spring rates in the back weren't that far off compared to the front. If you like the current ride height of the car and don't want to replace the rear rims with ones that have the proper offset your next option would be sway bars. If you have stock torsion bars up front don't just add a rear bar, as the car will end up in oversteer. Add front and rear sway bars, which will help with the overall body roll. That's probably the easiest fix, if more is required you'll either need new rear rims or to start upgrading torsion bars and springs.
       
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      • Kipprc

        Kipprc Active Member

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        The car originally had the dog dish hubcaps with steel wheels. When they sent me a video of the car it had rally type wheels on it. The dealer had no idea of the history of the car so I am left to figure it out. I just want the cheapest option to fix it. I figure leaf springs will cost as much as rally wheels with the proper back spacing. The springs still may be bad. Somebody put black undercoating on without removing but the drivetain and the exhaust. I might as well try and get the proper wheels for the rear. I don't want to cut the metal. A sway bar may start off as the cheaper option, but could easily start costing more in the long run. Time for me to hunt for the proper size rally wheels and figure out what siz is on the car.
         
      • Kipprc

        Kipprc Active Member

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        OK so I measured it out and the backspace on the wheel is 4.5 inches. The wheel is a 15×8. I guess I would need another half inch of back space,, maybe a full inch.The leaf springs still look mighty tired to me, but they don't look bad. Might be a competition spring of some sort (4 leafs). They pretty much lay flat when on the ground. I need some advice on this as I am torn on what way to go. New set of springs vs. new rear wheels. I have added pictures for your inspection. Thanks in advance for any direction you can give me. Hopefully these photos aren't too large. If they are, I apologize.

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      • Oldmanmopar

        Oldmanmopar Going left turning right FABO Gold Member

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        One thing is the rims are wrong . the other is those long shackles with those old bushings. You probably have rear shift . Here are the proper 8 in wheels with 275 60's . No rub small bolt BS is 4 1/4 on primered Duster and gold Demon , Big Bolt back space is 4 1/2 orange Duster. Narrow the rear or buy the wheels that fit.

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        • Demonracer

          Demonracer 71 Demon 00 Ram 16 Chrysler 300S 05 Caravan FABO Gold Member

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          Get a good set of aftermarket leaf springs & do away with the extended rear shackles. Replace the shackles with OEM shackles, don't get the mind set for air shocks, they decrease the ride quality. You might also think about rolling the inner fender lip up so it gives you a bit more room. Just my .02.
           
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          • Kipprc

            Kipprc Active Member

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            Demonracer and Oldmanmopar, thank you. What would be the appropriate wheels for the car? As for the shackles/leaf spring debacle, I know nothing about them, but I am willing to learn. I will order a stock setup and do away with whatever is underneath the car. The rear end is a 8 3/4 the car started life witha 318 and whatever came with them back then. It now has a 340 (verified off of the block) Obviously one of the previous owners decided to change some things. They didn't leave a guide or receipts for what they changed out.
             
          • Demonracer

            Demonracer 71 Demon 00 Ram 16 Chrysler 300S 05 Caravan FABO Gold Member

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            OMM is correct about the wheels, you need to see who has what wheels for sale to fit as you want. By the looks of your springs, they are just about done, (i. e. flat). Get your tape measure & a flat bar to get measurements from the face of the brake drum to the inside of the inner fender to get your back spacing & look for wheels from there. If you are running the SBP, 5 lug on 4" bolt circle, you may have to go to after market wheels, if you are running BBP wheels, 5 lug on 4 1/2" circle, there are plenty of wheels out there & you can even go to 15" tires without a problem.
             
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            • Professor Fate

              Professor Fate Push the button, Max...

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              Okay, I'm going to muddy the waters a bit here, but try to follow my reasoning...
              If you truly do have 4.5" of backspacing on those 15x8s, those 255s should fit, no problem, PROVIDED YOU HAVE A STOCK WIDTH A BODY REAR END! From the look of your pictures, the amount of axle outboard of your springs makes it look to me like you've got a B or E body rear end in there. You need to break out the tape measure and figure out what you actually have- the spring perches were probably moved for installation in your Duster, but you need to verify the rest of the measurements. Use this thread: An accurate 8 3/4" rear axle width list
              Once you have confirmed what you have, then and only then will you be able to figure out what offset wheel you will need to center your tire in the wheel tub. Until you know what you have, anything else is pure speculation.
              As for your rear springs, they're toast. If you've got shackles that long on it and you're still having issues, they're done. Four leaf is a standard-duty spring, and they're 50 years old now. Lots of threads on this site about good vendors for replacement springs.
              But first, confirm what rear end you've got in there.
               
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              • 72bluNblu

                72bluNblu FABO Gold Member FABO Gold Member

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                Yup, I totally agree. If that was an A-body 8 3/4 with 15x8’s that have 4.5” of backspace then 255’s should fit just fine. That’s not an A-body 8 3/4. I would bet that’s a B body rear axle in there.

                That brings up another issue though. The rims may not have enough backspace for your rear axle, but they are the right rims for the car. And to get more backspace on a set of 15x8’s you will likely need custom backspace wheels.

                The shackles have to go, those extended shackles screw up the suspension geometry and don’t work all that well anyway. Fun fact about the leaf springs though, they were designed to be zero arch springs. So the fact that they’re almost flat at ride height means they’re not far from where they normally are anyway. Guys that run SS springs are used to seeing a heavy arch on the springs, but that’s not stock. The previous owners no doubt tried to raise the car to make up for the fact that the wheels stick out too far and hit the body. With the right wheels, you wouldn’t need to raise the car.
                 
                Last edited: Jun 10, 2020
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                • Kipprc

                  Kipprc Active Member

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                  So out of curiosity, would it make more sense to get an A body rear on there instead of changing the wheels out or should I keep what is already in there? When I get home I will get the numbers off the rear. I think there was something cast on there. I will start planning on new shackles this week.
                   
                • kursplat

                  kursplat FABO Gold Member FABO Gold Member

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                  just replacing the shackles will make it worse. you'll lower the car and still have the tire too far out. replace the rear end, get narrower wheels, or get 8" wheels with the proper offset
                   
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                  • Kipprc

                    Kipprc Active Member

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                    It looks like the rear end replacement would be the proper move. I am now finding out that the 8 3/4 rear end is not that easy to find for an A body. I am checking to see if there are any after market companies that produce them. I will change out that Leaf spring shackle setup at the same time. I guess I will bleed money until I get that rear tightened up.
                     
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                    • Scody21

                      Scody21 Member

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                      Cass at Dr Diff has them.

                      Mopar A-Body 8 3/4" Housing & Axle Package

                      As the other guys said it is best to change out the springs and hangers. You can look on Craigslist and such for a diff housing but are harder to find now a days and people want just as much as a new one. Also be careful of putting a sway bar in the rear without one in the front as this causes under/over steer and changes how the car handles and could mke it easier to spin..
                       
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                      • Scody21

                        Scody21 Member

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                        Also once you know the size of the rear housing in the car now, you could sell it to recoup your money, so it would not cost you much in the long run..
                         
                      • Kipprc

                        Kipprc Active Member

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                        Thank you sir. Everything is going on a sticky note on my wall. Got to get this fixed up right.
                         
                      • 72bluNblu

                        72bluNblu FABO Gold Member FABO Gold Member

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                        I don't think replacing the rear axle is the easiest thing to do. It would be a lot less expensive to order a set of wheels with a custom backspace to fit that rear axle. A-body 8 3/4's are not that easy to come by, and they're really expensive compared to other body styles.

                        You could also have the rear axle you have shortened, but that would mean new axles in addition to the cost of modifying the rear axle. I think the custom backspace on the wheels would be cheaper.

                        So my recommendation would be to figure out the backspace you need and order new wheels. Just based on your picture I would bet you have a 68-70 B body 8 3/4. If that's the case, you'd need 15x8's with close to 6" of backspace. Measure the distance from the spring to the widest part of the sidewall on the tire. Figure you need at least a 1/2" of clearance to the spring, and take the difference and add it to the backspacing of the wheels. It looks like you have a couple inches there, but pictures can be deceiving.
                         
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                        • Kipprc

                          Kipprc Active Member

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                          I appreciate the info. Is there anybody that the forum uses or that you wouldn't mind suggesting? I think replacing the rear is a dead end mission for me. I can't find one in stock anywhere. I am almost certain this is not an A body rear. After all the research this has to be a couple of inches too long. The Wheels would probably cost as much as the rear at this point. I will do what you suggested and start calling folks to see if they can make the rallye wheel in the size I need. There are several inches in there before the wheel or tire would touch anything, but I still want to pull that tire inside of the fender.
                           
                        • Kipprc

                          Kipprc Active Member

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                          So if I keep the rear end should I go B body specific shocks and leaf springs or are they interchangeable?
                           
                        • Professor Fate

                          Professor Fate Push the button, Max...

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                          Stay with A body stuff, B body leaf springs are completely different dimensions.
                           
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                          • Demonracer

                            Demonracer 71 Demon 00 Ram 16 Chrysler 300S 05 Caravan FABO Gold Member

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                            You will need A body springs, the B body springs will be too long. A body springs 55" long, B body 58" long.
                             
                          • kursplat

                            kursplat FABO Gold Member FABO Gold Member

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                            • Demonracer

                              Demonracer 71 Demon 00 Ram 16 Chrysler 300S 05 Caravan FABO Gold Member

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                              Wheel Vintiques offers a 15x6" wheel with 4" back spacing. they are 5 lugs with a 4 1/2" bolt circle.
                               
                            • Oldmanmopar

                              Oldmanmopar Going left turning right FABO Gold Member

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                              It looks like you have the same wheels as my orange car from looking at the pics of your welcome aboard thread Big bolt pattern. I am not positive but it looks like you have a B-body rear in the car. You will need to get the total width drum to drum and see what rear is in the car. One thing to remember is if you have Big bolt axles in the car with a duster rear. It will be 3/4 inch wider

                              All measurements are from drum to drum: Sorted by length
                              1966-1972 A-body 57-1/8″ (what your car should be)
                              1962-1963 B-body 58-1/2″
                              1964-1967 B-body 59-1/2″
                              1970-1971 Imperial 59-3/4″
                              1968-1970 B-body 60-1/8″
                              1970-1974 E-body 61-5/8″
                              1965-1969 C-body and 1965-1970 A100 Vans 61-3/4″
                              1965-1966 Imperial 62″
                              1967-1969 Imperial 62-5/16″
                              1970-1971 C-body and 1971-1974 B-body 63″
                              1965-1971 D100 pickup 64″
                              1969 C-body wagon and 1971-1973 B-body wagon 64-3/8″
                              1970-1973 C-body and 1972-1974 D100 pickup 64-3/8
                               
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