How big a torsion bar nick is ok?

Suspension, Steering and Chassis

  1. Backally

    Backally FABO Gold Member FABO Gold Member

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    D7ACBC0E-6D74-4FE4-AEDA-0F917CB601DE.jpeg Found a set of torsion bars in my garage. Before I sell them, how big a nick is acceptable? Can catch a fingernail on it
     
  2. 72bluNblu

    72bluNblu FABO Gold Member FABO Gold Member

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    That’s junk. Also why you never use vice grips to remove a torsion bar you want to use again.
     
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    • MoparMike1974

      MoparMike1974 FABO Gold Member FABO Gold Member

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      Smooth it out with a sander to get rid of the stress risers. Should be fine.
       
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      • qkcuda

        qkcuda Well-Known Member

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        I had a spot like that and dressed it with a file and have been running them for years.
         
      • 72bluNblu

        72bluNblu FABO Gold Member FABO Gold Member

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        Nope. That bar is garbage.

        You have to understand that the vast majority of the load on a torsion bar is carried on the surface. That’s why things like hollow sway bars work just fine and actually aren’t usually much larger in diameter to have the same rate.

        That’s a damaged 45+ year old spring, and it’s damaged in a spot that’s critical to its function.

        And how many miles? You put 50k miles on it yet?

        That bar is junk.
         
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        • jos51700

          jos51700 Green Bearing thread connoisseur

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          Properly dressed, corrosion inhibited, and safely loaded, it would be fine.

          Do you have the empirical experience to insure those things? The cost of a catastrophic failure versus the cost of a replacement bar..... not really worth it.
           
        • Backally

          Backally FABO Gold Member FABO Gold Member

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          Found them in my garage, didn't even know I had them. Cleaned them up to sell them and found this. Not going to sell them to someone if there is the possibility of them failing on someone.

          Thanks
           
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          • Daves69

            Daves69 Well-Known Member

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            Maybe take a poll on who would buy these in the as pictured condition.
             
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            • 72bluNblu

              72bluNblu FABO Gold Member FABO Gold Member

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              You mean, properly dressed, corrosion inhibited, and safely loaded, that bar would not perform as designed. There's no proper way to fix that bar that results in working the way it's supposed to.

              When you damage a bar like that with a compressive force, the metal under the damage is compressed, which also means hardened. So, even if you smooth out the nicks, you have hardened metal in those areas where stress risers will still form. So you have to go deeper than just the nicks.

              Then, you have a section of bar that's at a smaller diameter. The outer diameter of the bar is key in determining the spring rate of the bar. Just look at how much difference a few hundredths of an inch make on the rate of the bar.
              torsion_bars copy.jpg

              For the A-body bars you see .02" make a 10 lb/in difference in the rate. What will it take to clean up those nicks? Now you have a section of bar operating at a different effective rate than the rest of it. You think the overall rate of the bar is going to be the same? Do you think that the section providing less resistance than the rest of it will cause metal fatigue/stress in the area it necks down?

              Sure, if you smooth it out enough you might not get a big crack to propagate right away from the end of one of those grooves, but eventually that weakened section of bar will come back and bite you. And really, it's already a 45+ year old spring with who knows how many miles, so who knows how long it'll last.

              Toss 'em. Even in mint condition they're not worth that much.
               
            • jdsduster

              jdsduster Well-Known Member

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              wow,its good,its bad,its good ,its bad.use at your own risk.ive personally never had one break.i would buy a new one,they are not that much,that way you will know for sure its good
               
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              • Daves69

                Daves69 Well-Known Member

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                They sound like a M-80 or Silver Salute going off under your car accompanied by fast drop of the affected front side of your car.
                Be careful handling the as the broken edges will be extremely sharp.
                 
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                • OL DODGE

                  OL DODGE Well-Known Member

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                  I wouldn't use it-IMO. A lot of excellent points against using that have been made, That's what makes this website so awesome-you get educated,opinions, and real life experiences. Wish it would've been around in the 80's when I was learning the hard way!
                   
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                  • marksmopar1

                    marksmopar1 Well-Known Member

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                    My Buddy's RoadRunner was just sitting in the driveway, he was in the house and heard huge bang! When he went out to look he found his RR sitting low on one side, the damn T-Bar broke as the car was sitting! He had just returned from a ride. So these things do go bang big time when they go....I would just get new, why take the chance...sell those ones you have to those guys that think the bar is ok..let them run them ;)
                     
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                    • chryslerfat

                      chryslerfat Well-Known Member

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                      Mom and dads Fury Sport was the same way. Sitting in the garage and heard a bang went out to see what it was and the car was down on the right side.
                       
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                      • valiantwagonguy

                        valiantwagonguy Well-Known Member

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                        That bar is garbage
                         
                      • Rudy`s Ride

                        Rudy`s Ride Well-Known Member

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                        Those are great to use for horseshoe pit stakes.
                         
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                        • jos51700

                          jos51700 Green Bearing thread connoisseur

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                          My point exactly. It can be done, but it ain't worth it.
                           
                        • 72bluNblu

                          72bluNblu FABO Gold Member FABO Gold Member

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                          I think you missed my point. It can’t be done.

                          Removing enough material to remove the stress risers from the damage will create a section of bar with a different diameter. With the way a torsion bar carries load that section will operate at a different torsional rate then the rest of the bar. It might last longer than running it as is, but eventually it will break in that spot. You’re just trading a stress riser fracture for a fatigue fracture in the section of bar with a narrowed diameter.
                           
                        • SGBARRACUDA

                          SGBARRACUDA ROY FABO Gold Member

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                          Owned Mopar my whole life, never broke one. And before I knew better would use a pipe wrench to grab the bar and knock them out with a hammer when rebuilding front ends. I would stick back in and run them. Never had a failure. Maybe I was lucky? Could it fail? Maybe. Those bars are tougher than some would have you believe. In normal use they are subjected to all kinds of road hazards and debris attacking them.
                           
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                          • jos51700

                            jos51700 Green Bearing thread connoisseur

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                            It can be done. All one has to do is remove material along a significant portion of the bar. Let's face it; even the hex ends are larger than the bar diameter (well, the new bars not so much), and they don't break at the ends because the radius is large enough.

                            As I said....IF you can guarantee those three things...otherwise, not worth it.
                             
                          • oi81b4uu812b4

                            oi81b4uu812b4 Well-Known Member

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                            Old torsion bars make good pry bars!

                            So it does have a use!
                             
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                            • MRGTX

                              MRGTX Well-Known Member

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                              I follow your logic here and I think you're right. Some confusion may be coming from the instructions in shop manuals that suggest cleaning/polishing/painting scratches and nicks in the bars as the recommended procedure...but the important distinction here seems to be a matter of degrees. A scratch deep enough to alter the spring rate of the bar (and at the outer edge, it doesn't take much) is a "ticking time bar." :D

                              I get that torsion bars aren't exactly the cheapest component to replace but they're also not so expensive that anyone in the car hobby shouldn't be prepared to replace a set when necessary. Put these in the category of brake calipers, ball joints, etc... they'll typically last a long time but when they need to be replaced, it's non-negotiable.
                               
                            • Dartnut

                              Dartnut Don't hate me because i'm beautiful

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                              What's your life or someone else's worth?
                              You can buy new ones for pretty cheap...........
                              My vote is to cut it in half and use it for a pry bar etc. before someone decides it's ''good enough'' to use.
                               
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                              • mikebee

                                mikebee now's the new later...

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                                I've had one break with me sitting in the driver seat just got back from a hell ride and I'd still use that one if its a 340 bar.
                                 
                              • RustyRatRod

                                RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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                                I've run much worse......but didn't know it. Why take a chance when new bars just don't cost that much?
                                 
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