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Technical Bending a sway bar

Discussion in 'Traditional Hot Rods' started by James Mundstock, Dec 26, 2018.

  1. James Mundstock
    Joined: Jun 13, 2017
    Posts: 32

    James Mundstock

    Has anyone bent a sway bar to fit in a modified front suspension? I figured you heat it cherry red to bend it but I am not sure how to cool it. If you let it cool naturally; will it soften the bar too much? If you quench it in water; does it get too hard at the area that was heated and will it crack from movement from stresses? Any response will be appreciated. Thanks.
  2. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 7,771


    I took mine to the local spring shop (Blacksmith) who did it for me. Just take your measurements or bend some 1/8" welding wire as a template for them.
    olscrounger likes this.
  3. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,053

    from Quincy, IL

    I think you concerns are justified, and oil might well be a better quench medium than water.
    Have you searched the internet for info on dealing with heating/tempering spring steel? There are heat range crayons that can be a big aide in gauging/ controlling temps, assuming you find info on the subject.
    sevenhills1952 likes this.
  4. earlymopar
    Joined: Feb 26, 2007
    Posts: 1,098


    I have but I cold-formed mine a minor amount. You can't arbitrarily make decisions on heating, and quenching unless you clearly know the alloy and grade of steel the bar is made from. Cold-forming is another story altogether and it really depends on how far you need to form it and what the current heat treated condition or state of the steel is that you're using. Stumpy's suggestion is good.

    - EM
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  5. 41rodderz
    Joined: Sep 27, 2010
    Posts: 3,579

    from Oregon

    How much does it need bent?
    Elcohaulic likes this.
  6. At the wrecking yard I've seen bent bars from collisions AKA cold forming. I think that's the only way I'd do it.
  7. Fordors
    Joined: Sep 22, 2016
    Posts: 2,468


    I imagine some sway bars are made from spring steel but plenty of them have been made from mild steel. If mild steel I think it would be safe to heat, bend to suit and then let air cool avoiding drafts.
    As a field test you might take a file and see it you can put a small nick in the bar. If the file just skates across the surface then it is a high carbon material and heating should be avoided as it will probably affect the qualities. I’m not a metallurgist and no, I didn’t stay at the Holiday Inn Express last night, JMO.
  8. Glenn S
    Joined: Jun 22, 2015
    Posts: 33

    Glenn S

    Well I bent both say bars under my Desoto over 18 years ago and neither have deformed or cracked in that time and it gets driven hard around corners. Mine were heated to an orange red colour then quenched in oil (a large volume of oil so that it doesn't heat up excessively). Also I didn't rush the heating so that there was no hot spots created that could damage the composition of the steel.
  9. Fabber McGee
    Joined: Nov 22, 2013
    Posts: 802

    Fabber McGee

    Bend it cold in a press. Same as re-arching a leaf spring. I put a rear sway bar that I was told was from a Chevelle under the rear of my 69 Torino stock car in 75. Needed to be about 6 inches shorter (narrower) at the mounting flanges. It had a big offset to get it around the differential so I just put it in a press and bent the curves to a tighter radius. Being a spring it had to be bent quite a ways past at each location, then when the press was released it would retain some of the bend. Took about an hour as I recall. It was raced in that car for several years with no issues.
    There will never be a mild steel sway bar in any car. It wouldn't last more than a few miles before fatiguing and breaking. A sway bar is a torsion spring.
  10. I bent one to fit my Nova stock car, the ends were clocked the wrong way maybe 15 degrees. One of the U-boat commanders at work (old German guy..) helped me using our biggest press, we marked the area out and worked it back and forth. The first side took about an hour, the 2nd about 1/2 of that.
  11. WZ JUNK
    Joined: Apr 20, 2001
    Posts: 1,622

    from Neosho, MO

    IMG_3579.JPG I bent the sway bar ends on my current driver. I heated it with a torch and bent the ends to the shape I needed and then I let it air cool. No problems and I have about 15,000 on it in the last couple of years. I was told that the twisting of the sway bar takes place in the middle section and the ends can be thought of as levers. So bending the ends to accommodate the shape you need, should not interfere with the twisting or spring like action of the middle section.

    I changed the bottom sway bar, so it would replace the top bar. I needed a bar that did not have the dropped center section.

    I do know this, what works for one guy, may not work for another.

    Last edited: Dec 27, 2018
  12. dwollam
    Joined: Oct 22, 2012
    Posts: 898


    40+ years ago my brother (deceased) cut the ends off of a '70 Coronet cop car sway bar to shorten it for his/my '62 Lancer. Ends were welded back on after shortening. Still on there and still working fine.

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  13. I did mine not wanting to. The car slid off the jack. :oops:
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  14. 1-SHOT
    Joined: Sep 23, 2014
    Posts: 1,623


    Believe it or not, but G.M. Had a tech sheet in the late 60's and early 70's on how to normalize a sway bar, to keep one side being lower than the other side. I worked in a Oldsmobile dealership at the time and this was a daily fix.
    We jacked up the low side to preloaded the high side then took a rosebud and heated the center of the bar about 18 in. To a dull red an let it air cool then let the car down and it would set level.
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  15. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,610


    Have bent quite a few in a press-no problems
  16. goldmountain
    Joined: Jun 12, 2016
    Posts: 1,439


  17. sdluck
    Joined: Sep 19, 2006
    Posts: 2,277


    We were racing at Fremont raceway dirt track,we had a VW super sedan,we needed a rear swaybar,the guy's next door had a wrecked caddy ,my boss removed the swaybar cut it in half and welded it together in a Z shape it never broke even when we wrecked the car
  18. 54vicky
    Joined: Dec 13, 2011
    Posts: 1,245


    we did it a lot while racing heated cherry let cool slow no problem.
  19. Mike VV
    Joined: Sep 28, 2010
    Posts: 1,734

    Mike VV
    from SoCal this thread scary..!

    Heating and letting cool slowly...the bar is all but useless, now dead weight ! Of course, you've had "no problem", no work is being done by the bar (MAYBE 10%)..! The heat treat is gone from those heated affected areas, little memory left in the material.
    Heating of the connector arms (levers !), the bar has lost 25% to 50% of its effectiveness. The percentage depends on the lever length and the heat effected area. Again, little memory left in the material.
    Mild steel bars are...well, about useless, dead weight. And again...little memory to begin with in mild steel. Without memory, you don't have much of a spring..!

    Maybe...some heat treating and metallurgy classes are in order here !

  20. Atwater Mike
    Joined: May 31, 2002
    Posts: 9,867

    Atwater Mike

    IF quenched in oil, it MUST be used oil. The carbon content is crucial.
    Hnstray likes this.
  21. saltracer219
    Joined: Sep 23, 2006
    Posts: 690


    I have no idea what a mild steel sway bar would be good for other than adding weight to the vehicle!
    gimpyshotrods likes this.
  22. Old HAMB Metallurgist here. I think most sway bars (technically they are anti-roll bars for the correct terminology, but sway bar is commonly used) are heat treated. Never have seen specs for typical composition or heat treat level. But just as heating a spring to lower a car destroys the heat treat level, it would be similar in a sway bar. Cold bending would be preferred if the change is rather small. You can use penetrant or mag particle inspection to check for cracks if concerned after the bending. Being heat treated it will have a lot of spring back, due to the higher yield strength.

    As to the ones that have heated and it still works, yes it probably does. The issue is that in extreme one wheel up and other down, you could get some permanent distortion to set in. That's due to the yield strength is now lower. If the high applied stress is in that heated area it could exceed the now lower yield strength.

    The problem with heating an area and then quenching in oil (probable due to the carbon content to avoid cracks, oil is slower than water) is that you have now introduced 3 types of microstructure: the original in the non-heated area, and overtempered soft area in the heat affected zone near the red hot region, and the overhard as-quenched heated region. In order to really do it right, you need to heat treat the whole bar again, which means quenching and then tempering to the desired strength level. Heating and air cooling will prevent cracks, but you will have non-heat treated low strength level in that heated region, kind of like the heat affected zone mentioned above.

    Cold forming will make it a bit harder and higher strength in the reformed area, but should not be any issues for long term reliability. The heated and air cooled version will be soft and susceptible to fatigue cracking, but without high miles and higher stresses it may never actually crack. OEM designers build to design levels that are beyond the normal use.

    Only other factor I can think is some newer cars use tubular bars, those would be harder to reform without crushing the tubing. Older style solid bars would be easier to cold form.
  23. blowby
    Joined: Dec 27, 2012
    Posts: 6,278

    from Nicasio Ca

    I tried to bend one to fit, basically from 45 degree ends to 90s. In a vice with a cheater pipe, cold. Took all the weight and strength I could muster. First side bent fine. Second side snapped, sending me crashing into the nearest wall. As others have said, they'll go some cold, not too much.
    loudbang and gimpyshotrods like this.
  24. Fireball Five
    Joined: Oct 5, 2018
    Posts: 55

    Fireball Five

    That seems like a strange way to cure a problem caused by something else. I bought scrap from our local dealer back then that always included lots of front coil springs from Oldsmobiles. About a 1/3 rd of a pickup box one time.
    I remember a lot of half low riders around town. Looked like they were all owned by highschool kids.
    Fireball 5

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