Technical Sway bar material question

I've looked all around the net and there is no clear answer. Here's the question.
Will a sway bar made out of common cold rolled steel work, and work for a long time?
If not, what material should be used?
Thanks

 

It is not so much just what they are made out of, but that AND the fact that they are heat treated.

4130 and 4340 are common materials.

What ya' putting it in?

 

I would like to whip up a small one for the rear of my '34 that's going together

 

100% NO on mild steel.

 

Paul and his crew make excellent stuff: https://www.welderseries.com/blog/online-store/sway-bar-kit/

 

spring steel, same as springs, mild will work harden and snap

 

Heat treated SAE 5160 steel has been the standard material for sway bars for about the last 60 years.

Will your 34 have a front sway bar? If not, adding one to the rear only will cause oversteer that can turn the car into a real deathtrap. A front sway bar makes cars tend to understeer, and adding a rear bar brings the car back toward neutral steering while increasing overall roll stiffness. But a rear bar by itself isn't a good idea.

 

I seem to recall reading a textbook on this subject, by Milliken I think, that stated the opposite effect. As I remember, it stated that stiffening the front induced oversteer and stiffening the rear induced understeer.

That doesn't answer the OP's question about material, but is worth knowing if one is planning suspension setup.

Ray

 

Rear bar only will probably induce oversteer ("drift"), stiffer front will cause understeer.
The details depend on the overall setup.
Sway bar MUST be made of heat treated spring steel of some sort, regular mild steel will simply twist, bend, and ultimately fail.

 

Nope. More (or only) rear bar means more oversteer (hangs tail out, wants to swap ends in corners).

 

You would be correct Hnstray.

 

Back in the 70's, I made a set on a Datsun roadster from a material called Stressproof. Had to order it from the local dealer in Seattle. There was a procedure when heating and bending so it would not lose it's temper. Don't recall the type other than the name.

 

Buy a splined bar from Sander, buy some matching arms. Done.
http://www.sanderengineering.com/torsionbars.html

 

You can also use chrome moly tube

 

Thanks for all the replies. I didn't think common cold rolled would hold up. I know kits are out there, but I like making stuff in house when I can. Chromoly or a store bought might be the way to go.

 

You might be able to make something using a factory torsion bar, but getting the length and diameter of the bar plus arm length all to work together will be more trouble than it would be worth. I'd go with an aftermarket bar or kit.
It is also possible to change rear roll characteristics with a panhard bar, this is how NASCAR does it.

 

Local fab shop made me one out of Stressproof 9 years ago. It is still in the car and working fine.

 

You can buy heat treated bar 4140 or 4340 from Mcmaster-carr. I t will work fine. Spline the ends.
A rear bar on a 34 Ford won't turn it into a death trap. I have a 3/4" 4340 bar on the rear of my 32 Ford. I disconnected it and drove it. It wanted to push too bad. Much better with a rear bar. Stiffen the rear reduces under steer.

 

Good info ago, thanks.

 

I have used mild steel in various cars for 25 years. Mild steel has the same stifness as any other steel. It just can not take as much load as a heat treated steel. If the design is done so the loads are low, mild steel works just fine. I have one on my roadster now. It is 7/8 "steel with 9"arms welded on.

 

I don't know what they are made of but they are hard as Hell.Milled one using carbide cutter and sparks came off
it when milled

 

No, adding a rear bar, where there is no front bar, or stiffening a rear bar will increase the likelihood of oversteer.

I ain't guessing, or googling.

 

http://www.speeddirect.com/index.php/tech-info/suspension-handling-information/anti-sway-bars

 

Be carefull....even "store bought" can be cheap.."non-spring" material.
I've been chased out of booths for asking "manufacturers" what their bars were made of...!

Best to ask. Most any normal material in the 4xxx or 5xxx series of materials will work well. They also need to be heat treated to finish the process.

Mike

 

I concur with that gimpy, and I too am speaking from practical experience rather than guesswork or Google!

 

If you stiffen the rear you decrease understeer. You don't go flying into oversteer. You tune the understeer out depending how much you stiffen the rear. Adding a rear bar can make a vehicle handle better or worse depending how it is presently handling. Most vehicles understeer (heavy motor in front). You can't lump all cars under the same condition. Again adding a moderate rear bar without a front bar won't make a 34 Ford into a monster.

 

When you find the correct steel, don't attempt to save a few bucks by buying cheap rod ends. The setup used on each end of a 4-bar works really well, and doesn't cost a fortune.

 

Much as I like 'makin' stuff', springs and sway-bars seem a little out there. To that end I hie toward what the Old Timers did, and look for donor cars. With all the pick-your-own parts places now in existence, I'd get me a notebook, pencil and tape measure and spend some quality time under my car and take measurements of everything that seemed relevant and head out on the treasure hunt. As for mounting it, there are catalogs full of poly parts, Heims joints and clevises, and whatever else you might need. As to front, or rear, or both. My wife's nickname for me is "Industrial Strength". I'd add both, as well as Panhard bars, and one of those VW steering shocks on the tie-rod to reduce those forces, as well. But, then again, not everyone thinks like I do. I want my ride to hold the road like a whiskey hauler with sixteen cars of Revenuers behind it on a hare and hounds through Freedom Hills.

 

I am very interested in this subject, and have noticed many commenting on what the bar will do. No one is offering an opinion as to the need for sway bars on I beam front solid axle rear cars such as the 32-34 fords, opinions ?


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As I stated on other posts. My three 32 Fords I built all with solid axles. I tried them all with and without a rear bar. And It is better with a rear bar.