Torsion bars broke! NE1 know the reasons?

Asking for a friend..

Are there any “known” causes for Mopar torsion bars breaking? I know it happens from time to time, I’ve read about it here.. and I always use a jackstand before I crawl under my Satellites. Anyway...

A friend had a torsion bar break in half on one side of his Mopar, and two days later the other side broke too.
He says he just eased them out of their sockets to rebuild some of the front end parts, lube things up a bit, then put them back in again.

If there’s any info how to avoid it, or what the causes are, I’d like to share it with him.

Cheers,
- Art

Same reason valve springs break. Or any other spring.

Rust and other surface damage are the most common causes. I would question him as to how he removed the bars. Did he clamp some vise grips and hammer away or...?

The only torsion bars that I have seen break have been the right bar on slant six A body cars. They are usually .83 or .85 size. I don't know if the right side is more prone to breakage due to the weight being greater on that side. I have never seen or even heard of a larger aftermarket bar breaking.
Back in my Camaro days, I'd see some 73-81 Z28s in junkyards with broken rear sway bars, sized .55. They weren't always broken but the only ones that I ever saw break were the smallest ones. The Trans Ams had bigger front and rear bars. I never saw a broken one on any of the Trans Ams.
I've never seen a broken coil spring for that matter. Plenty of bent and deformed ones though. I've seen and experienced broken leaf springs a few times.

The chances of one TB breaking are extremely slim. Worst use of a TB is to over its lifespan is to "reverse load" it, ie switch sides, steel doesn't like that. My guess, both the long term use TB's got switched and reverse loaded by accident. he should play this week's lottery nevertheless.

While I have had race torsion bars get too weak to hold up the car properly I have only had one break.

It was part of an acid dipped pair we got from Ed Hamburger many years ago. It was the right side and broke while sitting in the garage. It made quite a sound as it banged the header. My wife was in the house and it sure got her attention.

A friend had a torsion bar break in half on one side of his Mopar, and two days later the other side broke too.
He says he just eased them out of their sockets to rebuild some of the front end parts, lube things up a bit, then put them back in again.

How did he "ease them out of their sockets" ??? . . . if he used a pair of vice grips or pliers on the surface to grip and pull them . . .then he probably created a "stress" point from the pliers where they dug in to grip, and it was only up to time before it broke from that stress point . . . there are clamps for removing t bars. Sure maybe some have gotten lucky using pliers, but why take the chance ???

If he didn't, well . . . maybe rusted badly ??????

Just a thought . . .

Cheers

Mark

I had one break while sitting in the shop one day, that will for sure get your attention real quickly.
I also would suspect your friend damaged the bars when he either removed them, or when he installed them. The bars being old didn't help, and probably removing all the tension and then reapplying it didn't help either.

Broken torsion bars make great pry bars, especially if they have a point on the broken end. Gene

"The worst case of fatigue loading is the case known as fully-reversing load. One cycle of this type of fatigue loading occurs when a tensile stress of some value is applied to an unloaded part and then released, then a compressive stress of the same value is applied and released."


http://www.epi-eng.com/mechanical_engineering_basics/fatigue_in_metals.htm

They break like any other spring.Had one break on my 67 Fury that was like 71.Had another snap on my 66 Imp that was 83.They are a spring plain and simple.Had more than one coil and Tbar brought into the shop.One on my 67 I parked it went out next day and it was snapped sitting in the drive.Why people think they cant break is beyond me.Not as common as coils but they breal like Leaf springs do.Rocky

As others have said, sounds like he used vise grips on 'em.

The ONLY time I had both bars break on me within moments of each other was after I slid a car down 40 ft of guardrail (due to black ice). The rail had slid across the bars, and nicked them pretty good too. The bars didn't actually break until almost an hour later after I had gotten the car home. Sounded like two gun shots going off.

There is at least a major error in that article. I read it superficially and what they describe as fatigue bending is something completely different. Bending a paper clip back and forth causes failure not due to fatigue, but to strain hardening. Fatigue - by definition- occurs before a permanent deformation happens, so the part does not change shape at all. This is a common mistake people who think they know metallurgy are guilty very often. Amen.q

I don't consider it a major error in this context. An error maybe, and proves you read the article. But in this context of TB's, I suspect they almost never deform, they are radial limited by design application. And the paper clip is IMO a useful analogy to help one causally visualize the reverse stress issue, since few will bend a paper clip a million+ times to witness the stress reversal fatigue issue, but bending 25? times everybody should get the "clip" point.

Thank guys,
Sure, pretty much any piece of metal that is cyclically stressed over time will break, from old age, located where there's any damage from rough handling (whether a prior owner, or himself).
I bet the potential for breakage is even higher with a car that has had many prior owners, many modifications, replacements, re-modifications - there is no way of knowing what could have been done to those bars during its rough life.
Thanks again,
- Art

Broken torsion bars make great pry bars, especially if they have a point on the broken end. Gene [/quote]

I Have one for 30+ years now stored in the corner of the garage.

I have one that I used both ends as big punches, worked great a few years back when my old Meyers snow plow played the shear game with the pins rusted in tight

when used as big punches, make sure the guy swinging the BIG hammer doesn't miss when YOU are holding the TB.