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> Torsion Bars, Life span ?
jim_hoyland
post Jun 5 2021, 10:29 AM
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Curious; Do torsion bars wear out ?


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mepstein
post Jun 5 2021, 10:54 AM
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I'm no expert but you need to replace if there is heavy corrosion or a wear mark from the rubber bushing failing. They do break. I just came across a broken rear torsion bar from a 911 and it was a thick one. I don't know what did it in but it wasn't pretty.

Funny thing is, a lot of them break while the car is sitting in the garage, not actually while driving. At least that's my experience.

Replacing after 50 years might be good preventative maintenance but on the other hand, there's a thousand other things that can also go wrong on our cars.
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jim_hoyland
post Jun 5 2021, 11:05 AM
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Thanks for that; how would the ride be affected from both a worn TB and a broken TB ?
Everything has been replaced or upgraded on my front end, but the ride isn’t that smooth
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mepstein
post Jun 5 2021, 11:08 AM
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Worn bar won’t change anything. Broken will be obvious. One corner will be bottomed out at rest and not really drivable.

Stiff tire sidewalls and tire pressure can make a pretty big difference.
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SirAndy
post Jun 5 2021, 12:08 PM
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QUOTE(jim_hoyland @ Jun 5 2021, 10:05 AM) *
how would the ride be affected from both a worn TB and a broken TB ?

A broken TB literally means that corner of the car is falling to the ground. It'll be sitting on top of the tire and/or strut housing. There's no way to drive the car like that.
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914Toy
post Jun 5 2021, 02:40 PM
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QUOTE(jim_hoyland @ Jun 5 2021, 10:05 AM) *

Thanks for that; how would the ride be affected from both a worn TB and a broken TB ?
Everything has been replaced or upgraded on my front end, but the ride isn’t that smooth


What diameter torsion bars did you install?
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jim_hoyland
post Jun 5 2021, 06:20 PM
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QUOTE


What diameter torsion bars did you install?


They are still the original TBs…
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windforfun
post Jun 5 2021, 07:43 PM
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Mine are almost 50 years old & all is still good. My original shocks still work fine too. I have only 48K miles on the car.

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930cabman
post Jun 7 2021, 04:57 AM
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Every motion of a torsion bar introduces stress, after how many cycles can this thing last? I am sure with quality steel these last a long time, but 1/2 century and still rolling.
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mepstein
post Jun 7 2021, 05:02 AM
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I think it’s a weak spot from corrosion or rubbing that does them in.
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jim_hoyland
post Jun 7 2021, 05:56 AM
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Can they be tested in the car ?
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Superhawk996
post Jun 7 2021, 06:00 AM
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QUOTE(mepstein @ Jun 7 2021, 07:02 AM) *

I think it’s a weak spot from corrosion or rubbing that does them in.


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Corrosion creates a stress riser. Highly stressed steel abhors a stress riser.

QUOTE(jim_hoyland @ Jun 7 2021, 07:56 AM) *

Can they be tested in the car ?


No.

They are either working or they are broken. Sag is hard to detect since the torsion bars can be adjusted so sag gets offset over time. Torsion bar is also less prone to sag than a coil spring by virtue to the shorter length of spring steel used in a torsion bar and the larger diameter of the steel.

When I took the bars out of mine, they had some serious pitting. Still were functional at the time of removal but they will not be going back into my vehicle. Too much risk of them breaking in the future. Always happens at the worst time. Time for new parts.

QUOTE(930cabman @ Jun 7 2021, 06:57 AM) *

Every motion of a torsion bar introduces stress, after how many cycles can this thing last? I am sure with quality steel these last a long time, but 1/2 century and still rolling.


Life of a spring is not measured in time.

Spring life is measured as # of cycles of full reversal between two load conditions. Would be measured on the order of # of millions of load reversals.

As noted above by Mark, corrosion, nicks, and worn in rub points resulting from from worn bushings are leading cause of death for torsion bars.
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SirAndy
post Jun 7 2021, 10:01 AM
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QUOTE(jim_hoyland @ Jun 7 2021, 04:56 AM) *

Can they be tested in the car ?

No, but they can be removed fairly easily.

Jack up the front of the car until both wheels are in the air, remove the adjuster screws to take the rest of the load off the bars, remove the adjuster cap and tap the bars out.
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930cabman
post Jun 7 2021, 12:13 PM
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@Superhawk: Exactly how it works.

All the others: Isn't it great to have an engineer on staff to get us through this
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