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chesney

Do Torsion Bars Wear?

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chesney

Just wondering if torsion bars loose their stiffness as they get older.

 

My 205 seems a bit bouncey even with new shocks on. It has a 309 rear beam.

 

I was begining to think I had maybe put the ARB in badly and it was unsettling the set up. Like when I come over the crest of a hill and the weight comes off the rear it seems to lift more at one side than the other.

 

I did recondition the beam myself recently and have put new stubs and bearings in it and it has no play so can't be that.

 

I have tried different ride height settings and it is always the same.

 

I'm overseas and haven't driven it in about a year but want to sort it when I get back in April! :)

 

Any ideas?

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C_W

When you say bouncy this could mean it's walloly and soft with poor shock absorbers or quite stiff and skips/bounces a bit; this may be the case with a stiffer 309 rear beam.

 

Not sure what happens to the torsion bars when they get old/worn though.

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chesney

It is more like having worn shocks or unevenly worn shocks. I drove the car with no shocks on once and it's behaving similar to that but nowhere near as extreme.

 

Think I'll try to reset everything when I get back and maybe leave the ARB disconnected to see if it has any effect.

 

Another thought is that the torsion bars are not torqued up evenly. Overtightening them can cause the swinging arm to stiffen. Maybe one is too tight

 

As a second test I'll put some other shocks on.

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perfecto pug

the torsion bars themselves shouldnt wear as the splines are a very close fit

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C_W
the torsion bars themselves shouldnt wear as the splines are a very close fit

I think he means age and become weaker rather than slacker.

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perfecto pug

hmm... i suppose it might be possible, it all depends on what forces are needed to change the properties of the sprung steel

 

any metal specialists out there??

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pacey205

I would say that its particuarly unlikely that the steel would lose any of its elacstic properties over time as the conditions it is under arent particuarly taxing. I could understand if it was under high temperature as you would experience creep but your talking high temperatures here (well over 100 degrees) so this is particuarly unlikely.

 

Of course it is under constant forces so there is going to be a good amount of cyclic torsional stresses being applied but I cant really see that it would be at a level to actually degrade the metal as it would have to breach the yield strength of the metal to have any effect on how 'elastic' it is and youd definatly notice if this was to happen. Also I doubt peugeot would have used any dimensions/compositions etc where this wouls be likely to happen as there should be a resonable safety area built in top prevent this.

 

So Id say it was unlikely that the bars would 'weaken' with age unless there was a serious application of force at some point although technically they should have been able to cope i would have thought.

 

HTH

 

Michael

 

P.S. Im certainly no specialist in this area but Im just using my basic materials knowledge here, obviously youd need to do proper testing to accurately predict the failure life of the torsion bars but I would have thought it is unlikely.

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Adi

Does a coil spring sag......course it does. So why shouldn't a torsion bar spring sag over time??? They are both made of similar spring steel. Obviously the torsion bar isn't wound like a coil spring is.

A lot will depend on how the the bars are heat treated.

 

Does anyone remember the front end of Morris Marinas??? They used torsion bars and the front used to sag badly after a few years. Engineers have found better grades of metal to use......also better methods of treating it. It just means the sagging will take longer.

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pacey205

Thats true i suppose, Im going purely on the basic material principles here though so Ive not really considered the shape. As you said alot depends upon what grades are used, treatments etc.

 

How old is the car ?

 

Michael

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niklas

I've also heard about seized torsion bars, and I guess that has with age and wear to do as well.

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C_W
I've also heard about seized torsion bars, and I guess that has with age and wear to do as well.

That won't be the torsion bar that has seized as that isn't possible; the torsion bar is a metal bar with 2 fixed end points. It will have been the trailing arm that could sieze.

 

EDIT: I reread it and of course the torsion bars can sieze! Insomuch that they can become siezed in their splined fittings when you're trying to remove them. But for normal suspension operation the torsion bar can't "seize".

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niklas

I hope you're right.. I would be quite afraid if this happened to me on the motorway :blink:

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chesney
Does a coil spring sag......course it does. So why shouldn't a torsion bar spring sag over time???

That's what I was thinking.

 

I put the 309 axle on when the car had around 80,000 miles which was about 9 years ago and it now has 207,000 miles on it. Plus I'm not sure how many miles were already on the axle.

 

The rebuild I did was just to replace the parts that wear like the bearings and bushes.

 

It was also unused for long periods. Like when I was travelling for over a year and it sat in the garage up on blocks to prevent tyre flat spots. And since I got a second car 4 years ago.

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Adi

Well the good thing about the torsion bars and sag is.......you can always raise the rear up slightly. If the bars are adjusted the right way.....you could raise up say 5mm. That would correct any sag......and if the torsion bars are still working correctly, then there will be no danger of the bump stops being hit.

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Guest pugderv

They will sag in away but they will twist and stay like that, so in theory you need to raise the suspension abit to compensate

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C_W

Perhaps if there was sagging you could maybe raise the rear back to normal ride height? :D

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Beastie
Does a coil spring sag......course it does. So why shouldn't a torsion bar spring sag over time??? They are both made of similar spring steel. Obviously the torsion bar isn't wound like a coil spring is.

Just to add to that logic (which I'd agree with :) ) torsion bars and coil springs actually work in almost identical fashions: The coil spring is just a torsion bar wound into a cylindrical shape and it provides its elasticity by twisting the spring wire in the same way that a torsion bar does.

 

I've had to replace both coil springs and torsion bars on old vehicles because they have "worn out" ie: the material is beginning to yield. This usually happens after 40 or 50 years or so :)

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Guest pug205xsmuppet

hiya peeps

 

the torsion bar is on a picture here

 

Torsion bar

 

Well Right at the end where the shocker is on the drivers side i think there called Radius arm bearings acording to a MOT man! and he said mine have worn , :)

 

So when u look at the back the one wheel is at a angle so its rubbing the ache at the top! :)

 

Does anyone know where u can get a re-con torsion bar ?? at all ?? :(

 

I know the Radius bearing wear down lol

 

Cheers

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C_W
Does anyone know where u can get a re-con torsion bar ?? at all ?? [sad.gif]

 

I know the Radius bearing wear down lol

 

Cheers

 

By re-con torsion bar I assume you mean re-con rear beam! :) If you do a search there will be plenty of threads about rear beams.

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Guest puggti

I think Perfecto Pug does them! :)

Edited by puggti

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jonnie205

xs muppet the best palce to get a beam will be the scrappy. go and get one out of a low milage pug and this will be by far the cheapest way of doing it

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Guest pug205xsmuppet

hiya :(

 

Ok cheers mate :)

 

thanks :)

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Guest pug205xsmuppet

Hi

 

Do you know how hard it is to do a torsion bar anyone? :D

I done one the other day anyone tell me ? :D

 

cheers

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Guest Sgoaty

i was going to lower the back of my 405 today and it was the first time ive payed any attention to the rear beam. It looks like the torsion bar will bend when the suspension is moved as well as twist this has me a bit confused. The only torsion bar ive delt with before was on a compressor chassis and that was completely different.

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Adi
It looks like the torsion bar will bend when the suspension is moved as well as twist

 

Yes the bar twists......thats how the spring action works. But other than that, the bars stay very straight.

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