Torsion Bar Dilema

Technical advice Q&A

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Markyd
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Joined: Thu Jun 07, 2018 6:17 am
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#1 Torsion Bar Dilema

Post by Markyd » Thu Jun 07, 2018 6:38 am

The scenario;

Full nut and bolt restoration of a series 2, 2+2 over many years is now almost complete.
  • Front ride height was set as per the manual.
  • Sagged to approx 3" lower than it should be.
  • Reset ride height by rotating 1 entire spline on the rear which resulted in it being spot on (after rolling the car back and forth etc).
  • over the course of the week or so that has followed it has sagged again, by a not insignificant 1.5" this time.
The dilema is that we can't be sure the torsion bars have gone back on the right sides. There are no obvious factory markings on the ends of the bars and we didn't mark them when removing them (having never worked with torsion bar suspension before it didn't seem like the 'must' that in hindsight I think it should have been).

I'm wondering if what we are seeing is the 'set' the bar took on over their life unwinding as a result of them now being fitted on the wrong side, hence the repeated adjustment to the correct height and subsequent sagging again.

So the questions;
  • Will we see them fail as a result of now seeing them stressed in the opposite direction?
  • If they aren't about to fail, I assume this repeated sagging will shortly slow and then stop as they take on a new 'set' in the opposite direction?
  • Is it too late to swap them around and hope the original 'set' is still there and hasn't been unwound? Although as i said at the start, I don't know that they are the wrong way around at the moment even though I suspect that they are.
I'm sure forking out for new torsion bars is the safest option, but I'd rather go this route if I'm needlessly scaring myself.

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mgcjag
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#2 Re: Torsion Bar Dilema

Post by mgcjag » Thu Jun 07, 2018 7:47 am

Hi...Welcom to the forum....Whats your name.......please try to put it in the signature area along with your car model......Unfortunatly i think its one of those things that your not going to get a definitive answer to......I have never heard of torsion bars completely failing.......but then to drop 3in i have also not heard of ............however there no problem in swapping them around and trying to find a position in which they work....you may be lucky...are you positive that they were set up correctly....did you use setting links..... you will find this link very usefull viewtopic.php?f=4&t=8071 .... Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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ETTony
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#3 Re: Torsion Bar Dilema

Post by ETTony » Thu Jun 07, 2018 8:16 am

Recently I have also reset my torsion bars. I my case they are clearly marked L & R.
A year ago I set them using links, but over the summer the car settled over 2". Looked very obvious.
I reset them with the lower wishbone pulled fully down :wow: of course it was riding high now.
Then after 500 miles they had settled to bang on the correct height. No more grounding the overiders.
At £450 for a new set its a no brainer.
Tony in Devon
1967 Series 1, 4.2, OTS, RHD, Black.

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christopher storey
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#4 Re: Torsion Bar Dilema

Post by christopher storey » Thu Jun 07, 2018 6:40 pm

I would lay short odds on the problem being that the torsion bars have been transposed from L to R and vice versa

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Maikel
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#5 Re: Torsion Bar Dilema

Post by Maikel » Sat Jun 16, 2018 8:52 pm

Have been through the same story a month ago.
Resetting the bars to even 1 cm more than what Jaguar recommends in their manual.
After 50 miles it was again 1 inch too low again.
Swapped the bars from left to right as I was thinking I mixed them but then the front was 3 inch too low.

In the end I mounted a pair of other bars and since then it is spot on.

Next car I will install new bars right from the beginning.
It is a 2 hours job setting or replacing them. When you have some practice it is just hours of screwing and screwing.

Let me know how it goes but swapping sides is just a waste of time.

Maikel

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