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Winter work - suspension

Big Les

New member
Having stripped down and overhauled the brakes last winter, it's now the suspension this winter. I've had new ARB bushes fitted (which have cured the occasional clonking at the front end) and have decided it's new shocks all round as she can be a little 'wallowy'. Standard ones will do as she's a cabby. But the question is ...whilst stripped down would it sensible to replace the springs on the front? Why would springs need replacing? And is there anything else I should consider when changing the shocks?
 
I'm not sure if it is one of those urban myths but i've always been told that springs to go 'soft' over time. Having studied Materials Science as part of my degree I don't understand how steel springs (at least a well designed and spec'd springs) can go soft over time so am sceptical of this. In fact if a springs properties do change over time and use I would have thought the opposite - that through work hardening the springs would get stiffer over time and therefore more suseptable to fatigue, although I very much doubt the springs are being compressed far enough for work hardening to occur. Therefore IMHO I would not change springs as a preventative measure (and I am a big advocate of preventative maintenance) as I don't think they wear out and undergo a performance reduction over time and use.

In preference I would replace the rubber mounts at the top of the strut as the rubber will definately degrade over time, use and exposure to oxygen.

I'm sure that by simply replacing the shocks you will get a vast improvement. I don't know why Porsche (or Sachs) made the shockers so robust that their performance degrades so much long before the shocker itself requires replacement. Remember the performance of your shock absorbers also greatly influences braking efficiency so you may very well notice a big improvement in braking as well.
 
If the springs are originals then I would recommend that you change them. They are tempered (possibly graduated) but the `rate` can change with time.

If they have `gone soft` then the damper works a bit harder to mitigate the spring rate so with new dampers you disguise the problem and will not have noticed the gentle degredation over the years. In my experience you will or should notice the difference with new dampers and springs.

It also gives you the opportunity to change the rates etc dependent upon how you drive [8D]

Me? I`ll be doing the same thing but with KW V3`s
 
Having studied Materials Science as part of my degree I don't understand how steel springs (at least a well designed and spec'd springs) can go soft over time so am sceptical of this. In fact if a springs properties do change over time and use I would have thought the opposite - that through work hardening the springs would get stiffer over time and therefore more suseptable to fatigue, although I very much doubt the springs are being compressed far enough for work hardening to occur.

Never having studied materials science I may have to bow to your knowledge.............................

but................... the springs are tempered steel I believe and the temper can be lost with work hardening and fatigue so the `rate` changes, the travel can increase which work hardens the steel/changes the temper and metal fatigue is enhanced possibly to catastrophic failure in rare cases.

I`m sure Ill be shot down in flames but over the years thats what I have learned and discussed many times [8|]
 
Sounds like it's not an urban myth then, although I still fail to understand what the mechanism for the change of spring rate is but I will bow to Hilux's knowlege and experience on this matter. If that's the case then the rear torsion bars will want replacing as well. You're basically talking about replacement of your whole suspension. It'll drive like a dream after though!!
 
You can reindex the torsion bar so it still moves within set limits, however it will have a work/life limit

They cannot be too bad though as I`ve read about people fitting coilovers and then going back to the torsion bar [8|]
 
You can have both on the rear. There is a 968cs coilover 'helper' and rear shock that can be fitted in tandem with the t-bars but I am convinced of KW's even if you don't want a really sporty version they'll have something that is much better than the old stock system.
 
Just had my front and rear shocks replaced with OEM parts by Promax last week. I am very happy with the new shocks and the car also brakes better too.

Charles
 
Thanks for all the replies!

I get the impression that if I did change the springs then I would probably need to overhaul (or even replace) the rear torsion bars, which I don't really want to get involved in. She's a cabby which is used for summer fun driving, not a 'track tool' so I think just the shocks being changed will be enough of an improvement. From what I've read I think I'll leave the springs as they are.
 

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