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Front torsion arm - wear limit

Discussion in 'Steering, brakes & Suspension' started by steve_4802, Jan 7, 2017.

  1. steve_4802

    steve_4802 Active Member

    Messages:
    271
    Location:
    Sunshine Coast
    Finally got the front end completely apart and found a couple of interesting things, including cracked torsion leaves; bit of a bummer as all i planned to do was rebuild the brakes calipers and replace the ball joints. But what I'd appreciate input on is related to the torsion arms which I've found to show considerable wear at the location of the inner bushing.

    I've attached four images of a typical torsion arm. The first is from the top and shows little wear - great! But the last three are taken of the underside and show considerable wear at the inner bushing location. Funnily the outer bushing seems to be wearing very well with it still being very clean and smooth. I note Bentley states the inner bushings are usually a low wear item, but then who knows jow many k's any of these kombis have done.

    I would have thought this is a sign I need to replace the torsion arms and change out the inner bushing and outer needle bearings as well. The problems of course being, you can't buy new torsion arms and the bearings are a giant pain to replace without specific pulling and install tools. Or perhaps I'm jumping the gun?

    Am I right that the arms are shot, or would they and the bearings still be ok for a fair while and I can just put back together pleading ignorance? Or are they at a stage that I should try to source replacement arms and go through the pain of replacing the needle bearings and inner bushing now, particularly as I've come this far.

    Any tips on where I could source used torsion arms in good condition, and also tools to pull and install the new needle bearings and bushings? Do I need to get a machine shop to fabricate tools required?
     

    Attached Files:

    Last edited: Jan 7, 2017
  2. rstucke

    rstucke Well-Known Member

    Messages:
    622
    Location:
    Wamberal NSW AUS
  3. steve_4802

    steve_4802 Active Member

    Messages:
    271
    Location:
    Sunshine Coast
    Rstucke, I spotted that post before, it's extremely helpful!

    To quote yourself, "surely this auspension doesn't last forever". In light of that, in time, passable second hand arms will become near impossible to find, right? This got me thinking about a way to do away with finding another set of arms and working with what I have already. Particularly, from an engineering point of view, is it possible to machine down the existing arms, only far enough to remove the burs and get a good smooth bearing finish again? Then manufacture oversized custom bearings with inner ID to suit the slightly reduced OD of the torsion arms.

    The advantage of the above would be essentially as new bearing surface on the current arms, better than another part worn set of arms that just further accelerate the wear on the new bushing. The removal would be marginal and wouldn't result in loss of strength of the arm as you'd only go as deep as the deepest groove (already the weakest point).

    Buuut, can the torsion arms be machined down as I suggest? I originally thought, just chuck it on a lathe, easy, but then it dawned on me the out of balance of the torsion arm and I'm not sure if there is a way to get it on a lathe? Or is this not a problem; i've no experience with machining. Otherwise, could it be done with some sort of drill press or something else? I'm very blazay with metal work and machining capability so not sure what can be achieved.

    If there is a way to shave down the inner bushing location on the torsion arms then I'm very keen on the idea, when paired with custom turned replacement bushings. Be as good as new!
     
    Last edited: Jan 8, 2017
  4. rstucke

    rstucke Well-Known Member

    Messages:
    622
    Location:
    Wamberal NSW AUS
    Some thinking outside the box
    Give me some time to check this out as I may have the gear to do this.
    I have never liked the plastic bush arangement of the inner bush and if the trailing arms were machined then they can be machined again.
    Rick
     
  5. steve_4802

    steve_4802 Active Member

    Messages:
    271
    Location:
    Sunshine Coast
    Fantastic, I look forward to your further thoughts.

    I note the cip1 bushing is stated to be 2.25mm thick. Another similar idea would be a thin sleeve of, say, 1mm thick driven into the existing arms, then using a reduced 1.25mm thick bushing. Would need to be mindful of reduced wear limit and I'm not sure if bushings can be strong enough to be driven into position this thin, and also stable once thereand won't potentially break up once partially worn. But if so it would be an easier change of the sleeve along with the bushing next time around.

    I still think machining the torsion arm is a better idea and, importantly, remains consistent with the original design. But if it's not possible then thin sleeving might be another option...

    Steve
     
  6. rstucke

    rstucke Well-Known Member

    Messages:
    622
    Location:
    Wamberal NSW AUS
    The original (and cip1 bushes) were Teflon coated sitting on a plastic former inside the beam. If the trailing arms can be machined then the bushes and plastic former need to go and be replaced by bronze which I think I have.
    I'll check it out tomorrow.
     
  7. rstucke

    rstucke Well-Known Member

    Messages:
    622
    Location:
    Wamberal NSW AUS
    Ok
    You'll need access to a machine shop that has a lathe with a min 250mm swing over the bed (large lathe)
    the torsion arms will need the end caps removed and be held between centres with a drive lug.
    The machine shop should have access to bronze hollow bar large enough to make the bushes which will be thicker than STD depending how much material is removed from the arms. They will also need the beam to obtain the correct press fit to either the plastic inserts in the beam or if these have been removed the steel tubes of the beam.
    Removing the plastic inserts has risk attached. The Bentley manual states that if these inserts are disturbed then the beam becomes unserviceable. I think the inserts are there because the steel tubes of the beam are not perfectly round and they take up some of the distortion. Making thicker bushes and driving them directly into the steel tubes has advantages in that the arrangement is more solid and the bushes can be made wider (the STD bush is 20mm but the arm bearing area is 50mm wide).
    The risk is in installing the larger bushes. They have to be drive in a long way and may jam or distort and then not allow the arm to enter the bush but this should be able to be rectified by a suitable hone.
     
    steve_4802 likes this.
  8. steve_4802

    steve_4802 Active Member

    Messages:
    271
    Location:
    Sunshine Coast
    That's most helpful Rick. I have Tuesday's off work so will see if I can find some time to drive around and visit a machine shop to discuss. You're thinking is a better and more detailed description of what I was hoping to do, so I feel pretty good about the idea now.

    I had similar thoughts about the existing plastic inserts. I expected they were there to avoid potential damage driving the bushings so far in. Regardless for reason, I'll do my best to not disturb them when pulling, and use a bushing OD identical to the standard bushing.

    I'm still a little unclear regarding what you mean by removing the end caps. Can you perhaps clarify with a markup up photo of a torsion arm? Will help me describe what's required when discussing with machine shop. Thanks a bunch mate!

    Steve
     
  9. rstucke

    rstucke Well-Known Member

    Messages:
    622
    Location:
    Wamberal NSW AUS
    notice how the cap is missing and you can see the end of the torsion leaves. With the cap removed there is a short bore that is concentric to the bearing surfaces. The machine shop will be able to clean it up and turn up a centre for this end to line it up in a chuck with a drive dog.
    the other end will be in a centre in the tail stock.
    P2110090[1].jpg
     
  10. steve_4802

    steve_4802 Active Member

    Messages:
    271
    Location:
    Sunshine Coast
    Aah, I didn't spot that the ends came off. And the cap is simply driven out from the inside?
     
  11. rstucke

    rstucke Well-Known Member

    Messages:
    622
    Location:
    Wamberal NSW AUS
  12. 1500king

    1500king Well-Known Member

    Messages:
    1,532
    Location:
    Adelaide, SA
    Nice work on the replacement.!! :)

    VW have plans for the drift and disc/slide hammer set(for local manufacture) -VW771 and VW772.

    I'll scan them and post up, will help with a machinist making them quickly.
     
  13. 1500king

    1500king Well-Known Member

    Messages:
    1,532
    Location:
    Adelaide, SA
    That is exactly how we go after scrubbed arms, turn them down a touch and then make replacement inners.

    If the new bushes need a little correction after driving in, they can be reamed with VW274B (Bus front end bush reamer).
     
  14. steve_4802

    steve_4802 Active Member

    Messages:
    271
    Location:
    Sunshine Coast
    Just to close this out. Only today finally finished the front beam with a bit of a lift and redid the rear end to match ride height.

    I got carried away and didn't get photos, but wanted to encourage others to do this instead of re-installing worn torsion arms. I was told by 2 reputable VW mechanics to not bother as it's much too hard, forget you found them worn and put them back in. The main concern by mechanics was around driving out the innner bushing but it really did come out quite as it should have and exactly as described by rstucke. Definently don't worry about getting them out, just take your time and be careful you have an appropriate tool to ensure you don't drive out the plastic surrounding as well.

    My arms were moderately worn, and in the end only 0.2mm dia had to come off for it to be as good as new. I then replaced original the inner bushings with custom turned brass bushings, my new ones were same size as original new ones but with 0.2mm less ID.

    All didn't come cheap $400 for machining arms and turning up new bushings. Still, nice knowing after going that far in it's all as new.

    A big thanks to Rick (rstucke) for lending me his tools to drive out the inner bushings, saved me a heap of time and money to have my own made up by a shop, and gave me the confidence to go ahead with it.
     
    Last edited: Feb 19, 2017
    Mordred and cbus like this.
  15. AnnaBay73

    AnnaBay73 New Member

    Messages:
    29
    Location:
    Australia
    Hi, interesting post. Did the kombi drive any differently?
     
  16. steve_4802

    steve_4802 Active Member

    Messages:
    271
    Location:
    Sunshine Coast
    Not really. I still don't have the new shocks on, they should come this month.

    Until I get different shocks on there isn't really much reason it should ride differently, just hopefully not wear at the same rate. It's slightly but noticbly a little stiffer owing to the new front torsion springs, but only 10% or so. The bigger difference for me isn't the ride but now the extra lift as well that I did while I was in the front and back ends so I won't bottom out and when I do I've got bump stops there now too, which I couldn't fit in before.

    The new bilsteins should make a difference though ;)
     

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