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Urethane lower arm bushes


parrot

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For general interest. Whilst continuing the grandfathercation of my AE86, and removing various parts considered extraneous, I was finishing bolting the struts back in and noticed this.

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I’m pretty particular, and when installing them, they were lubed within an inch of their life with the supplied grease, and torqued to specification whilst on the ground, which was damn hard as it was pretty low.  Since then, it’s done about 10 kms in 10 years  

Then I had a look at the other side!

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Not good, and difficult to explain.  Fortunately at least, I noticed it, and also I was having a last look around today before putting in an Amayama order. So will be adding some standard bushes to the order

 

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Oh dear. I wonder why that happened. I suppose 10yrs is a long time juat sitting there. 

Ive never put urethane bushes in any of my cars.....until this week. 

Some whiteline  control arm bushes popped up on special  in the post xmas sales. 

I will have to minitor them. 

 

 

 

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I've had a problem with poly bushes also. I fitted SuperPro blue bushes all round, on my KE30 2 door, front & back a few years back.

I like Pete, used all the lubricant supplied.

Initially I was happy with them, & to some extent, the bushes on the front, have been pretty good.  However, my issue has been the rear ones creaking & groaning. It's bloody horrible, especially at low speed going over speed bumps in car parks etc.

If you Google noisy polly bushes, there are some classic Utube videos with audio, to make the point.

https://www.youtube.com/watch?v=QwlofW23Jyk

https://www.youtube.com/watch?v=Hl2HeNrut7s

https://www.youtube.com/watch?v=fpEZUbHVhUs

I have spoken to Fulcrum about it.  Apparently, they dry out, and that's when the creaks start. Fulcrum advised that they have now changed the design of the bush, such that it has little grooves on the inside that retain more grease.  I believe they may have also changed the grease type also. They suggested I remove the bushes & regrease them, & the problem will go away.

Apparently, there are still a lot of the old (obselete) pulley bushes being sold on-line cheap, without the grooves.  I happened to unwittingly get these.

Frankly, I'm not interested in removing & regreasing the bushes every couple of years.

I am definitely going back to the original rubber bushes, and will also be placing an order for a set of rears initially, from Amayama, although I note a complete rear set will set me back about AUD 150.00.

In the next few months, I am going to remove the springs & have them reset, so the new bushes will be fitted at that time.

I may be wrong, but the way the rubber & poly bushes work, appears to be quite different, to natural rubber ones. With the poly bushes, all friction surfaces are lubricated.  There is no lubrication with a rubber bush.  It uses a crush tube & a "squashing" action, such that the rubber in the spring actually becomes a torsional  component. Anyone who ever removed an old rubber bush from a 40 yo Rolla, can testsify that the rubber binds to the crush tube & the the spring eye.  I've even had to drill & file out, old bushes sometimes.  I thing the secret to the rubber bushes, is the quality of the rubber itself.  Despite the cost, I would not be lulled into purchasing cheap rubber bushes, of which there are plenty on line.  OEM ones hopefully are the real deal.

Like to hear any other comments regarding this. 

Cheers Banjo 

 

 

Edited by Banjo
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Over the years on the various forums there have been lots of comments about people going back to rubber, and I'm now another one to join the chorus.  At the moment, other than the control arms, I have them in the radius rods, rear swaybar, steering rack, and trailing arms.  Swaybars I'm fine with, though altezzaclub may argue that some initial give is beneficial. And I think the rigidity of a radius rod bush is desirable.  I'm a bit worried about the trailing arms though.  The rack I assume shouldn't move. 

I presume the rigidity is the problem and an expectation that the lubricant will deal with shearing forces.  But again, I'm also not interested in regularly lubricating the suspension either.  I think they gave that away in about 1938 didn't they?

Interestingly when I originally ordered the rack bush from the manufacturer 10 years ago, it was completely wrong in external shape and I had to cut it down in order to fit it (it's red).  When recently ordering D rubbers (their blue) direct from the local manufacturer for an AE86 TRD rear swaybar (they had to mill them out to suit the bar diameter) they were also completely the wrong size and shape externally.  They then had to redo them, after I measured up the bush.  I think the one they eventually used was from a Mitsubishi. 

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Its a difficult decision off the racetrack, as the endless bumps in a road or especially rallying make the wheels point in all different directions as they hit things.

But stiff bushes make a hard/noisy ride and transmit all the shock straight to the chassis mounts, cracking the steel. On the rally car I think I'll fit urethane to one end of the rear arms as the rubber tears apart, and keep the other end with some give.

The rubber mounts are formed onto the steel as a liquid under pressure, same as engine mounts, and they stick very well.

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  • 2 months later...

Got the lower arms out today. I should also add, I had these pressed in when new at a bullish nationwide suspension specialist, so that presumably doesn’t explain it.  There is no doubt the urethane is very dry and crumbles away. 

Had planned to press them out as now I have a big enough vice, but can’t find a large enough section of pipe and of course everything is shut because of Easter.....

 

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It will be interesting to see if the internal parts of the urethane have cracked like that, or if its just in the exposed ends.

It suggests to me that the urethane is formed under pressure and relaxes over the years. So it grows larger and splits when unconstrained. The bush inside the LCA might not be split at all.

Otherwise, the constant rotation must be pulling it apart along ingrained fault lines.

 

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