Lotus Elan

Front wishbones

PostPost by: Gorpon73 » Mon Jun 10, 2019 6:25 pm

Great, thanks for the info. Tightening under load makes sense. Cheers
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PostPost by: bitsobrits » Mon Jun 10, 2019 9:34 pm

Having a washer on the inside of the bushing (close to the chassis) is somewhat redundant (and adds weight :D )

In the very unlikely event the a-arm should come loose from the bushing or the bushing rubber shears, the frame would stop the A-arm from 'escaping the car', so large catastrophe is avoided.

A suitably large and strong washer on the 'outside' gives piece of mind, and might actually stop the a arm from disconnecting. But clearly not all cars have them, and their suspension is not falling off.

In an Elan, if the steering/suspension/handling feels at all wonky then check it out post haste. These cars have brilliant suspension even when somewhat 'tired', so any feeling of sloppiness, wobble, clonking, etc means you likely have a significant and possibly unsafe issue.
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PostPost by: 1owner69Elan » Mon Jun 10, 2019 9:45 pm

Data point:

Original 1969 S4 SE: NO washers on the wishbones, as delivered at the factory to me 50 years ago.
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PostPost by: Gorpon73 » Tue Jun 11, 2019 5:42 pm

Thanks again for the info. This actually got me thinking last night. Maybe overthinking this a bit....

What is actually the proper way to mount the arm on the original style rubber bush in lieu of rotational tension?

Without the washer, presumably the inner sleeve of the bush would be fixed against the nut and the arm would rotate a little on the rubber with some tension? Or does the inner sleeve actually still rotate when affixed by only the nut?

If there are washers in place, I'd presume the outer sleeve of the bush would contact the washer and be held firmly in place, restricting rotational motion? Is the best solution to use a washer with a nut that is not very tight along with a second lock nut?

Is this amount of difference in rotational tension insignificant in terms of the force/weight of the car on the suspension?

Just curious. I've only seen wishbones with washers (on the inside and outside of the bolt) in my elan experience....
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PostPost by: Craven » Tue Jun 11, 2019 7:37 pm

With this type of bush the metal parts are fixed, outer sleeve force fit to arm and inner sleeve which is slightly longer clamped between the chassis and a standard size washer and a nyloc nut. Rotational movement comes from compliance of the rubber between the inner and outer sleeves, as this is limited then the arm should be tightened in the normal ride position.
Large washer under the nut is added by some as a safety measure, as later/new bushes seem to fail in the bonding between the metal parts if this happens the arm could in theory come off the chassis.
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PostPost by: Gorpon73 » Tue Jun 11, 2019 8:13 pm

Great. So if the inner sleeve is longer, there would be no issues with using the washer.

The inner sleeve on the ones I removed appeared to be the same length as the outer, but I'm assuming its from years of being squished in there.

Thanks....
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PostPost by: elanner » Tue Jun 11, 2019 9:03 pm

The bushes can and do fail. It's not fatal, but it's alarming. See:

viewtopic.php?f=42&t=41392&start=15

As for the need for washers, as far as I can tell Elan front suspension pictures don't show them (confirmed by 1owner69Elan), but +2 pictures do. See:

viewtopic.php?f=36&t=42624

I would think that if you have original bushes, fitted without washers and not failing, then leave them alone. But if you're fitting new bushes don't blindly trust them - use washers or at the very least watch them carefully for a while until you're confident that they are of good enough quality to hold up.

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PostPost by: Gorpon73 » Tue Jun 11, 2019 10:05 pm

Yes, this is what confused me. Upon removing them (on my current and previous car) they were present.

When I referenced the manual and diagrams, none were shown.

Seems like a wise precaution assuming they do not alter the geometry of the arms or the fitment of the components at the far end....

What is the though on shimming the trunnion, ball-joint and lower damper connections at the outer end of the arm (if one is inserted on the inner end of the arm on the inside of the bolt as well). Assumed that the washer will not affect the fit enough to be necessary?
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PostPost by: miked » Wed Jun 12, 2019 8:12 am

I always check trunnion and bottom shocker fit width as i have found shocker crush tubes that are not as wide as the trunnion. Hence a shim required to prevent trapping. This trapping can put stress on the bushes causing them to shear and migrate. I would be concerned about fit if the metal outer part of a bush was migrating. Also the bone trueness. I had a big problem with front bones from a supplier were they were not accurate and migrated inboard on the top on both sides. Effectively they were clamping.
Using poly bushes i have inboard washers on my bones to allow them to bear properly.
I therefore have shim plates on the top ball joint to keep bone alignment correct.
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PostPost by: seniorchristo » Mon Jun 07, 2021 5:12 pm

Do I understand suspension wishbone operation correctly?

With original rubber bushings all movement is taken up with the flexing of rubber.
With poly bushings the movement is taken up by the rotation between metal sleeve and poly bushing.

Thanks
Chris :)
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PostPost by: miked » Mon Jun 07, 2021 8:55 pm

Yes Chris, you understand correctly. Some of the poly bushes have cross hatching in to retain grease to help maintain the movement between the crush tube and the internal part of tne bush. Since the bushes have top hats they bear side ways on the lubricated washers.
It pays divedends to take time to set up the top set on their own and also the bottom so you know you are not adding stress or friction. Then when everything is connected up, still without the shocker, you can test for nice free movement. Hence my comnents about measuing gaps to ensure correct alignment. I had some out of shape Sypder bones that were so incorrect that the old rubber style bushes migrated inboard with the amount of tension caused by tightening them up agaist the top ball joint and also the bottom of the trunnion and shocker. When put together (off the car) on the bench the gap between the bush area was much less than the chassis pivot width.
Quite a lot of people have not put the time into poly bushes and as a consequence had then locked up. Also see old posts of mine about this.
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PostPost by: jono » Mon Jun 07, 2021 8:59 pm

Chris,

You have got it in 1 :D

Original bushes act with the rubber in torsion, polybushes are akin to a 'flexible bearing' with the bushes rotating on the stainless sleeve.
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PostPost by: jono » Mon Jun 07, 2021 9:01 pm

...mike beat me to it and explained it better :D
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PostPost by: seniorchristo » Mon Jun 07, 2021 11:24 pm

Thanks Jono and Miked
I also learned much from reading your previous posts on the subject. :)
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