Lotus Elan

Wishbone bushes - fit problem

PostPost by: jono » Mon May 24, 2021 10:53 am

As part of the full restoration I am carrying out on my 68 Plus 2, I am now dealing with the suspension.

I bought new lower front bones from Sue Miller as the originals were poor however the uppers were okay so I shot blasted them a pressed out the old bushes.

I've gone to fit the new bushes in the uppers and there is no interfence fit - they almost drop in.

I don't know if the bushes are out of spec or the bones lost some metal when the old bushes were pressed out however this is an unexpected turn either way.

Has anyone else come across this and how did you resolve it?

I'm guessing that sleeving the bones is the only way forward but that's likely to be something of a ball ache.

Cheers

Jon
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PostPost by: richardcox_lotus » Mon May 24, 2021 12:08 pm

I replaced my front suspension bushes over the new year and got the replacements from SJ sportscars. They fitted fine, but I don’t know if Sue uses the same base supplier.

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PostPost by: elanner » Mon May 24, 2021 1:46 pm

Given enough bush changes the wishbone bush tube can stretch and lose the interference fit. I had one do this a few years ago. The simplest solution is to get a new wishbone. As you say, sleeving the bones sounds tedious.

In a pinch I've heard of people tack welding the bush into place. No doubt this would be the last time the wishbone received a new bush but it could presumably last for many years.

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PostPost by: Lotusian » Mon May 24, 2021 1:59 pm

Sue sells Superflex polyurethane bushes which should overcome this problem.
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PostPost by: snowyelan » Mon May 24, 2021 3:04 pm

Could be an issue with the bushings being out of spec....seems an unlikely coincident, see the thread below.

viewtopic.php?f=51&t=49121
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PostPost by: jono » Mon May 24, 2021 3:27 pm

Thanks for the comments chaps.

I am pretty sure that this is the first time the bushes have been replaced - the car is low mileage. The old ones were very tight - used a 15T hydraulic press to remove them so I'm not persuaded that all 4 have been stretched or lost metal by repeated bush replacements

All 4 bones are affected to roughly the same extent so I am leaning to the bushes being out of spec - they measure about the same as the bore of the housing rather than being slightly oversized. I spoke with Sue this afternoon and she has never heard of this happening before.

I would be very interested if anyone has any NOS bushes if they could take a measurement with a vernier caliper and post it up?

Cheers

Jon
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PostPost by: Billelan » Mon May 24, 2021 4:11 pm

I have a set of old new stock Metalastic bushes for my Elan S4 front wishbones.
These were purchased some 20+ years ago from a Lotus dealer so should be correct..
I have measured the outer diameter at 1.066" or 27.08mm using a micrometer.
Hope this helps.
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PostPost by: Mazzini » Mon May 24, 2021 4:39 pm

The dimensions of the steel sleeve varies from supplier to supplier.

I've tried bushes from Tony Ingrams, Sue Miller and SJ, from memory the SJ ones fitted the best.

I think the wishbones that Sue supplies are too tight, which doen't help.
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PostPost by: RichardHawkins » Mon May 24, 2021 6:34 pm

Jon,

Are you able to measure the old bush and compare to the new bush? This might help you. I hope you kept the old bush. I was given some advice by a more knowledgeable Lotus owner “don’t throw anything away” the reason being, that although the old item is worn out it may be able to to provide dimensional data to compare with the new item. Too many new items are very poor. I received this advice part way through my restoration and now keep all the old bits.

Hope this helps,

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PostPost by: Craven » Mon May 24, 2021 7:26 pm

NOS from 1980’s 27.06mm, via micrometer. brand name CLAYFLEX.
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PostPost by: jono » Tue May 25, 2021 12:04 pm

Thanks for all the comments guys.

I've checked the bushes and the tube - I don't have a micrometer but have a Mitotoyo vernier and this shows the bush dia to be 27mm dead and the tube exectly the same.

So it would appear from posts above that the bush is around 3 thou too slack - would 3 thou be a typical interference fit for this sort of bush?

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PostPost by: Billelan » Tue May 25, 2021 5:12 pm

Hi Jon.
Yes 3 thou would be a typical interference for a thin walled bonded bush. The interference is beneficial in 2 ways. A) Secures the bush in the bore thus preventing turning in the wishbone. B) Improves the fatigue (service) life of the bush.
You can't risk the bush turning in the wishbone so I would look for some bushes with the correct fit.
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PostPost by: Emma-Knight » Wed May 26, 2021 8:28 am

In my memories of old production times, we had a charge of guide pins which fell out of their housings. It showed the galvanisation had become thinner and so the tolerance went out of bounds

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PostPost by: 69S4 » Wed May 26, 2021 5:24 pm

jono wrote:So it would appear from posts above that the bush is around 3 thou too slack - would 3 thou be a typical interference fit for this sort of bush?

Jon



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PostPost by: jono » Sat May 29, 2021 5:33 pm

Problem solved!

I cut the ends longitudinally with a hacksaw (1.0mm), clamped them up to close the holes then tigged them up. A tickle with an adjustable reamer and the bushes were a nice press fit :D
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