Lotus Elan

+2 Rear Suspension "thumps" over potholes

PostPost by: dick+2130/5 » Fri Jan 21, 2022 10:24 pm

I finished restoring a +2S 130 S in 2021, and am running it in. I last drove it regularly 30 yrs ago and have forgotten what sounds are " normal",
When I drive around our potholed estate I get a "thumping" sound from both sides of the rear suspension. Not a sound that i can reproduce by bouncing the suspension up and down by pushing on the rear wing. Does not sound or feel as if the suspension is bottoming. Not metallic.Is some sound from the rear suspension "normal" ?
Any comments from fellow owners gratefully received.
Thanks,

Dick

The dampers are replacements from SJ Sports, Lotocones from Christopher Neil, Aeon rubber buffers on the damper shafts.
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PostPost by: miked » Fri Jan 21, 2022 10:53 pm

Dick,
Are you certain the shocker inserts are retained properly in the Chapman strut. Some inserts require washers/washer in the bottom of the strut tube to pack the insert and lift it enough for the top fine thread nut to actually clamp it securely. Seen this a few times. The nut may tighten but not clamp.
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PostPost by: h20hamelan » Fri Jan 21, 2022 11:28 pm

Something is loose, probably top nut.
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PostPost by: ericbushby » Fri Jan 21, 2022 11:33 pm

As Mike says above.
I got a `clunk` sound at bumps which turned out to be a loose top nut which holds the shock absorber in the strut,
It is sometimes accessible through the spring coils to tighten it but I had to strip it down. After tightening the nut a dimple with a centre punch prevented it moving again. There should be no sound from the rear suspension. something is loose.
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PostPost by: GLB » Sat Jan 22, 2022 12:03 am

I had the problem miked refers to. Had to remove them and machine an aluminum ring seat for the bottom of the tube so the insert was held fast. About 1/4 inch thick as I recall. AVO insert. Gary
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PostPost by: snowyelan » Sat Jan 22, 2022 12:44 am

Maybe a Canadian thing, but thump is softish material colliding with something, and clunk is hard on hard. Can you clarify if the noise is metal on metal like, or if it sounds like it has a squidgy bit.
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PostPost by: alan.barker » Sat Jan 22, 2022 5:41 am

Nut holding Insert in Strut needs tightening. I had that problem on a +2. I tightened the nut job done.
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PostPost by: dick+2130/5 » Sun Jan 23, 2022 10:30 am

Hi Gents,
Thank you for your quick and very helpful replies. Good news in a way that others have experienced and fixed the same thing. I will take the spring off and check the clamping of the damper in the strut tube as suggested.
In answer to Scott (Snowyelan) the sound is like " firm rubber on firm rubber" rather than "hard on hard"
Regards,
Dick
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PostPost by: Hawksfield » Mon Jan 24, 2022 1:16 pm

Dick

_DSC4902a Lotocone.jpg and


I bought lotacones from CN in the late eighties when I had the body off, they were the type shown on the right. I believe if my memory serves me right that they were the only type available at that time.
For a lot of years i had a thumping noise from the rear that I could not identify, statically or by inspection most annoying I looked at the boot lid catch, wooden boot covers, spare wheel mounting, exhaust fixings with no succes. Some years later (late 2020)I was removing n/s suspension strut to replace bearings and noticed that the lotacone showed signs of resting on the outer rubber and was a non standard mount. at that point I realised where the thumping
came from. see image, dont know why it is upside down

20201016_114751B.jpg and
Notice rust marks on right hand mount removed
Last edited by Hawksfield on Mon Jan 24, 2022 6:22 pm, edited 2 times in total.
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PostPost by: snowyelan » Mon Jan 24, 2022 2:00 pm

I'd have a look at the diff mounts and diff clearance to the chassis.
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PostPost by: Lotusian » Mon Jan 24, 2022 7:37 pm

‘Hawksfield’ mentioned that he checked his spare wheel mount.
Have you checked that yours is good and tight, and the battery too?
The battery in one of my non-Elans was loose and made a thumping noise over big bumps.
Have you got any loose tools under the boot boards by the spare or the battery?
Did you replace all the suspension bushes when you restored the car?
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PostPost by: dick+2130/5 » Sat Feb 12, 2022 10:55 pm

Reply to Hawksfield. Thank you for your helpful words and photos. I am pleased/relieved to say that the Lotocones that I fitted are like those in your left side photo, ie they have a conical seat as recommended.
I will take a look at the fit of the top spring plate against the Lotocone conical seat and if need be go for a machined washer in between to improve the seating between the Lotocone and spring plate.
Right now I'm looking for a spring compressor that does not bind up on the bottom spring plate. My Laserr Tools one does - it needs more offset between the screw rods and the spring hooks.
Thanks again,
Dick
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PostPost by: fatboyoz » Sun Feb 13, 2022 8:13 am

Hi Dick,
I have used 1” ratchet straps on the past. Just be careful.
Cheers,
Colin.






dick+2130/5 wrote:Reply to Hawksfield. Thank you for your helpful words and photos. I am pleased/relieved to say that the Lotocones that I fitted are like those in your left side photo, ie they have a conical seat as recommended.
I will take a look at the fit of the top spring plate against the Lotocone conical seat and if need be go for a machined washer in between to improve the seating between the Lotocone and spring plate.
Right now I'm looking for a spring compressor that does not bind up on the bottom spring plate. My Laserr Tools one does - it needs more offset between the screw rods and the spring hooks.
Thanks again,
Dick
'68 S4 DHC
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PostPost by: JonB » Mon Feb 14, 2022 2:02 pm

Check the rear hub bearings for play. Happened to me.
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PostPost by: alan.barker » Mon Feb 14, 2022 3:35 pm

Rear Bearings worn or Bearing worn a groove in the Shaft give you vibration when Braking. Not a thump.
Alan
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