Lotus Elan

Vibration in rear of car

PostPost by: Sea Ranch » Sat Jul 16, 2016 6:11 pm

Torsion bar?

Anti roll bar/sway bar, perhaps?
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PostPost by: Daugaard » Sun Jul 17, 2016 12:45 pm

Anti roll bar. My mistake. :oops:
English not my frist language.
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PostPost by: richard » Fri Jul 22, 2016 12:26 am

Jens... "Found it came from a worn bearing housing in the rear left strut.
The bearing could just slip around ind the housing."

I just grabbed my manual for a description of "strut". Are you referring to the entire shock absorber/ wheel bearing unit, or just the shock absorber? When you said you replaced the "bearing", are you talking about the wheel bearing? I would think that if a wheel bearing was bad it would grind, or make a noise, like what happened to my prior Elan? Sounded like I had stones rattling around in the rear suspension.

The reason I'm looking for more specificity, is that I had new bearings installed in my current +2. Of course it doesn't meant they were installed properly, but the reason I'm asking is that I have a disconcerting "thump" whenever I go over any bumps, which makes me thing something is loose.

New shock absorbers were installed, I may have to look at the installation again.

Based on the conversations so far, I'm looking first at the differential, then the rear suspension assembly, which includes the Chapman strut.

It is almost looking like there is a harmonic imbalance, unique to these cars, which exhibits itself at a specific speed. This could be caused by many things, not just a rotational imbalance.

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PostPost by: Daugaard » Fri Jul 22, 2016 7:55 am

I replaced the complet strut and the bearing. The strut because the Po had tried to gule the bearing in placeret with no luck, and I allso chance the bearing just in case.
Aften that the vibration stoppe and I am pretty sure it was the smalle jittering from the slippering bearing that got amplified throu the suspension. Did not notice any noice from the rear.
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PostPost by: rgh0 » Fri Jul 22, 2016 10:59 am

richard wrote:s that I have a disconcerting "thump" whenever I go over any bumps, which makes me thing something is loose.

New shock absorbers were installed, I may have to look at the installation again.


Richard


A thump over bumps is often a shock not clamped tight in the strut tube

cheers
Rohan
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PostPost by: jono » Fri Jul 22, 2016 12:36 pm

..I had exactly the 'clunk' you describe when going over a bump.

It turned out the bearing had spun on the hub shaft and the shaft was slopping about in the inner race.

took it out, had it welded and turned back to size, new bearings and no further issues.

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PostPost by: Sea Ranch » Fri Jul 22, 2016 7:05 pm

Whoa . . . had the axle stub welded?
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PostPost by: jono » Sun Jul 24, 2016 9:17 am

Yep,.... and the wheel hasn't fallen off in over 3,000 miles since :D

I was aware of the risks but took a punt and all is well.
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PostPost by: david.g.chapman » Mon Jul 25, 2016 6:19 pm

If the vibration could be felt only through the steering whel then I would suspect the front wheels being either out of balance or with sidnificant lateral run-out (side to side wobble). Anything more than about 1mm and it could cause trouble in my limited experience.

In your case it seems that the rear wheels or driveline are causing the issue. If you hav'nt done so already look at the rear wheels for lateral wobble. Otherwise I would look at play in anything that rotates in the driveline, or a tell-tale rectangle on the propshaft where the balance weight has fallen off! Backlash in the diff should not cause a vibration. Play in the propshaft U/Js will of course.

Best of luck.

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