Lotus Elan

Rear Strut Query

PostPost by: simonriley11 » Sun Jul 05, 2020 6:40 am

Is the steel shock absorber tube which is shrunk into the rear strut casting in one piece i.e. is the steel 'cap' which protrudes at the bottom of the strut assembly part of the thin walled steel tube which is at the top of the strut assembly. I have never taken one of these apart and I couldn't find any photos on the internet.
Thanks in advance for any help you can give
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PostPost by: gjz30075 » Sun Jul 05, 2020 9:23 am

Following....
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PostPost by: vincereynard » Sun Jul 05, 2020 1:36 pm

The tube that is visible is just a single tube with an internal thread at the top. The bottom being capped by a separate bit. The damper fits inside and is held in place by a special nut that threads on to the tube.

FYI The recommendation is that when the damper has been fitted but before fitting the nut, to fill the space with ATF or similar to transmit heat.

You can see the top of the damper inside the tube -
1277 Jul. 05 14.32.jpg and
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PostPost by: gjz30075 » Sun Jul 05, 2020 3:00 pm

So, the only way to get the tube out of the casting is to pull it out? With, of course, heating the casting..
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PostPost by: simonriley11 » Sun Jul 05, 2020 3:13 pm

Hi Vince
Thanks for your feedback. The reason I'm asking the question is that I recently fitted some new Koni inserts and after about 100 miles there was a knocking noise from the OSR strut on rebound. I traced this to the Koni insert being loose in the strut housing. I tightened up the top collar and the insert is now tight in the strut housing. My concern is that I am normally very thorough in checking (and double checking) the tightness of everything. I therefore wondered if the lower 'cap' is seperate to the shock absorber tube (as you describe) and if the bottom of the shock absorber is tightened against the inside of the cap then the 'cap' has moved downwards allowing the shock absorber insert to become loose.
Is the 'cap' just a cover or does it have the bottom of the shock absorber insert tightened against it?
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PostPost by: vincereynard » Sun Jul 05, 2020 5:28 pm

The strut tube is just that - a tube. The bottom cap is in contact with the damper. However it should be possible to see if it has moved by bright metal being visible? The bottom (internal) is generally full of crud when the old insert is removed. Are you sure there was not some still left that has now dispersed / moved and allowing the new insert to become loose?
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PostPost by: simonriley11 » Mon Jul 06, 2020 7:23 am

Thanks for the feedback and yes it's quite possible that there was some crud in the bottom - I certainly didn't attempt to clean it out when I fitted the new struts.
I'm going to take some comparative measurements with the NSR to see what differences there are between the two.
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PostPost by: nmauduit » Mon Jul 06, 2020 12:15 pm

It is possible that there had been a locating/shock eight compensator ring/washer of sort (possibly nylon) that was not exactly in place and has self-centered after a few miles, the bottom having a divot but not all shocks having the corresponding protrusion.
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PostPost by: simonriley11 » Tue Jul 07, 2020 3:40 pm

I have jacked up the rear of the car and have found the following (remember it was the OSR which was at fault):-

There is no visible evidence of the 'cap' on the OSR having moved downwards relative to the strut casting
The 'cap' on the OSR is 5mm lower relative to the bottom of the strut casting than that of the NSR
The gap between the underside of the threaded S/ABS locking collar and the top of the steel S/ABS tube is the same on both sides - circa 3mm.

My conclusion is that the steel S/ABS tube and 'cap' assembly on the OSR has previously been fitted some 5mm lower than the NSR - this doesn't matter as it just means that the OSR will have 5mm less droop than the NSR.
The play I found in the OSR was due to either me not tightening it correctly or there was some crud/spacer in the bottom of the tube which has now been crushed on re-tightening.

Gents - thanks for all your help.
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