Lotus Elan

Rear strut threaded sleeve stripped

PostPost by: Davidb » Sun Jan 31, 2016 11:02 pm

I think the title says it all-I picked up the left rear suspension assembly to move it to another spot in the garage and the threaded sleeve that holds the shock absorber in just popped out! The threads are stripped.

Is replacing the tube the only fix?
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PostPost by: tvacc » Mon Feb 01, 2016 6:05 pm

I cant think of another fix. I would take this opportunity to buy the tubes that are threaded and go to an adjustable rear suspension for ride height. Allows you to corner balance the car. Corner balancing makes a heck of difference.

I happen to have two rear bearing carriers for sale that are a little worse for wear, but usable if you really want to replace it all. Don't know where you are located.
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PostPost by: rgh0 » Mon Feb 01, 2016 7:26 pm

The tube thread is very fine and shallow. Are you sure its the tube thread that is stripped and not the cap that threads into it and clamps the shock in place?

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PostPost by: Davidb » Mon Feb 01, 2016 8:34 pm

Thanks for the responses.
I am thinking of replacing the tube and going with adjustable spring perches. How do the tubes come out-heat and pull?

Rohan, Yes the Tube and the retainer are both stripped. Judging by the amount of wear on the threads in the tube I would say it was like this for a long time-the previous owner could not have failed to notice. I bought the car as a project but still paid a good buck for it because of its racing history. I have yet to drive it...
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PostPost by: 512BB » Tue Feb 02, 2016 9:59 am

David wrote; the Tube and the retainer are both stripped

No doubt caused by the threaded retainer coming loose in service, and being used like that for some considerable time.

Much heat will be needed to remove the strut from the housing, suggest using a professional outfit to do it for you.

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PostPost by: Davidb » Tue Feb 02, 2016 7:28 pm

512BB: thanks for the response.
I am reluctant to try removing the tube. The guys in the shop I am associated with are very good welders and they are going to cut the top few inches off the tube and weld a new piece on.
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PostPost by: toomspj » Tue Feb 02, 2016 8:00 pm

It's really not a big deal to remove the tube and replace it. You just need to warm the ally housing then push tubing out using a press. It normally doesn't take much to get it moving. If your shop can cut and weld new threads on they should certainly be able to accomplish it.

Replacing the tube is slightly easier as you can warm the ally and keep the steel tube cool. I've done it many times for racing and I've never had a problem with tubes moving afterwards.

I suspect po didn't realise it had come undone else he'd have fixed it. I have worked on a number of people's active race cars and you'd be amazed at some of the things we see! Often people don't have an idea of how good a well set up a balanced Elan is to drive - they think that having to wrestle the car around is normal!

I think that would be better than the slightly bodgy approach of welding a piece on the top.


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PostPost by: tvacc » Tue Feb 02, 2016 8:09 pm

Yes, they come out real easy. What you can do is heat the aluminum. then dip the tube into a vat of ice water. Heating the carrier expands it and cooling the tube contracts it.

I actually did it myself without a press. Just a chain clamp vice grips and it spun and pulled right out.

My problems with these have always been the bottom metal cap rusting and the shock coming through the bottom.
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PostPost by: CBUEB1771 » Tue Feb 02, 2016 9:49 pm

I agree that removing the tube from the hub carrier is actually fairly easy. An oxy-fuel torch with a big heating tip helps. It is also important to clean the section of the tube inside the hub carrier before attempting removal. This will minimize scoring of the bores in the hub carrier during the removal process.
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PostPost by: Davidb » Tue Feb 02, 2016 10:50 pm

Thank you gentlemen! First I have to find a replacement tube-shouldn't be too difficult.
Properly Tig welding a new top on the tube should not be considered a "bodge" I think but if I can replace the tube...

Edit--I think now is the time for adjustable spring perches!
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PostPost by: 512BB » Wed Feb 03, 2016 11:00 am

Of course, it should be noted, that what seems like a simple job to one person, may appear daunting to another.

Different folk on here will have different skillsets, different equipment, and a may have an unsuitable area to work, and therefore may not feel that they would want to take on a particular job, no matter that another member feels the job is a simple one.

Having said that, personally I would not advocate a repair / extention to a strut . It is a safety critical area and not one that I would undertake. Better to find another insert, long time unavailable, or find a replacement good second hand unit.

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PostPost by: rgh0 » Wed Feb 03, 2016 11:38 am

TIG / MIG welding a new section of tube on the top to replace the damage thread section can certainly be done to achieve a tube section as strong or stronger than the original and no visual sign of the weld would be seen if machined back after welding. Fitting a sleeve carrying the thread for adjustable spring seats is also easy and a routine task that many have done.

I would not just replace replace the whole tube if I just wanted adjustable seats.

However welding the new tube section on requires good weld preparation and weld procedure and I would want to check it for weld quality afterward. Ideally you would do this via x-ray or ultrasonic examination which may be costly but many small private aircraft maintenance facilities have this capability relatively cheaply. The alternative is a visual examination by someone who knows what they are looking at and die penetrate crack testing which is much cheaper and easier to do. Given that a crack in this weld will not actually result in a catastrophic suspension failure says this simpler examination is probably acceptable.

When did most people last crack test in any way the critical welds and components their Elan steering suspension and brakes that are more important than welding a top on a strut ? Its not in the workshop manual to do but given the age of the cars and their marginal original design and fabrication it truly needs to be done if the cars are to be seriously driven now ( I will get of my soap box and stop my speech making now :lol: )

I had thought new tubes were now available and in practice they would not be to hard to machine up out of suitable tube stock. So replacing the tube is a competitive option. It has its own risks around damage to the allow casting during the removal and refit process.

In the end you need to decide what works for you and make sure the selected option is executed correctly.

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PostPost by: CBUEB1771 » Wed Feb 03, 2016 1:51 pm

rgh0 wrote:I had thought new tubes were now available and in practice they would not be to hard to machine up out of suitable tube stock. So replacing the tube is a competitive option. It has its own risks around damage to the allow casting during the removal and refit process.


New tubes are available in both standard configuration with a fixed lower spring perch and also with adjustable lower perches. If I was going to cut the top of the tube off and weld on a replacement section I would start by removing the damaged tube from the hub carrier anyway. That would make it easy to turn a proper bevel for weld preparation using a lathe and to establish concentricity of the old tube and the repair section.
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PostPost by: Certified Lotus » Mon Feb 08, 2016 2:07 pm

I have a comprehensive overview of the steps needed to replace the strut shock tube on my rebuild thread lotus-elan-f19/elan-rebuild-story-t34178.html

I might suggest it takes a bit more effort that just heating it up.
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PostPost by: toomspj » Tue Feb 09, 2016 3:27 pm

Certainly, beating the tube with a hammer doesn't tend to go too well - i've tried that on ones I was planning to throw out! But with a bit of warmth and a press, I have always found it quite easy. (and quite easy is a relative term for doing anything on an Elan - even changing spark plugs can go horribly wrong).

I should have saidpotentially slightly bodgy for welding a threaded section on the top. I agree it can be a perfectly good solution, but I'd still probably take the tube out to do it so that i could pre and post machine it. I'm not saying it couldn't be done in situ but it just makes it harder to do a good job.

One warning if buying new tubes - there is a tendency for manufacturers to make the OD slightly bigger than the originals (from their perspective it is better than having an undersized one). That can make it difficult to reinstall and potentially lead to cracking of the bearing housing. So my advice is to carefully measure the od of the one removed and the replacement.

All the best and no offence intended.

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