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Discussion Starter #1 (Edited)
After some measuring I determined that the circle track suppliers sell the parts to make these lower links with off the shelf parts so no fabrication is required.

4x 1/2 inch hole high misalignment rod ends (5/8" thread) (2 RH thread, 2 LH thread)
8x 1/4" spacers
2x threaded aluminum rod - 16" length (ends are opposite threaded so you can adjust the length)
8x weather seals - unfortunately on the high misalignment ball joints the 1/2" weather seals dont work. I think I need 5/8.

Only ten minutes to install one side. Unfortunately I am having some new front brake hats machined so be a few weeks til I can test them out. I will report back on any noise.

If there is interest I will post part numbers, its important that the total width be 1.5" at the end.

Pros - eliminates bind and slop in suspension

Total Cost $120 shipped

Cons
  • they are actually a tiny bit heavier than the OEM, I was shocked how thin wall the suspension tubing is
  • might transmit a bit more noise
  • kinda bling
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Discussion Starter #2
Next up, I am going to do the same for the upper rear links - which are much more important. They move a lot in two axis so the rubber gets hammered (twisted and stretched), I am of the opinion that harder bushings are actually worse in the upper link because the movement of the arm will be restricted so the suspension cannot move as freely (its a minor thing but....). There is a guy on Ebay that sells the upper links, but I think I can do it for about half what he sells them for with out too much aggravation.
 

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Post part numbers please
(try saying that 3 times, fast)
I take it you didn’t struggle with the lower link stud?
 

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16" aluminum pipe? Steel spherical fitting threaded into aluminum pipe? Do they have any tensile ratings? Seems rather delicate for the task at hand?

I know I'm conservative about suspension strength - on my 87 wheel adapters, I went with steel rather than aluminum due to using lug bolts (not steel studs embedded in aluminum) for fear of stress failure. I thought removeable steel lug bolts into an aluminum hub was too weak.
 

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Discussion Starter #5 (Edited)
These tubes are designed for and used extensively as suspension links in Stock Car race cars. Probably not CUP but 3500 lb cars going 180 mph and banging into each other. The tubes are pretty thick wall (1/4"). I thought about the safety thing quite a bit, but when you hold them in your hands they are pretty beefy.

That said they also make similar tubes in steel and chromoly.

In fact the size of the rod ends are so large if I was doing it again I would just get 1/2" ID and 1/2" thread rod ends from the "economy" category and save some money.

The lower stud - shockingly came right out. My bushes were in pretty good shape, some one has been here before, I suspect when the PO had the current rear shocks installed they sold him bushings as well.
 

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Well done Erik. I'll be waiting to see how the upper rears turn out. Will they be the same materials and design?
And a long term drive report ;) Say a season or so.
Kind regards,
Redfox.
 

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Discussion Starter #7
Near as I can tell the upper links are identical to the lower only shorter. The implementation will be very similar, not sure if the yellow links are available in a 5" length so the arm may be a different color.

Adding one bit of info:

When I unbolted the in board end of the lower arm I attempted to move the arm through its range with just the outer end attached to its mounting, It required significant strength to push and pull the suspension arm up and down and the rubber squeaked and deformed. The new arm with bearings moves with zero effort as you would imagine. That effort to move the arm is additional wheel rate that the shocks have to try and deal with, it also slows the reaction....again probably nothing I will be able to feel but it helps me justify the effort and cost :)
 

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I take it as removing stiction helps the suspension to move freely, actually damping better, moving up and down freely, letting the valving in the dampers doing it's job. It's a guess, but having the prebind in the bushings as it was originally designed, is in my humble guess, an oldfashioned perspective and way to deal with suspension travel. I am probably wrong though. I would very much like to know the real reason behind this design philosophy, nut just that Lotus did this and that. I guess we must now realise, that suspension of high quality is now readily available for the aftermarket, as well as being factory installed on many sportscars.
An example. when I removed the otherwise new original Koni dampers on my Laverda and installed purposebuilt Öhlins, the motorcyle transformed from good to super good in driveability, comfort, grip and what not. The old (new) Koni dampers represented suspension developed decades earlier, although it was in the good end of the spectrum.
I think a similar approach could be done with a car like the Esprit. It was developed in the 1970'ies, and although Lotus did a good job with the car, many systems have moved on. Therefore we also now see Lotus taking another approach to building cars. More modern, more damped and controlled suspension with less stiction etc, are present or to be bought on order for the discerning prospective owner.
Another example. On my Corrado G60 I have original dampers and springs. Then on to a set of fresh ones. That worked well. But when I installed a purpose built set of KW adjustable coilovers, the handling and grip was transformed into a better car. Better materials, better more modern desing philosophy etc. all leads to this.
This is not meant as a critique of Lotus at all. On the contrary. But I also believe in moving on to new ways of doing things, at least to a degree. Lotus do themselves. Thay are of course not standing on the old spot not moving along development at all. On the contrary. They do try to do their best. As the did in the 1970'ies for example. Without, they wouldn't be Lotus.
So, if someone knows the real reason why Lotus chose to built in the pre-tension of the suspension bushings, link arm bushings and the track arm bushings, I'd certainly like to know. Is it really needed?
Was it because of tradition or was it because of that specific chassis design, or something else?
Should I take cover? ;)
Cheers,
Redfox
 

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Discussion Starter #9
I think that the rubber bushing design was used in every car, and still is for the most part. it is a compromise between performance, COST, acceptable ride quality in a street car, and maybe maintenance.

There are only a few road cars using spherical bearings, I think Mclaren uses some special weather protected bearings in some joints and I think the Porsche GT3 RS uses them also, IIRC I read that the Porsche then mounts the suspension sub frame with some very well thought out rubber isolating bushes to minimize NVH..

Fortunately the failure mode on these rose joints/rod ends when mounted in double shear is pretty safe. If the ball comes out of the joint, the joint still stays in place and rattles around mercilessly.
 

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If you install the suspension correctly, there shouldn't be any preload in the bushes. The suspension should be torqued at ride height with the car on the ground.
 

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That is exactly my point.
As soon as the suspension moves, the bushings, rubber or poly or something else, will bind. I did follow procedures myself to the letter, as I installed LOTAC polybushings.
But that is not the question. I tried to argue for why or why not to keep having that system, as it works with or against the dampers and springs. It would be interesting to know the real reason why they applied that system, and because of what? Would these bushings be in conjunction with or be counterproductive to todays far more responsive and advanced suspension?
Cheers,
Redfox
 

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Discussion Starter #12
Even if its torqued at ride height - when I look at the design of the bushings (any bushing) there is a metal sleeve glued into the rubber/plastic bushing. When you put the bolt through and tighten the body mounts onto the metal sleeve the whole thing is almost solid until the metal sleeve rotates on the bolt or the sleeve rotates in the rubber and deforms it. The sleeve is trying to slip on the bolt and the end of the sleeve is trying to rotate against the body mount.

So you torque it up, then after a few miles it loosens up, but its always changing, so tuning the shocks and springs is difficult. As things wear the amount of sticktion changes....etc. its minor but when you look at all of the joints on one corner of the car and add it up, maybe its something?

Its fun - it looks like an open wheel suspension now :)n I think my fancy aluminum arms were about the same cost as the LOTAC bushes for the arm? After I get some miles on it will better be able to judge if their is any value.

I really doubt I will notice any noise, any sound proofing this car had when new seems like it has completely degraded to nothing.

That would be another interesting project to do modern 3 or 4 layer sound proofing in the cabin like some of the guys have done on the high end vintage 911 builds. Might make long drives more relaxing.
 

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The metal sleeve is not supposed to rotate on the bolt - it is clamped to the frame. There is no sticktion - the motion is all in the rubber. And if the fasteners in your suspension is loosening up after a few miles, you aren't doing it right or there is something wrong with your suspension mounts.
 
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Discussion Starter #14
Hmmm

the steel sleeves in the bushings I removed do not appear to move in the rubber. Will look at it closer
 

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Hmmm

the steel sleeves in the bushings I removed do not appear to move in the rubber. Will look at it closer
They aren't supposed to move. All of the motion in the bushes is in the rubber itself. The rubber is bound to the inner sleeve, the inner sleeve is clamped to the suspension mount, and the outer part of the bushing is gripped by the suspension arm. Any motion is through deflection of the rubber.

This is why the suspension has to be at ride height when the suspension fasteners are torqued - otherwise there will be preload in the bushing.
 
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@Erik L

You should ALWAYS listen to folks who have mustaches! 😉 :LOL::LOL::LOL:
 

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Discussion Starter #17
Thanks Mike - I got it now. Makes sense. I can see how they actually can design and test a bushing to work with the amount of suspension movement planned for a car. I can also see how two identical size bushings could be different if one suspension arm moves through more degrees than another or a larger bushing with more rubber would be used in an arm that has to move through a longer arc. Interesting, I have always had the wrong idea about how bushings work. I can also see that if you torque them when the suspension is hanging it could immediately ruin a new bushing.
 

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Yes, we know that, but the question is why would such a system be used? And why use it today when there had been a developmentin suspension components such as for example dampers and springs?
For example: when exactly does the bushing begin to move? How does this affect the suspension travel and rebound?
Was it made for comfort or for shorter dampers and springs or as a sort of bumpstops or something else?
Cheers,
Redfox
 

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Yes, we know that, but the question is why would such a system be used? And why use it today when there had been a developmentin suspension components such as for example dampers and springs?
For example: when exactly does the bushing begin to move? How does this affect the suspension travel and rebound?
Was it made for comfort or for shorter dampers and springs or as a sort of bumpstops or something else?
Cheers,
Redfox
The answer is probably yes to all of the above, except for bumpstops. I would throw in cost as a factor as well.

Again - the bushing does not move. The rubber in the bushing deforms as the suspension arm moves about. There is very little friction in the bushing - only spring rate. The suspension design takes the durometer of the bushing into account when considering spring rates, bump, rebound of the suspension system - just like the tire sidewall is considered. When you think about it, the rubber in the bushing actually assists the damper to return the suspension to rest position as the deformed rubber is storing energy that gets released when the force on the wheel changes.

Developments in dampers and springs hasn't really changed the basic requirements of a system to mount wheels to a chassis. Regardless of the type of spring (rising rate, torsion, air, leaf, transverse, pick your poison) or what it is made of, it still does springy things. Dampers are there to stop the springs from doing springy things when you don't want them to. At their fundamental level, dampers introduce friction to control how the system responds to impulses. The developments in dampers has been to better manage the application of the friction to the system and to deal with the heat that friction generates.

Noise, vibration and harshness from the suspension are reduced with rubber bushings. Most people would not tolerate a hard suspension that spherical bearings introduce. Neither would you I'm willing to bet if you have to drive the car 4 or 5 hours at a stretch over less than racetrack roads. The suspension will be more sensitive to input since it doesn't have to take up the compliance in the bushing before the car starts to turn for example. That can be a good thing if the rest of the suspension is tuned to cope with that kind of rate of change. A compliant suspension means loads are distributed gradually throughout the system, including the contact patch. This means you need to consider the tire as well - the tread and sidewall may not be able to cope with the change in the way that cornering loads are applied. There is also more impulse loading on the suspension mounts on a smaller surface area, so I would recommend keeping a close eye on the fasteners and mounts as the ones in the car are not specified for that kind of loading.

I think if you were to look at pretty much any car or truck these days, even some absurd supercar, they are all using this type of suspension. Sure, materials have changed, but the concepts are identical. Active suspension is the only currently viable way of getting around it.

The more I think about this, the more I come up with to think about. Suspension is about keeping the contact patch on the road by managing the energy imparted to the system by acceleration, braking, cornering and road imperfections. That energy has to go somewhere. Building compliance into a system is a way of managing the way that energy is dissipated. Good suspension design takes into consideration a LOT of things, including the rigidity of the chassis it is attached to. Moving where energy is stored and released may have unintended consequences.

One thought that crossed my mind is that without the bushings to absorb some energy and reduce the impulse transmitted to the frame, where does that energy go? In a rear suspension, it goes to the suspension mounts, which are rigidly attached to the frame. The frame now has to dissipate this "extra" energy and deal with the intensity of the application of the energy. The body provides a considerable amount of rigidity in an Esprit. That energy will get transmitted to the body mounts, which are metal bobbins glued to fiberglass. I would not be surprised to see some cracks start to emerge in the fiberglass over time.
 

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Discussion Starter #20
Mike you are really depressing me :(

"Moving where energy is stored and released may have unintended consequences."

This really has my wheels turning. I can only hope many of the suspension mounts are over built a bit.

One thought along these lines:

If a tire hits a bump and the suspension deflects upwards. The rubber bush would twist as you describe and add some rate to the suspension. It would also add some force/torque to the mount.

With a bearing, there would be no torque on the mount. Just a bit more upward force transmitted to the mount that is not absorbed as the rubber bush also compresses.

Maybe it all balances out 🙏 (praying)

Interesting to think about.
Discussion has also opened my eyes to Delrin bushings in applications where there is only one axis of movement.

The Delrin would rotate around the metal sleeve and have almost zero deflection, self lubricate (I think) and be low cost to fabricate. The down sides are similar to bearings as described by Mike G.
 
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