Adjustable Spring Platforms – Elan Rear Suspension.

The purist might adhere to the doctrine of ACBC – “Make It Adjustable and They’ll Get It Wrong”.

I will agree to disagree, there is a very good reason to afford the luxury of being able to make adjustments to the front and rear suspension of the elan.

The luxury of adjustment provides the ability to “dial in” that optimum performance suspension setting, be it for an improved suspension or ride height setting, you would be astounded at the difference a fully optimised and aligned suspension will make to the handling and drive experience of the lotus elan.

Don’t take it for granted that your elan suspension is correct, while the handling was pretty good straight out of the box, the elan can be vastly improved in that respect.

The fitment of uprated rear coil springs mounted on adjustable spring platforms (perches) is the first step to begin fine tuning the rear suspension of the elan. But for the naysayers out there, if you are happy with your elan as it is, stop reading now.

At first glance, the large amount of work involved may appear to be overly complicated and expensive for most, but that wont be the case if you are capable of carrying out all of the the required work in your own workshop.

This job can be presented as a totally professional installation, and at a fraction of the cost than what you might imagine.

The following story may help you to understand just what is involved and help you decide whether it is for you or not, but be warned, your results may be completely different to that of the writer of this article, no guarantee of any kind is implied or expressed.

You may wonder why we keep on about being able to do many small engineering and fabricating projects yourself. There are several reasons, cost and personal satisfaction being two that quickly come to mind, ah, but you say, there are many elan owners out there who wont have the skills, nor the tool or workshop resources, to be true.

If, over time, you could lift your mechanical and engineering skills from basic to advanced, imagine how much your skills will repay you over the ensuing years of classic car ownership, the more mechanical/engineering skills that one has, the less it will cost to maintain any given pride and joy. And without being smug, the writer is amazed at how many people buy a lotus elan, but have little in the way of mechanical skills and resources to maintain these classic cars. If you have very deep pockets, then that’s OK, it’s not going to be a problem, but you don’t have to dig deep when you have some well honed DIY skills and some workshop gear.

DIY engineering, it provides the ability of to begin with $50.00 worth of material, then after applying your DIY engineering knowledge and skills, making the resulting project the equivalent to a workshop bill of say, $600.00 to $800.00, or perhaps more, if the project had been carried out at outside workshop, believe it or not, its fact. But it goes without saying, if you don’t understand what you are doing, then leave well enough alone.

Owning a classic elan is no different than owning any other classic sports car, it is generally based on passion, and the desire to own a nice example of a particular make to drive around and enjoy, but if that desire also means you’ll be making constant trips to the mechanic, or elan specialist to maintain your pride and joy, the classic car ownership deal may be very short lived if the maintenance costs and repair bills prove to be too much.

Workshop charge rates may range from $80 to $140 per hour…  and as you would, or should understand, with a lotus, not much work can be completed within the hour.

If you don’t enjoy getting grease on your hands, and you don’t have an issue with the maintenance costs of your pride and joy, then the best of luck to you, but many DIY enthusiasts would agree that you are missing out on an essential part of classic sports car ownership…

But enough of the preaching.

Let’s discuss the installation of an adjustable rear spring platform conversion on the lotus elan S1 to S4.

For this job, the elan will be off the road for several days, so don’t plan on attempting to complete this project over a single weekend, the job entails a lot of work, and if you are into the Pro DIY category, you will need access to following gear.

• Lathe and associated tooling.
• Welding gear, Oxy/Acet, MIG or TIG will be OK,
• Plus the usual collection of normal workshop tools such as spanners, hammers, sockets, etc etc.

The photo above illustrates the number of parts (After dismantling) that make up both the rear struts. A nice collection of lotus parts. Now the work can begin in earnest.

The first step is to source, or DIY manufacture the threaded strut barrels, and the aluminium threaded adjustable spring platforms. The threaded barrels are machined from EN25 hollow bar or equivalent. We wont elaborate on the machining details as that could take up a whole page, we are assuming that your machining skills are a given. So first thing is; decide what diameter coil springs you require.

Many people choose 2.25″ ID springs (57.15mm) because they are easy to source, but if the 2.25″ ID size is chosen, the strut shaft and seal will be left exposed to road grim and grit. A better option is to chose the larger coil ID of 70 mm which will allow the installation of a protective rubber gaiter (Generic motorcycle donor part) that will protect the hard chrome plating as well as the strut rod seal, we will show photographs of that setup further on.

The most important benefit of the wider Dia coil springs is that the essential and original type of Aeon bump stop can be installed with the larger ID springs… and please, DO NOT omit the correct Aeon bump stops, they are an essential part of the elan rear suspension, and help enormously in providing correct handling characteristics, and ride, anything less, wont work anywhere near as well.

There are several components that go to make up the threaded adjustable platforms, basically we have two of everything, because there are two struts to fit out, so once you are armed with the required items, you can then get to work. But first, the original elan  pressed metal spring platforms need to be removed. The chassis should be jacked up and placed on ramps or floor stands, or placed on a garage hoist to lift the car off the ground so that dismantling work can proceed.

Once the struts are completely removed, they can be dealt with on an individual basis, a spring compressor tool is required to compress the coil springs so that the strut rod nut can be removed, the spring assembly can then be removed from the strut. The strut tube retaining gland nut can be undone and the strut insert removed, there will be a quantity of oil inside the strut tube housing, which is there for cooling purposes & nothing else. There is probably no need to remove the wheel hub and or axle, but if these items require checking, then while the struts are out would be a good time to carry out service or repair work.

The threaded barrel, platform and lock ring all mounted on the strut tube, all that is required to secure the barrel on the tube is three small spot welds top and bottom, applied at 120Deg spacing.

Do not allow the spot weld bead to build too high otherwise the threaded alloy rings wont screw onto the barrel, a hand file can be used to reduce any weld bead high spots to required correct clearance for the threaded collars.

The threaded barrel should be zinc plated to protect against rust. The alloy rings are either machined from high quality solid round aluminium, or they can be sand cast aluminium then machined and finished on the lathe to fit the barrels.

A garage press can be used to remove a threaded barrel, as well as install a new threaded barrel. DON’T ever use a hammer to impact the barrels down the tube, because damage could result to the various parts of the strut and or platform. The press illustrated above is only 12 ton and is more than adequate for the job. Do NOT attempt to hammer the collar down the tube, it will become damaged.

The easiest method to remove the original lotus spring perches is to cut in from each side (At 90Deg) towards the strut tube (Do Not slice through the strut tube wall) with a thin abrasive cut off wheel mounted in a 4″ angle grinder, make sure to wear proper eye safety glasses when carrying out this operation. once the platform has been cut from both sides, apply plenty of heat (Oxy torch) to the bottom flange of the old platform, as the bronze/braze material will need to be softened before the platform or perch can be removed with a light tap with a hammer.

Afterwards, clean all paint and remove any high spots and rough areas with a flap wheel (Angle grinder) or with a hand file. The strut tube has to be clean and free of paint, burrs, and high spots before the new threaded barrel is pushed/pressed down the strut tube. DO NOT PRESS an overly tight threaded sleeve onto the strut, if the sleeve cant be pushed partly onto the strut tube by hand force, there’s a chance that it will be to tight, clean the outer surface of the tube with a file and start again.

The spring caps and rubber gaiters, the inner metal tube, the top of the gaiter is mounted to the tube and held with a zip tie, that is all that is required. The steel tubes are pressed into the underside of the cast spring cap, this work is completed in the lathe.

Photograph above illustrates the position of the threaded barrel on the strut tube. and shows how the rubber gaiter encloses and protects the hard chromed strut tube, the spring cap holds the gaiter at the top, next you will see how the entire strut looks fully assembled.

Now we can see how the completed spring platform conversion looks. The alloy collars are at the lowest setting for ease of fitting the  coil spring, final spring height adjustments are made with the car fully assembled. “C” spanners are employed which locate in the milled slots of the rings to adjust up or down the threaded barrel, adjustment is easy to do. Note also the large wheel axle nut has not been torqued up, that is one of the last jobs to do after the struts have been re-installed back onto the car.

The simple, elegant, well designed rear suspension of the lotus elan. Note the LH – RH threaded adjuster in the rearmost straight tube of the A arm, (One each side) this simple adjuster allows correct toe settings to be dialled into the rear suspension, and it takes less than three quarters of a turn (either way) to achieve the correct toe setting on each side of the chassis. (Even the best fabricated A frame wont be correct)
(The CVDS conversion is yet to be fitted above to complete the picture.)

What we have just outlined has been completed in house at Croucher Engineering – elantrikbits. The system does work, and has contributed to a very precise and better handling lotus elan… But you are free to make up your own mind about the conversion. The wheels are 14″ x 6″ Aussie Simmons fitted with 60 series lower profile tires. The larger wheels provide a generous amount of room for the lower outer A frame bolts, and the narrow springs provide plenty of clearance between the tire and the adjuster collars.
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The Following Data Could Be Useful For The Chosen Spring Manufacturer – For Rear Coil Springs For Lotus Elan.

Spring OD:          90mm. (3.54”)
Spring ID:           70mm. (2.75”)
Wire Dia:             10mm. (0.393”)
Free Length:        380mm. (14.96”)
Fitted Length:     292mm. (11.496”)
Spring Rate:        78-80Lbs.
Working Coils:     13.

So there you have it, a detailed overview of the rear suspension upgrade incorporating an adjustable spring platform kit, yes, it is a large amount of work, and the cost will vary depending on the amount of machining and fabrication work you are capable of doing your self.

Two or three years after this upgrade was completed, we designed/built and installed an adjustable blade type rear anti roll bar (ARB) to the elan, you can learn more about that project here.
May be you also want to learn about how to CAST METAL in your own home workshop.