Lotus Elan

Front Shock absorbers

PostPost by: Elseezed » Sat Nov 10, 2018 10:58 pm

AVO's fitted as in photo. Platform wound to top and still could not get up to the ride height. Springs supplied were 1.9" x 9" x 150, changed to 1.9" x 10" x 175lbs. This set up is still compressing the spring to much to achieve the ride height, thinking of raising lbs to 225lbs. Any info on spring rates would be useful.
imag0687.jpg and
AVO soft spring.
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PostPost by: alanr » Sun Nov 11, 2018 8:58 am

I am very much a newbie here and personally still finding my way around my +2 but it looks to me from your photo that spring length is the problem and not spring rate.
Alan
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PostPost by: alanr » Sun Nov 11, 2018 4:03 pm

Elseezed.

The info I have found,how correct I do not know, is that the the original Armstrong front springs on a +2 were 14.19inches free length and 110lb/in. How applicable tthis is to your set up I guess is questionable but certainly should put you somewhere in the ball park.
The springs that SJ Sportscars currently sell at the moment I have discovered for the later +2's are 14.59 inches long having had a discussion with them in the last few days over my search for shocks and springs. The early +2's I have no knowledge of length.
Alan
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PostPost by: Elseezed » Sun Nov 11, 2018 5:17 pm

imag0754.jpg and
AVO shock

imag0472.jpg and
Fitted 10" 175lb

Alan, I will contact Faulkner Springs regarding a solution. A coil should support the car but not to be coil bound as in my case.
As previously mentioned fitting longer springs requires compression so I would like to avoid that. Could fit an 11" spring with a struggle.
Had a Ginetta G15, same problem with 100lb spring, ended up with 150lb springs fitted and that had very little weight in the front ( engine at rear).
Les
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PostPost by: Elseezed » Mon Nov 12, 2018 2:35 pm

Doing a comparison with a Triumph GT6.
GT6 weight is 864kg standard front springs 220lg or fast road 330lb.
+2 Weight is 882kg. So logically a front spring for a +2 should be 250lb.
Spoke to Faulkner's, they supply springs but not specifically to any model.
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PostPost by: baileyman » Mon Nov 12, 2018 3:06 pm

GT6 and Plus 2 have the same geometry?

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PostPost by: 69S4 » Mon Nov 12, 2018 4:32 pm

Elseezed wrote:Doing a comparison with a Triumph GT6.
GT6 weight is 864kg standard front springs 220lg or fast road 330lb.
+2 Weight is 882kg. So logically a front spring for a +2 should be 250lb.
Spoke to Faulkner's, they supply springs but not specifically to any model.
Les.



Isn't a 250lb spring over double the std rate? That's going to be one very hard ride on the road. I'm not sure what the F/R weight distribution is for a +2 but if it's roughly 50:50 then the front springs will be supporting 440kg of that total or (again roughly) 450lbs (changing units) per wheel. If you have a couple of inches of preload and another couple of static sag that would need a spring rate of around 110 lb/in (roughly std). There are some geometric considerations because of the shock angle but that's beyond what I can do at the keyboard.

I'd have thought a 110lb spring long enough to give you that 2" of preload in the middle of the shock adjusting range and that doesn't end up coilbound on full shock travel would be your starting point. 250lb sounds like a filling remover.

Or, given that my suspension knowledge is pretty rudimentary and based on respringing a few motorcycles, maybe I've got the approach completely wrong, but a calculation that gives twice the std rate would ring warning bells with me.
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PostPost by: alanr » Mon Nov 12, 2018 5:55 pm

Stu,
Earlier you said you bought Spax shocks, I am slowly coming around to similar thinking for similar reasoning! However, re-Springs, I am slightly concerned by your comment about the supplied springs when fitted being at the bottom of the platforms at normal ride height. Were these 14inch/110lbs?.. PMS I see do a 12inch at 140lbs but I think that 13inch would be a better compromise at 125lbs which I have found that I can obtain elswhere. Any thoughts?

Thanks,

Alan
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PostPost by: Elseezed » Mon Nov 12, 2018 8:07 pm

Spoke to Avo today. I get it now, Lotus method is 14" x 110lb spring compressed into the coilover, so why did my Lotus supplier send me 9" x 150lb springs with my AVO's?
Normally on a coilover set up shorter springs are used as Triumph.
At the moment my setup works fine, it just looks wrong.
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PostPost by: Chrispy » Mon Nov 12, 2018 10:49 pm

I used the Protech's on the front of my +2. No complaints other than the springs rub on the upper end of the adjustment threads on the shock body. Never going to need that adjustment, just looks unsightly. I pulled Spax's off and wasn't impressed with the design.

I used GAZ's on the rear which I am quite happy with.
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PostPost by: 69S4 » Tue Nov 13, 2018 9:37 am

alanr wrote:Stu,
Earlier you said you bought Spax shocks, I am slowly coming around to similar thinking for similar reasoning! However, re-Springs, I am slightly concerned by your comment about the supplied springs when fitted being at the bottom of the platforms at normal ride height. Were these 14inch/110lbs?.. PMS I see do a 12inch at 140lbs but I think that 13inch would be a better compromise at 125lbs which I have found that I can obtain elswhere. Any thoughts?

Thanks,

Alan


My car's a two seater so the std front spring rate is 75lb/in but the principle is the same. The PMS springs were 14" (from memory) and they were compressed down to 9" on the Spax units before fitting. That's 5" or 375lbs of preload per wheel. The workshop manual, incidentally, says the std springs are 16" and compressed down to 9 1/4" at 75lb / in, so somewhat more preload than I have (514lb). The preload bit is important if the suspension is going to move under road load. You also need some sag in the system to allow the wheel to move down when weight is transferred off (e.g. over a rise or round a corner).

Using really heavy springs with no preload and little sag is going to need a huge 'impact' to get minimal suspension movement. What movement there is is then going to need some serious damping to control it. How the damping characteristics of the various shock absorbers on the market vary( if they do) and what's the most suitable for the Elan's road needs is something I pondered before buying but couldn't find any info at all on.

It did surprise me that the fitted springs only gave the correct ride height at the bottom of the adjuster ring. I'm reserving judgement on their suitability until I revisit the front suspension over the winter and see if there's any settling. If there is that should put the adjuster back into a more acceptable part of the range.
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PostPost by: alanr » Tue Nov 13, 2018 5:10 pm

Chrispy wrote:I used the Protech's on the front of my +2. No complaints other than the springs rub on the upper end of the adjustment threads on the shock body. Never going to need that adjustment, just looks unsightly. I pulled Spax's off and wasn't impressed with the design.

I used GAZ's on the rear which I am quite happy with.


Thanks for the input. :D
Various people have suggested Protech and I am told, but not physically seen any yet, that they really do look the business. However, I just wonder what the alloy body will look like after a couple of years use. Also I note your comment about the spring rubbing.
Alan
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PostPost by: Elseezed » Tue Nov 13, 2018 5:59 pm

Update: I have ordered the correct springs from SJ Sportcars, should arrive tomorrow. If I remove the AVO coilovers, take them with the springs, Chris Foulds will assemble the units. Just need to then refit to car.
Thanks Alan for raising the post and Stuart's input.
Les
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PostPost by: JohnCh » Tue Nov 13, 2018 6:08 pm

alanr wrote:Various people have suggested Protech and I am told, but not physically seen any yet, that they really do look the business. However, I just wonder what the alloy body will look like after a couple of years use.


I've been running Protechs on my Westfield for over 10 years and they still look great. To be fair, the car is rarely driven in the wet and is stored in a heated garage with humidity levels kept at 50% or lower, but part of the credit is likely due to the clear anodization option Protech offers. The front shocks are fully exposed so take a bigger beating from rocks than they would with enclosed bodywork, yet no problems.

-John
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PostPost by: Mick6186 » Tue Nov 13, 2018 6:22 pm

I have the adjustable front shocks (new) on my +2 130/5 with standard springs. To achieve an acceptable front ride height I have had to have the ride height adjuster at the lowest setting, and even then the bottom wishbones are nowhere near parallel with the ground. All of the top mounts and bushes are as in the manual. Everything moves freely when I bounce on the wing. Something doesn't seem right. The car hasn't been used on the road for at least 15years but is nearing completion,
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