Lotus Elan

Spax dampers

PostPost by: Roy Gillett » Tue Jun 23, 2009 5:01 pm

For the second time in four years I have had the top snap off a Spax front damper releasing the spring with potentially disasterous consequences. Last time it punched the top yolk of the damper up through the fibreglass having escaped from the turret. This time the picture will show that the spring had gone 'C' shaped and was potentially about to ping out and damage something / somebody. Believe me I was VERY careful dismantling this lot. Spyder Engineering from whom I bought the dampers say they have got fed up with Spax and will not deal with them any more. They believe the top of the damper rod is too brittle and just shears off, but Spax will not accept this (nor will they accept waranty claims.).

I will certainly never buy their dampers again. One failure is unfortunate, two is just totally unacceptable. The first one failed after 6000 miles, this one after 10,000.

Caveat emptor!

Roy
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spring!.jpg and
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PostPost by: johnsimister » Tue Jun 23, 2009 5:43 pm

I share your view of Spax, the recent products anyway. I started a topic about the rock-hard damping in the rear Spax I bought from Paul Matty, but there were other snags as well. These were:

1) The piston rod is too thin, so Spax makes it thick enough to support the upper spring platform and contain bump damping forces by adding a circlip on which the platform sits - hardly robust.

2) There's too much travel on extension, leading to more droop than the suspension ever needs or the driveshafts can cope with.

3) In my car's rear strut tubes, admittedly of the adjustable platform variety which could conceivably have made a difference, the Spax inserts were too short because the retaining nut bottomed out before reaching the top of the damper. I had to make up a spacer to fill the gap.

Contrast that with the Konis I fitted instead (from Tony Thompson). Proper piston rods with a machined step for the platform. The right amount of travel. The right length of damper body to fit the strut tubes properly. And the right damping forces.

I eventually got a credit note from PMSC, but PM was adamant that all the above, including the ludicrously firm damping even on the softest setting, was 'just your opinion'. We agreed to differ. Spax of course said there was nothing wrong with the dampers at all when they were sent there for testing.

The odd thing is that Spax used to be quite good. My Elan has old Spax on the front, non-gas and fitted in the late 1980s, and they are still fine. I'm now waiting for their top mounts to break...

John
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PostPost by: enskr » Tue Jun 23, 2009 6:38 pm

I have to agree also - I've recently fitted rear spax and I'm pretty unimpressed. The circlip on the piston rod that John refers to is especially cr*p in my opinion - in bump the whole axial load is borne by the circlip bearing onto the spring abutment plate - I'm just waiting for it to fail and daren't adjust the dampers off minimum for fear of the damper rods being rammed straight through the plates and through the Lotocones.
From the other comments here it doesn't sound like adjusting them would improve anything anyway!

From memory I tried to get some Konis in the first place - should have tried a bit harder, but at the time I just wanted my car back!


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PostPost by: terryp » Tue Jun 23, 2009 6:43 pm

Roy
Sorry to hear about your shock absorbers
In the event of my shocks being replaced I will not be buying Spax now.
Hope you and Sandy are well

All the best

Terry
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PostPost by: JJDraper » Tue Jun 23, 2009 9:51 pm

I went through a spell of snapping Spax dampers on my +2: three on the front, also at around 8-9,000 miles each (after the third, I went to the factory in Bicester to voice my concern). They were supplied by PM and used Spyder springs. This was over a period of eighteen months, ending about five years ago. Spax suggested that the springs were getting coil bound and that this transmitted shock loads directly to the top mounting, leading to fatigue failure at suspiciously similar mileages. They took my car in for testing to check the suspension travel and alignment to see if there were any other external influences - they found none. The upshot is that they made a pair of dampers specifically for my car and said that they had altered the design of the machining of the top shoulder on the piston rod to 'beef it up', and that this modification would be incorporated into their designs. They also fitted their own springs with less coils.. The dampers are still on the car after about 35k miles and still seem fit. Spax were very helpful, but this is a case of sloping shoulders for the true cause of the problem. If you contact Spax, give them the serial number on the unit and get them to check the date of manufacture, as stock can sit on a shelf for a long time.

Everyone I spoke to; Spyder, PM, Spax - even this forum at the time, said 'we have never heard of this happening'. So if they are all still saying this, it is not true!

I also fitted one of Spyder's rear twin wishbone set ups a few years ago - guess what, the damper snapped after about 10k miles... Spax damper...

I put it down to rough roads around the area... maybe not?!

On a completely different and more positive note, I started out on motorbikes - variable rate springs were (still are?) the thing - comfortable when cruising but harder when pressed. Doesn't this apply to cars as well? Especially light cars like ours. Where are the variable rate springs for Elans?

Jeremy
Attachments
+2 RH Suspension failure.jpg and
Oddly enough the car was still comfortably driveable... I only found out when it made clanging noises going over some potholes..
+2 LH Suspension Failure.jpg and
Dismantling was rather dangerous
+2 LH Suspension Failure 2.jpg and
+2 rear suspension failure.jpg and
This caused the only time the car was not able to drive home in nearly ten years...
Top mount failure.jpg and
Classic fatigue failure...
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PostPost by: jimj » Tue Jun 23, 2009 10:10 pm

I know the Great Jim Jackson uses TTR inserts without any problems.
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PostPost by: ncm » Wed Jun 24, 2009 1:49 pm

Gents, have either of you,or have you allowed anybody to,attempted to undo or tighten the knock-on nuts with the wheels in the air? Many years ago I was foolish enough to allow a tyre fitter to jack up my car and then loosen(&tighten)the 3-eared nuts. The next time that I lifted the car to work on it there was a loud crack from the front after it had been in the air for half an hour....investigation revealed a spring bent out like the above pictures. In my case an internal screw at the base of the rod had sheared and the rod itself had been bent by the force of the spring trying to escape :shock:

Brian.
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PostPost by: JJDraper » Wed Jun 24, 2009 5:26 pm

No...

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PostPost by: denicholls2 » Thu Jun 25, 2009 3:54 pm

The excellent pictures suggest the failure is at the stress riser at the bottom of the threads. This will always be the weakest part of the shaft, but suggests a problem in either materials or diameter, or in the way the threads are cut into the rod.

I suspect most of us would much prefer a milder steel shaft that bent instead of breaking under high stress. We might need to check that things were straight more frequently, but would probably drive home after any incident, and disassembly would certainly be less risky. But milder steel may be more rust-prone.

I may be thick-headed, but the explanation of coil binding makes no sense to me. When the spring is coil-bound, it becomes more like a rigid cylinder and my intuition says it will carry less stress to the shock rod, not more, because the shock is disengaged vertically and sees only horizontal load, and that reduced by the friction of the bound coils. I would think that much more stress on the rod would come from the shock bottoming before the spring became coil-bound. This would transfer all of the additional vertical load to the shock instead of letting the spring carry it. And ride-height adjustments that favor the possibility of this condition could be an explanation of rarity in general, but frequency for the those with problems.

Given that the stresses of carrying a Lotus body are lighter in general than typical automobiles, I'd opine that a bit more engineering is in order at Spax (if as mentioned it hasn't happened already.) And given the inherent safety concerns, keeping mum about a common problem is hard to accept. This side of the pond, the litigation cost and ill-will demonstrated here would be far worse than eating crow and upgrading existing owners.

I shall now pay closer attention to my own Spax. Parts that expensive should be designed with real-world stress estimates in the foreground. Thanks for the post!
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PostPost by: Roy Gillett » Thu Jun 25, 2009 4:38 pm

ncm wrote:Gents, have either of you,or have you allowed anybody to,attempted to undo or tighten the knock-on nuts with the wheels in the air? Many years ago I was foolish enough to allow a tyre fitter to jack up my car and then loosen(&tighten)the 3-eared nuts. The next time that I lifted the car to work on it there was a loud crack from the front after it had been in the air for half an hour....investigation revealed a spring bent out like the above pictures. In my case an internal screw at the base of the rod had sheared and the rod itself had been bent by the force of the spring trying to escape :shock:

Brian.



Certainly I always 'start' loosening my knock-on with the wheel on the ground in order to stop rotation, but why should hitting the spinner hard snap the damper rod? Andy at Spyder says he has 'tested' Spax damper rods in the past by hitting them with a 2 pound hammer when held in a vice and they just snap as mine and Jeremy's have in use. He too thinks they should bend rather than fracture given this treatment.

I agree with denicholls2 with such a safety-critical item if there is a known fault Spax should be pro-active about solving it and warning existing customers, not washing their hands of it and disowning the fault.

Roy
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PostPost by: JJDraper » Thu Jun 25, 2009 8:53 pm

denicholls2 wrote: We might need to check that things were straight more frequently, but would probably drive home after any incident, and disassembly would certainly be less risky.


Not sure what you are getting at here... I am a bit of a 'Malcolm' - (ref Ogri in older Bike mags). I spend a lot of time worrying about vague noises, knocks, wobbles etc and in my M/Cycle days would dismantle an engine to find out why it was so quiet. There was no warning or prior incident to the failures...

No response to variable rate springing yet...

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PostPost by: rdssdi » Thu Jun 25, 2009 10:13 pm

This is a most interesting subject.

I have Spyder supplied chassis, suspension arms, springs and Spax shocks on my +2. I have done very little driving and to date have not had a problem. It does appear to be a problem as these multiple failures demonstrate.

Are all these shock failures occurring when using Spyder springs as well as Spax shocks? Other after market springs?

I am now waiting for a set of 6 Spax shocks for a TVR Vixen. I have been waiting since March. The company and their U.S. importer have not been very helpful. This thread has certainly made me think.

Is Koni presently offering shocks for the Elan +2? Are replacement springs for the 2 available that emulate the original in number coils, ID, rate and free length?

Bob
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Front shock spring
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PostPost by: paddy » Thu Jun 25, 2009 10:21 pm

I recently replaced Spax all round with Koni on the rear and TTR on the front. It sounds like it's a combination that several here have used. In relation to springs I assume you're asking about the fronts; the answer is yes, you can get a range of springs from a spec similar to original to stiffer fast road and race. The only difference you need relative to original springs is a shorter free length to take into account the different platform height when the dampers have adjustable platforms.

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PostPost by: GrUmPyBoDgEr » Fri Jun 26, 2009 10:09 am

Those pictures are frightening to say the least & the suppliers explanations disgusting.
Testing the damper rod breaking point with a 2Lb Hammer incredible, that man deserves a job in Aerospace :roll:
When I started the rebuild of my S4 I got a very good deal from Spyder for their chassis, wishbones, RSC, dampers, springs & a host of other bits so fair do's.
However, after fitting the RSC to the chassis I decided that the geometry just "didn't look right", without doing any measurements etc. it came off before the chassis hit the ground.
Assembling the supplied front springs to the supplied adjustable platform dampers was very, very scary.
The free length was incredible & when fitted the coils were very close together & buckled all over the place.
TTR modified my rear struts for 2.5" springs, put his dampers in & supplied matching front & rear springs.
Fitting those front springs went the way I would normally expect with no fear of serious injury, as previously encountered
But to get to the point, in this Country where I live, changes from anything standard on cars is very strictly controlled, in the name of safety.
e.g. A non-standard Steering wheel or Road wheels have to be supplied with correct paperwork & that is then entered into the registration document.
Even a change of tyre size must be approved by the T?V.
In comparison there is practically no control in GB.
The MOT doesn't check part numbers & suppliers of parts do not have to subject their components for official testing.
Owners can do practically anything they wish to do to their cars provided the inform their insurance company about any
"changes to performance"
Now that IMHO in these days of overpowering "GB elf & safety" is close to being miraculous.
Nevertheless that situation gives us all (in GB) freedom to do things to our cars which in other countries would be impossible but on the other hand we leave ourselves wide open when unwittingly using components such as the dampers being discussed.
Basically that supplier needs to be punished for supplying those parts but where & how far can you go without arousing the interest of the national & European legislators (read "Bean counters")
It's great to still have "freedom of choice" & that this forum puts up warnings like the ones in this thread.
Oh well Friday rant over :oops:
Hope my rambling makes some sort of sense :roll:
Have a good weekend.
John
Last edited by GrUmPyBoDgEr on Sat Jun 27, 2009 11:44 am, edited 1 time in total.
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Editor: On Sunday morning, February 8th 2015, Derek "John" Pelly AKA GrumpyBodger passed away genuinely peacefully at Weston Hospicecare, Weston Super Mare. He will be missed.
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PostPost by: rdssdi » Fri Jun 26, 2009 11:35 am

I received my front Spax dampers from Spyder with the coil spring attached. They performed this service gratis as I had purchased both dampers and springs from them.

Bob
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