My weird uneven spring height issue - guess the cause?

[Sp!ke]

If one of the spring appears as bent, with the weight of the wheels, what is the lenght of the shock , surely that must determine the travel, the spring can move.

Both shocks are new and length is the same as the old shocks.

There are other things that determine this, spring pressure and ARB for instance.

 

[Roger Jones]

"I'm wondering about the the rubber bushes at the top of the damper mount but I cant see how these would effect the ride height unless the bush had collapsed completely."

For all I know, the front may be different, but it was the replacement of one of the rear rubber bushes with a deeper one that cured my SL500 of its lopsidedness -- and brought it within WiM tolerances -- which had been caused by a previous owner replacing one old spring but not the other. This was fixed in an hour by SS Motors in Weybridge, who showed me several bushes with their different thicknesses, and said that it was a favoured solution to a common problem (often caused by those who refuse to replace springs in pairs).

 

[Rory]

Forgetting the wishbones have you tried taking accurate measurements of the spring perch position relative to the rest of the body? Even try leveling the car to the ground using the Xmember as a reference then measure up to the perch from the ground.

Appreciate that sp!ke has already thanked this post, but surely leveling the car with a jack and then seeing where the differences are has to be the way forwards, although it might be a bit tricky to see what's going on without a lift?

 

[Sp!ke]

For all I know, the front may be different, but it was the replacement of one of the rear rubber bushes with a deeper one that cured my SL500 of its lopsidedness -- and brought it within WiM tolerances -- which had been caused by a previous owner replacing one old spring but not the other. This was fixed in an hour by SS Motors in Weybridge, who showed me several bushes with their different thicknesses, and said that it was a favoured solution to a common problem (often caused by those who refuse to replace springs in pairs).

I think you are referring to ther spring pads which I agree could be used as a quick and dirty way to even up the car a bit. I think it is a bit of a bodge though .. as the underlying cause is still present.

That said, I'm currently on #2 pads on the fronts so could only make an 8mm saving by going to a #1 pad on the rhs. I suppose its worth a try but I'm getting really tired of taking these springs out without the proper compressor. It's pretty dangerous work if I am honest.

 

[corned]

It's pretty dangerous work if you are dishonest too!

 

[Sp!ke]

I've just booked in the car at Wheels in Motion on thursday.

They seemed pretty coonfident in finding the cause, so fingers crossed its something simple like camber adjustment.

 

[Sp!ke]

So I took the car to Wheels in Motion today and had the car all hooked up onto their very fancy machine.

What a professional outfit they are. I was made to feel very welcome and allowed into the work area and discuss what the problem was and how and why they were able to rule out certain things.

So the good news is that the chassis is straight and not twisted or something as I feared. Whilst there was some relatively minor alignment issues going on, it was thought that these could not be the cause of my spring height issue. So I'm happy to have ruled these out and the exercise was well worth doing. Overall, a good experience and I'll be returning to get the car properly setup once I nail this particular issue.

However I still have the height issue unanswered and right now its still pointing at the springs. I guess it is possible for the old set to be knackered and the new set of springs to be faulty but the odds must be very slim indeed.

Wheels in Motion advised swapping left and right spring to see if the problem follows the spring (which would confirm things I guess).

The other potential cause could be misaligned spring perches. Looking at them closely however they don't look like they've been repaired or replaced and rudimentary measuring with a tape measure didn't highlight any obvious anomalies so if they are out its not by as much as the 15mm height difference we're seeing.

I guess if the spring perch's are at slightly different heights one could get around the problem with differing spring pads but it is a bit worrying why they would be like that in the first place. You'd think manufacturing tolerances would prevent that sort of thing and besides, would I really be the first person to notice this in the ten years of the cars life? It seems far more likely to be some change to the geometry post manufacture that needs to be investigated.

Having nearly been hit in the face on the weekend when removing the springs for the 4th time (and getting too cocky), I'm reluctant to go through that again without the correct spring compressor so I'm thinking of buying this before continuing to tackle the problem.

Laser Coil Spring Compressor For Mercedes Benz 4870 on eBay (end time 29-Mar-10 17:58:53 BST)

Has anyone tried the laser version of this tool? Is it made of cheese or should I throw big money at the proper Klaan alternative?

Also, if I do pinpoint the problem to be the spring perches, can anyone recommend somebody to realign or change the offending spring perch? I am thinking one needs to be particularly careful with this particular job and its best left to someone that is familiar with the task.

 

[grober]

Swapping the springs over would be a good comparison of the 2 springs rating as there will be manufacturing tolerances on them too. However since the problem existed previously and is still there after changing both springs and shock absorbers by logic it points to a problem with something that hasn't been changed! This really only leaves the suspension arms, spring perch height or maybe strut top mounts. You asked "would I really be the first person to notice this in the ten years of the cars life?" and I think I can confidently say yes to that. Perhaps mechanics working on the car might have "noticed in the passing" but since its not their car and it was driving OK why would they bother to mention it? Who knows what "tweaks" are routinely applied to suspension geometry at the manufacturing stage. I was recently reading about a recall on Honda Accords which involves a knocking noise coming from the rear sill area. It was caused by a couple of welded body sections coming into contact due to slight body flexing. The fix --- drive a couple of small plastic wedges between the two sections involved and glue them in place. Will Honda retool their body presses to prevent this in future or use a couple of strategically placed plastic wedges on the production line? I'll give you two guesses.

p.s. genuine laser tools are made by a British based company afaik and seem to be stocked by reputable suppliers Laser Tools | Home

 

[Sp!ke]

Strut top mounts... yes I was looking at these. One of them has a very small crack in the rubber but its so small that I couldnt see that it could be causing this but yes, I'll take them both out for close inspection next time I have the springs off.

I think I've got to lose the new springs anyway, they look like I'm driving a 4x4.

 

[BTB 500]

I think I've got to lose the new springs anyway, they look like I'm driving a 4x4.

Nah, you need ADS for that

 

[nigel cross]

Not sure if possible or wise, but what if you removed the spring both sides, and then put the car down on the grouind to see the difference or not.
That would at least enable you to discount the spring or not.

 

[kth286]

Spike

PM sent.

David

 

[Roger Jones]

"I think you are referring to ther spring pads which I agree could be used as a quick and dirty way to even up the car a bit. I think it is a bit of a bodge though .. as the underlying cause is still present."

Fair comment, but it is a well known and trusted "bodge", and the car is now level. I do intend to replace both springs at the next service.

You ask for recommendations. As you're in west London, SS Motors are not far away in Weybridge.

 

[Sp!ke]

Thanks for all the offers of spring compressors folks - You know who you are, much appreciated.

However I think I'm going to purchase the laser ones as I anticipate I'll be playing around with this for a few weeks as I'll also be fiddling with springs and pads and stuff in a bid to get the car a bit lower.

Very nice gesture though folks, a testament to the good nature and spirit of the forum. :bannana:

 

[Will]

Did you ever get to the bottom of this?

 

[kth286]

Did you ever get to the bottom of this?

Yes - did anything 'spring' to mind ?

 

[chris846]

please bear with me if this has already been covered and I've missed it - but my 124 has eccentric mounts for the bottom wishbones - you can set correct camber with the eccentric 'high' or 'low'....
...or shall I get my coat?
c

 

[Sp!ke]

I'm still fighting this issue.

I took delivery of some spring compressors on Thursday so Thursday night I took the springs and dampers out yet again and swapped them over, just to rule them out. I also replaced the upper shock rubber mounts (one was looking perished) and put in #1 spring pads both sides.

The job was sooo easy with the correct spring compressor

It didn't fix the problem though.

you can set correct camber with the eccentric 'high' or 'low'....

This is an interesting point... the camber has been checked by wheels in Motion and is reasonably ok. Ideally I'd like it perfect but it seemed a waste to spend money on it being done whilst I still had the height issue. Thinking about it though, I suppose the eccentric high and low could make a difference to the ride height, especially if either sides were adjusted on opposite spectrum's in order to get the right camber. In which case, I guess using spring pads to compensate may not be such a bad thing after all. (I think I need an expert to answer that with certainty). I'll climb under the car later to see if the eccentric adjustments differ much each side.

Regardless of the difference in ride height between front and left, these new MB springs make the car sit way too high. I've checked and double checked but they are the right ones for the car according to their markings but I cant live with the way the car sits. Has anyone tried just chopping off a coil of spring before to reduce the ride height? Seeing as I have two sets of springs, I thing I might try this on one set as an experiment.

I was also wondering if uneven rear spring rates could alter the ride height on opposite front wheels. If I compress the offside rear of the car I notice and increase in ride height on the nearside front. (maybe it is the rear springs I should have been looking at and not the fronts)

As you can tell, I'm clutching at straws really here.

 

[LTD]

(maybe it is the rear springs I should have been looking at and not the fronts)

Surely worth a try given the time you have already spent.

 

[GordonTarling]

As you're going to be shortening springs, why not just cut one a little shorter than the other? Not a 'proper' fix, I know, but it'll at least make your car look right.