w124 rear shocks and other bits!

[ric220]

Hi there - am new to the forum but hope you can help...
Have bin told I need a new rear shock on my 220TE ('93). I live nr Brighton and GCS in Horsham have quoted £340 to replace (1)!! I know they're self-levelling and therefore complex but does anyone know a decent but cheaper specialist in my area? Also, I'd like to get rid of the steel 15" wheels and replace with some replica alloy 16"'s I've just been given - I assume there's plenty of space for this size "underneath the arches" (I suspect 17" or even 18" would fit).
Many thanks for your advice!

 

[Bolide]

TE rear suspension

There are no shock absorbers on the back of a TE. There are two hydraulic struts driven by the self-levelling system. The damping is provided by two suspension spheres. The whole system is like a Citroen BX with the addition of 2 springs. The struts only need replacing if worn / leaking

I'd try Alan Robertson (Hove) on 01273 770838 or Ian at Thwaites (Portslade) on 01273 430303. Both know these cars well and I've used them and come away happy

Martin at Alan's workshop is a Citroen man and won't have any problem at all with diagnosing & repairing hydraulic rear suspension

There are so many of these cars around that any Mercedes specialist should be able to do this job in their sleep. It's the backstreet garages with no experience that struggle. That's not to say that GCS in Horsham aren't 100% accurate with their diagnosis & estimate


Nick Froome
www.w124.co.uk

 

[clive williams]

Hi there - am new to the forum but hope you can help...
Have bin told I need a new rear shock on my 220TE ('93). I live nr Brighton and GCS in Horsham have quoted £340 to replace (1)!! I know they're self-levelling and therefore complex but does anyone know a decent but cheaper specialist in my area? Also, I'd like to get rid of the steel 15" wheels and replace with some replica alloy 16"'s I've just been given - I assume there's plenty of space for this size "underneath the arches" (I suspect 17" or even 18" would fit).
Many thanks for your advice!

Ric,

The price of £340 splits about 50/50 wholesale price parts and labour/profit on parts for one side only. The unit is a damper as well as a hydraulic self leveller and I would recommend replacement of both sides at once as having dampers of different damping rates on each side - worn/new - is not good. they are relatively easy to install so its not out of the way for a competent DIYer. That way you will do both for about the same price as one garage fit. You are unfortunately caught between a rock and a hard place because the alternative is to replace the units with standard shock absorbers but that will involve an amount of engineering to remove the self levelling pump as its driven by the auxillary belt. The potential costs of a change could equal the costs of replacement.

With regard to the wheels - what size are they? Look on the inside face of the wheel where the size is probably stamped on one of the spokes as say, 7Jx16 H2 ET41. The width of the wheel (the J no.) and the offset (the ET no.) will give a fighting chance to tell if they will fit and recommend a suitable tyre size. With the 16" wheels you will probably be fitting 55 profile tyres and with a 17" a 45 profile tyre. I consider 50% aspect ratio as the bottom limit of my tyre choice as there are no performance advantages below that ratio. The only reason for lower profiles is fashion but in fitting the fashion item you compromise the other tyre attributes.

Clive

500E
E320CDIT210

 

[andy_k]

sorry clive, but I think you are wrong there, the struts are not dampers, the spheres are.

Replacing one strut is therefore perfectly acceptable

HTH

Andy

 

[clive williams]

sorry clive, but I think you are wrong there, the struts are not dampers, the spheres are.

Replacing one strut is therefore perfectly acceptable

HTH

Andy

I though the spheres were the spinging medium as they are in the Citroen, that are in addition to the main road springs. They act as pressure accumulators, the pressure of which is modulated to maintain the ride height. The damping mechanism is as in the Citroen system in the strut.

Clive

500E
E320CDIT210

 

[andy_k]

when the spheres fail you lose damping - the things bounce around all over the place

 

[ennio]

if you want specialist advice on W124, you must be near http://w124.co.uk/
[Edit]
Just noticed Nick Froome has earlier responded to your post; expect he knows what he is talking about

 

[clive williams]

when the spheres fail you lose damping - the things bounce around all over the place

Andy,

Yes of course it does. The spheres are charged with the hydraulic fluid, which pressurises the nitogen in the strut damper. If you loose that fluid pressure then the damper fluid is no longer under pressure and can't damp.

Clive

500E
E320T210

 

[andy_k]

hmmmm,

Clive,

The struts are filled with hydraulic fluid by the self levelling pump by way of the self levelling valve on the rear anti roll bar, which as the piston inside them moves up and down fluid is transferred back to the spheres (these spheres have a thick rubber diaphragm which keeps the nitrogen and hydraulic fluid seperate). If you need further confirmation on the function of these struts then take one off the car, when it's emptied of all it's fluid it moves freely and easily unlike a shock absorber which offers resistance. The self levelling valve controls the flow of fluid to the struts to maintain the vehicles ride height when heavy loads are being carried.

The gas and fluid are crucial, whereas you can compress a gas a fluid will keep a constant volume. so, the gas (nitrogen) becomes the spring (assisted by the road springs) and the fluid provides the damping.

HTH

Andy

Well, at least that's how it works on a W124

 

[clive williams]

hmmmm,

Clive,

The struts are filled with hydraulic fluid by the self levelling pump by way of the self levelling valve on the rear anti roll bar, which as the piston inside them moves up and down fluid is transferred back to the spheres (these spheres have a thick rubber diaphragm which keeps the nitrogen and hydraulic fluid seperate). If you need further confirmation on the function of these struts then take one off the car, when it's emptied of all it's fluid it moves freely and easily unlike a shock absorber which offers resistance. The self levelling valve controls the flow of fluid to the struts to maintain the vehicles ride height when heavy loads are being carried.

The gas and fluid are crucial, whereas you can compress a gas a fluid will keep a constant volume. so, the gas (nitrogen) becomes the spring (assisted by the road springs) and the fluid provides the damping.

HTH

Andy

Well, at least that's how it works on a W124

Andy,

I agree in general with all of that but the original query was regarding the replacement of the strut. I still contend that the strut is the damper in the rear suspension. For confirmation check out your Haynes Manual for the W124, Section 10.12 Suspension & Steering #17 para1-5. Haynes specifically calls the strut the "shock absorber" i.e. damper.
As with any damper/shock absorber they damp the motion of the spring/vehicle by passing fluid through a series of holes, the number and size of these holes determines the damper rate. Seals ensure that the fluid goes where it should together with various valves. All these seals and valves wear from the day they are installed and used, that is the reason the damper manufacturers strongly recommend replacement of damper in pairs so as not to imbalance the handling characteristics from side to side. Indeed, there is a valid argument that all dampers are replaced when one fails to maintain the relative handling balance between all wheels. However, economics then come into it.
The fact that the system is self levelling with a pressurised hydraulic supply does not mitigate against the wear in the damper.
As an aside, I have always thought that the Mercedes system appears on the face of it as a half a***d system since they could have very easily dispensed with the coil springs on the rear and used the nitrogen pressure in the accumulators as the full spring in the way Citroen do. Then, its a short step providing a four wheel hydropneumatic suspension. Then there is full high pressure braking..........

Clive

500E
E320CDIT210

 

[Bolide]

W124 rear suspension

As far as I know the suspension strut at the rear of a W124 has no damping mechanism and, as such, can't be called a damper. What Haynes refer to it as is, to my mind, irrelevant

I suspect the reason Mercedes used springs at the rear was to apply a belt & braces approach. A BX with no fluid will drag it's tail along the ground - quite literally - and I suspect the clever engineers at Mercedes wanted to avoid such an embarrassing situation

Whatever the technical merits of the system I'm sure (or fairly sure...) we can all agree that it's an elegant solution to a problem and that the result, from a handling point of view, is superb


Nick Froome
www.w124.co.uk

 

[turnipsock]

As far as I know the suspension strut at the rear of a W124 has no damping mechanism and, as such, can't be called a damper.

so where does the damping come from? if there was no damping, the thing would hop all over the place.

MB have put in springs on top the citroen stuff, this has the advantage that the back end doesn't sink down after the pressure drops.

The other clever bit is that the rear end will self level.

Citroens don't have springs so can pump up the fluid side to any level. They can lift themselves up and down, which releaves boredom in traffic jams. You don't need to wind up a jack to replace a tyre. With all the modern electonic stuff, you can even get a car that sits level when cornering.

In Citroens, the spheres are both the spring and the damper.

I love the smell of nitrogen in the morning

 

[andy_k]

so where does the damping come from? if there was no damping, the thing would hop all over the place.

there are no physical dampers as I've been trying to say

the friction of the hydraulic fluid as it moves around the pipes which are of specific interior dimensions and construction (the rear axle pipes have a spiral insert in them) provides the damping.

Clive, quoting the Haynes manual - Their description of the system is wrong as is so much of the stuff printed in these guides

Just as my final comment on this, I spoke to my local stealership service department today and I quote them "No problem sir you can replace either hydraulic strut on it's own. They are not like shock absorbers but you must change the spheres in pairs."

HTH

Andy