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2.5-16 Suspension; Why is it soft?
Topic Started: Wed Oct 28, 2009 10:14 pm (1,127 Views)
Michael
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I’ve had the front springs and shocks changed on the 2.5-16 and to my disappointment( when compared to my last car) it’s still soft,

There are no visible leaks on the rear shocks, but could they be weak, but still not leak?
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vaggeli
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worn springs maybe?
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shrekky
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do you have spheres on the front michael ?.................spheres can go in 2 stages..................they become soft and spongy,when they have lost a little bit of gas (this is usual over time,can get away with recharging the sphere) ..........then once they have lost the gas they become rock hard(99% of the time they are knackered)

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vaggeli
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if its got front sls its a very rare car. but also, the spheres have another failure mode shrekky, "trampoline" where they do very minimal shock absorption on only the bottom of the suspensions travel, so ur just "bouncing" on the springs. mine did that, was a shock when we fixed it, the hydraulic fluid drained otu like cream haha, it had gone all horrible creamy/foamy
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Michael
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shrekky
Wed Oct 28, 2009 10:20 pm
do you have spheres on the front michael ?.................spheres can go in 2 stages..................they become soft and spongy,when they have lost a little bit of gas (this is usual over time,can get away with recharging the sphere) ..........then once they have lost the gas they become rock hard(99% of the time they are knackered)

Spheres on rear only.

When I say the car is soft, it's stationary and I'm pressing on the front and rear with the palm of my hand.
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Will
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Remember, there are no rear 'shocks' on a 2.5-16 - they're just hydraulic struts/rams (one of which was replaced by MB at the £3/4k service). It had a fair amount of work on the rear suspension and hydraulic system at that time - some new pipework, diff seals, multi-link arms, bushes etc - it drove pretty tight compared to most other 16 valves I have experienced. Ride height was perfect and the SLS seemed to work very nicely B)

I never felt it was particularly soft, but if you think it is perhaps the rear accumulators should be checked? Or the rear springs. Can't really be anything else to it.

Be interested to hear how you get on.

Will
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Michael
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Will
Wed Oct 28, 2009 10:25 pm
Remember, there are no rear 'shocks' on a 2.5-16 - they're just hydraulic struts/rams Will
If they're not shocks Will, what do they do?
Edited by Michael, Wed Oct 28, 2009 10:44 pm.
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Charles
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Will is right

The spheres do the job of shock absorbing!
Edited by Charles, Wed Oct 28, 2009 11:28 pm.
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Michael
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Charles
Wed Oct 28, 2009 11:27 pm
Will is right

The spheres do the job of shock absorbing, just like the hydraulic system on a Citroen
How do I know if the Spheres are goosed. :ermm:
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gibpetrolhead
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Crashy ride is the symptom. Michael I think you just been driving too much and need a break.
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Michael
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gibpetrolhead
Wed Oct 28, 2009 11:35 pm
Crashy ride is the symptom. Michael I think you just been driving too much and need a break.
Garath, driving is like sex, you can never get too much of it. :lol:

Come to think of it, my ride is a wee bit jittery at the rear.

Replacement spheres, next week then.
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gibpetrolhead
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MICHAEL
Wed Oct 28, 2009 11:39 pm
gibpetrolhead
Wed Oct 28, 2009 11:35 pm
Crashy ride is the symptom. Michael I think you just been driving too much and need a break.
Garath, driving is like sex, you can never get too much of it. :lol:

Come to think of it, my ride is a wee bit jittery at the rear.

Replacement spheres, next week then.
lmao lmao lmao
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Charles
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Michael its a tricky one, I am just about to change my rear spheres on my 2.3 16v because they are rock hard and I are concened the suspension will be too soft when changed, because when I have had new spheres on citroens changed in the past they are at their softest when new.

Do user's on here consider the sls set up too soft?

I will let you know the out come when I put my new spheres on mine next week!

Shrekky
do you have spheres on the front michael ?.................spheres can go in 2 stages..................they become soft and spongy,when they have lost a little bit of gas (this is usual over time,can get away with recharging the sphere) ..........then once they have lost the gas they become rock hard(99% of the time they are knackered)

Cheers Charles
Edited by Charles, Wed Oct 28, 2009 11:43 pm.
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Will
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MICHAEL
Wed Oct 28, 2009 10:40 pm
Will
Wed Oct 28, 2009 10:25 pm
Remember, there are no rear 'shocks' on a 2.5-16 - they're just hydraulic struts/rams Will
If they're not shocks Will, what do they do?
Hi Michael,

The rear struts are just hydraulic rams, they extend and contract with fluid to set the ride height at the rear of the car. The springs partially support the weight of the car, but the height is set hydraulically by the SLS system.

Basically, as you might/might not know, hydraulic fluid cannot be compressed, and so it is impossible for the struts to provide any kind of damping function. The damping is provided by the accumulators at the rear. They have a diaphragm which seperates the two sides of the accumulator - the hydraulic side has the fluid in and there is Nitrogen on the other. As the hydraulic fluid can't be compressed, the diaphragm deflects and the nitrogen is compressed - this gives you the damping at the rear.

If the accumulators are ruptured or if sufficient nitrogen gas has escaped then damping effect will be reduced or non-existant. Hence normally when the accumulators have failed you get a very hard ride at the rear due to there being no travel in the system (a bit like having two fixed rods instead of the struts/shocks fitted at the back - neither will allow any movement.) It's also possible for the amount of nitrogen gas to be reduced compared to new accumulators which would give you a softer ride (less nitrogen = less pressure and therefore more compliance = a softer ride)

In short, check/replace the accumulators - they don't last forever on any car, they're the service-item equivalent of shock absorbers/dampers on normal cars - so with fresh front shocks and new rear accumulators you have effectively got fresh suspension at both ends B)

Will
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Michael
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Will
Wed Oct 28, 2009 11:52 pm
MICHAEL
Wed Oct 28, 2009 10:40 pm
Will
Wed Oct 28, 2009 10:25 pm
Remember, there are no rear 'shocks' on a 2.5-16 - they're just hydraulic struts/rams Will
If they're not shocks Will, what do they do?
Hi Michael,

The rear struts are just hydraulic rams, they extend and contract with fluid to set the ride height at the rear of the car. The springs partially support the weight of the car, but the height is set hydraulically by the SLS system.

Basically, as you might/might not know, hydraulic fluid cannot be compressed, and so it is impossible for the struts to provide any kind of damping function. The damping is provided by the accumulators at the rear. They have a diaphragm which seperates the two sides of the accumulator - the hydraulic side has the fluid in and there is Nitrogen on the other. As the hydraulic fluid can't be compressed, the diaphragm deflects and the nitrogen is compressed - this gives you the damping at the rear.

If the accumulators are ruptured or if sufficient nitrogen gas has escaped then damping effect will be reduced or non-existant. Hence normally when the accumulators have failed you get a very hard ride at the rear due to there being no travel in the system (a bit like having two fixed rods instead of the struts/shocks fitted at the back - neither will allow any movement.) It's also possible for the amount of nitrogen gas to be reduced compared to new accumulators which would give you a softer ride (less nitrogen = less pressure and therefore more compliance = a softer ride)

In short, check/replace the accumulators - they don't last forever on any car, they're the service-item equivalent of shock absorbers/dampers on normal cars - so with fresh front shocks and new rear accumulators you have effectively got fresh suspension at both ends B)

Will
Will, thanks for that valuable information. :D

As it happens I have at hand, almost new Spheres and Hydraulic rams, so I'll start with the Spheres.
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Will
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MICHAEL
Wed Oct 28, 2009 11:58 pm
Will
Wed Oct 28, 2009 11:52 pm
MICHAEL
Wed Oct 28, 2009 10:40 pm
Will
Wed Oct 28, 2009 10:25 pm
Remember, there are no rear 'shocks' on a 2.5-16 - they're just hydraulic struts/rams Will
If they're not shocks Will, what do they do?
Hi Michael,

The rear struts are just hydraulic rams, they extend and contract with fluid to set the ride height at the rear of the car. The springs partially support the weight of the car, but the height is set hydraulically by the SLS system.

Basically, as you might/might not know, hydraulic fluid cannot be compressed, and so it is impossible for the struts to provide any kind of damping function. The damping is provided by the accumulators at the rear. They have a diaphragm which seperates the two sides of the accumulator - the hydraulic side has the fluid in and there is Nitrogen on the other. As the hydraulic fluid can't be compressed, the diaphragm deflects and the nitrogen is compressed - this gives you the damping at the rear.

If the accumulators are ruptured or if sufficient nitrogen gas has escaped then damping effect will be reduced or non-existant. Hence normally when the accumulators have failed you get a very hard ride at the rear due to there being no travel in the system (a bit like having two fixed rods instead of the struts/shocks fitted at the back - neither will allow any movement.) It's also possible for the amount of nitrogen gas to be reduced compared to new accumulators which would give you a softer ride (less nitrogen = less pressure and therefore more compliance = a softer ride)

In short, check/replace the accumulators - they don't last forever on any car, they're the service-item equivalent of shock absorbers/dampers on normal cars - so with fresh front shocks and new rear accumulators you have effectively got fresh suspension at both ends B)

Will
Will, thanks for that valuable information. :D

As it happens I have at hand, almost new Spheres and Hydraulic rams, so I'll start with the Spheres.
Michael,

The accumulators/spheres are a very quick/easy job, just two hydraulic pipes/hoses and two nuts from memory.

Make sure you get some replacement copper washers and some fresh ZH-M fluid, both available from MB for a reasonable price.

It's a half-hour job each side two swap them, probably less on a ramp if it all goes well.

How new are the accumulators you have and are they genuine - they're not fortunes new if you're not sure how good the ones you have are.

Will
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Michael
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Will
Thu Oct 29, 2009 12:02 am
Make sure you get some replacement copper washers and some fresh ZH-M fluid, both available from MB for a reasonable price.

How new are the accumulators you have and are they genuine - they're not fortunes new if you're not sure how good the ones you have are.

Will
Can't say for sure how old they are, but they do look very new, they're genuine MB, as are the Rams.
Would I fit anything else! :D
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Desmoboy
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Very informative post.
I have a 2.5 16 with a very harsh ride, mostly from the rear. See my other recent posts asking questions on here. Much harder ride than my old 2.6
So, i think from the descriptions here that my spheres have probably given up the ghost. When you say not very expensive , what kind of money are we talking about as i think i need to talk to my delaership in the morning.
Thanks
keith
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Nathan
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I have recently ordered some myself, around £105 each.
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stwat
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Desmoboy
Thu Oct 29, 2009 1:39 am
Very informative post.
I have a 2.5 16 with a very harsh ride, mostly from the rear. See my other recent posts asking questions on here. Much harder ride than my old 2.6
So, i think from the descriptions here that my spheres have probably given up the ghost. When you say not very expensive , what kind of money are we talking about as i think i need to talk to my delaership in the morning.
Thanks
keith
The valvers have a much harder ride than the 2.6's. They are a sporty version of the 190 whilst the 2.6 is the luxury version. I have both and they are like chalk and cheese when getting into one from the other. I often love jumping into the 2.6 simply for its plush soft limo style ride.
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Michael
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The spare spheres that I have look like new, but is there a way of testing them?
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Big Ben
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MICHAEL
Thu Oct 29, 2009 1:18 pm
The spare spheres that I have look like new, but is there a way of testing them?
No Mate. The only thing to do is put them on the car and see!

Dont forget that the sls valve can also cause a soft wallowy ride if its worn or not set properly.
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Michael
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Big Ben
Thu Oct 29, 2009 2:51 pm
MICHAEL
Thu Oct 29, 2009 1:18 pm
The spare spheres that I have look like new, but is there a way of testing them?
No Mate. The only thing to do is put them on the car and see!

Dont forget that the sls valve can also cause a soft wallowy ride if its worn or not set properly.
Thanks Brian. :D
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cossie connoisseur
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there can be only one ;-)
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yeah i couldnt be arsed to doagnose mine so changed the lot......was a smart move in my head, not such a smart move on my wallet!!!
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bolide
Bolide
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MICHAEL
Wed Oct 28, 2009 10:24 pm
When I say the car is soft, it's stationary and I'm pressing on the front and rear with the palm of my hand.
How does it drive? How it feels when stationary is not really relevant to how it works dynamically

When I bought my 944 I was convinced it didn't go round corners because it was so soft. It actually cornered brilliantly - there was just more body roll that I was used to

The ARBs make a huge difference to the way the car handles. Make sure all the ARB bushes are replaced and that there is no wear in any suspension links before condemning anything

Nick Froome
www.w124.co.uk
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Michael
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bolide
Thu Oct 29, 2009 10:20 pm
MICHAEL
Wed Oct 28, 2009 10:24 pm
When I say the car is soft, it's stationary and I'm pressing on the front and rear with the palm of my hand.
How does it drive? How it feels when stationary is not really relevant to how it works dynamically

When I bought my 944 I was convinced it didn't go round corners because it was so soft. It actually cornered brilliantly - there was just more body roll that I was used to

The ARBs make a huge difference to the way the car handles. Make sure all the ARB bushes are replaced and that there is no wear in any suspension links before condemning anything

Nick Froome
www.w124.co.uk
Nick, It drives great, but I do have the feeling that it's a bit jittery at the back.
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Nathan
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Does it raise when loaded? If not ARB valve. ;)
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Michael
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Nath_XPR
Fri Oct 30, 2009 1:08 am
Does it raise when loaded? If not ARB valve. ;)
Nope, but I just know there's something quite right, so a change of Spheres, should do the the trick.
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Michael
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Had the spheres replaced yesterday by Merc-Tech.

There's more to it than I imagined. Car up on the ramp, , the hydraulic pipes have to be released, one side at a time to let the fluid drain off, then the old sphere is removed and the new one fitted, same procedure for the other side.

Ramp lowered; add a good dose of new fluid raise the ramp and start to bleed the system until the knocking stops, then check and adjust the ride height valve.

Car off the ramp and the result is; a different car altogether, now with a nice tight **insert swear word here**. :driver:
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gibpetrolhead
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Glad the **insert swear word here** is fixed on more wiggling!!. :lol:
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stwat
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Good stuff, Michael :)

Refurbing my sls was the best thing i ever did to mine. :)

Does it now feel as good as the EVO did?
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Michael
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stwat
Wed Nov 25, 2009 10:57 pm
Good stuff, Michael :)

Refurbing my sls was the best thing i ever did to mine. :)

Does it now feel as good as the EVO did?
Nothing feels as good as an Evo1, Evo11's excepted of course. :lol:
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stwat
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MICHAEL
Wed Nov 25, 2009 11:05 pm
stwat
Wed Nov 25, 2009 10:57 pm
Good stuff, Michael :)

Refurbing my sls was the best thing i ever did to mine. :)

Does it now feel as good as the EVO did?
Nothing feels as good as an Evo1, Evo11's excepted of course. :lol:
Fair comment :lol:
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Michael
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shrekky
Wed Oct 28, 2009 10:20 pm
spheres can go in 2 stages, they become soft and spongy, when they have lost a little bit of gas (this is usual over time,can get away with recharging the sphere) then once they have lost the gas they become rock hard(99% of the time they are knackered)

As ever Shrekky, your'e on the money. :lol:
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