I know that Xantia suspension and general hydraulic problems have been done to death on this forum but I REALLY would appreciate advice on my hard Xantia suspension. Having read many previous postings about hard suspension unless it was just a change of spheres there seems to be no particular cure. Everyone seems to have had different symptoms and different ways to cure the problem. The car is 1995 TDSX 85,000m. When I bought the car three years ago the suspension was rather firm then. I fitted four corner spheres and new accumulator sphere. This did the trick, although it's never been what I would have called the legendary magic carpet ride as others have described, but it was much better and I lived with that ok. About a year ago now I felt that the suspension had been getting gradually just a little firmer. Certainly not as bad as before the new spheres were fitted though. By this time the spheres had only done about 18,000miles so I ruled those out. I drained the LHM tank cleaned the filters and refilled with fresh LHM. The old LHM whilst discoloured certainly wasn't the gungy brown that others have described. I bled this through the brake lines also and bled excess air from the system. This didn't really make a great deal of difference to the ride but I thought I'd try it for a while to see if it would settle down. After about a month with no difference I bought four more new spheres. Fitted these but found that it made little difference. These spheres have only done around 8,000miles now so they should be ok. Since then the ride has become progressivly worse. Last week I had a look at the height correctors and gave them a real good soaking in WD40 and spray grease whilst moving the lever through it's range for a long while and I'm sure that they are moving freely and not the cause of the problem. When starting from cold the stop lights go out in about 15 seconds which I'm sure is ok. The suspension rises but does so quite slowly. The supension will rise and lower ok when set by the lever. The height correctors appear to be doing their job, when I put any weight on the front or rear the supension drops then rises back to the correct level. When the weight is removed it rises up then after a few seconds settles back level again. I also tow a caravan and having this hitched also works the rear suspension ok. Whilst pushing down on any corner of the car it does have suspension travel and movement so it's by no means solid. Certainly not like the solid feel of worn spheres. When driving along a fairly smooth road the car feels ok, it's just on rough road surfaces that the suspension feels like it's bottoming out but I don't think it is. With engine running and the car standing level the ride height seems to be ok. I know, I'm sorry , this is going on a bit and I could probably keep going on trying to describe the harsh, rough ride. I haven't changed the anti-sink sphere but from what I've read on previous postings it makes no difference to the ride, only stopping rear of the car from sinking. I also haven't flushed the system with hydraflush. I've also seen various good and bad reports from using hydraflush and wonder if it is worth trying that. Being unemployed at the present time and money being a bit tight I'm not able to go through the route of trying this and trying that until I find a solution so I WOULD BE MOST GRATEFUL for ANY advice or tips regarding my rough riding Xantia.
DEN
Xantia Suspension Again ! (sorry)
Moderator: RichardW
Dear Den !
Being un-employed myself, I can figure out your situation.
ONLY these problems causes hard suspension :
1) flat wheel spheres
2) lo-profile tyres, wrong (high) inflated tyres
3) shot rear arm bearings
4) dry front strut slide bearings
5) wrong spec spheres
6) wrong driving height
7) air in suspension system
8) defective or severe dirty suspension cylinders
9) Activa system !! (born hard !!)
10) electronics & cabling in hydractive systems.
Comments on hard suspension causes :
1) evident
2) evident
3) shot rear arm bearings tends to bind, in severe cases can totally lock rear arms in (any) posistion. If suspected immediate attention is required, since the shot bearings WILL destroy bearing housing in the rear arm. A new arm is then only remedy. To test the bearing, antirollbar must be unscrewed from arm, to allow for free movement test.
4) this is quite common, and not known to most (Cit !!) garages. The problem is in fact a premature indication of worn front struts. The slide bearing wears and causes allowance for sidewards movement in the front struts. This in turn can make the front struts bind more or less. Only effective cure is replacement of the strut. A good life prolonging cure, is to grease the shiny strut rod, found under the upper protection gaiter. Use ONLY heavy (ballbearing) grease.
5) spheres are designed for the exact model and axle end, according to weight, load capacity & max speed of car. The small hole found in the middle of the sphere base, resembles the shock absorber action. The bigger the hole, the less damping. The PRESSURE of the sphere counteracts the expected average load on the wheel. The VOLUME of the sphere resembles the lenght of a "standard" coil spring. As a rule of thumb, a bigger damper hole gives softer suspension, on behalf of hi-speed stability (more instant leaning & roll).
6) wrong driving height offsets the geometri in the suspension.
7) air in system is ABSOLUTELY unwanted. It gives uncontrolled suspension action since common air is VERY flexible. Upsets the spheres action, and clearly feels as bumpy & hard suspension.
NOTE 1 : Check the filter mesh's in the reservoir. If cracks or holes, the normal air bubbles from return hoses, escapes directly into the pump's suction hose, introducing air in the system. Besides filtering dirt, the fine mesh in the filters also breaks down the air bubbles.
NOTE 2 : Check the pump's suction hose for tightness on both reservoir & pump studs. Also check hose for cracks. A leaking hose is NEVER seen, since the pump sucks on the hose. Instead air gets into the pump from the hose. A common garden PVC water hose (clean !!) works excellent as quick spare.
8) dirt collects in every dead end in the system, since there's no through flushing of LHM oil.
9) evident. Common cause of bad Xantia repute.
10) poor quality in electrics system is unfortunately a mark on french cars in general.
These components do NOT cause hard suspension, but causes other (even severe) problems :
1) Anti-sink & accumulator spheres
2) Height correctors, pump & safety valve
3) Dirty LHM
4) leaking pipes, hoses, components
Comments :
1) flat Antisink sphere is commonly indicated by a sudden drop in height, when car is started. But do'nt mix up things. Antisink normally does not work after several days rest on car.
2) these components causes reluctance of gaining the correct height.
3) dirty LHM is a danger to controlling elements, since the dirt causes wear in the ultra precise valve bores, even causes blocking of valve functions. LHM systems are REQUIRED to have the LHM replaced every 60Kkm/38Kmiles. Not because the LHM wears, but simply to remove the dirt TOGETHER with the LHM. Hydraquinage cures are quite effective, since this fluid is designed to loosen all kinds of sediments (dirt) captured in the LHM oilskins everywhere in system. A Hydraquinage cure is recommanded every 3 LHM replacements.
Hydraquinage can NOT cure problems, where foreign matters has stucked components. This is true for instance on the PAS FD valve, where nylon sediments from burst microfilters upsets the servo steering.
4) only leaks causing severe pressure drop, may influence suspension directly. But then you certainly also face the problem of NOT gaining height.
Different brands of LHM oil has NO influence. Anything else is pure religion. NOT facts.
Being un-employed myself, I can figure out your situation.
ONLY these problems causes hard suspension :
1) flat wheel spheres
2) lo-profile tyres, wrong (high) inflated tyres
3) shot rear arm bearings
4) dry front strut slide bearings
5) wrong spec spheres
6) wrong driving height
7) air in suspension system
8) defective or severe dirty suspension cylinders
9) Activa system !! (born hard !!)
10) electronics & cabling in hydractive systems.
Comments on hard suspension causes :
1) evident
2) evident
3) shot rear arm bearings tends to bind, in severe cases can totally lock rear arms in (any) posistion. If suspected immediate attention is required, since the shot bearings WILL destroy bearing housing in the rear arm. A new arm is then only remedy. To test the bearing, antirollbar must be unscrewed from arm, to allow for free movement test.
4) this is quite common, and not known to most (Cit !!) garages. The problem is in fact a premature indication of worn front struts. The slide bearing wears and causes allowance for sidewards movement in the front struts. This in turn can make the front struts bind more or less. Only effective cure is replacement of the strut. A good life prolonging cure, is to grease the shiny strut rod, found under the upper protection gaiter. Use ONLY heavy (ballbearing) grease.
5) spheres are designed for the exact model and axle end, according to weight, load capacity & max speed of car. The small hole found in the middle of the sphere base, resembles the shock absorber action. The bigger the hole, the less damping. The PRESSURE of the sphere counteracts the expected average load on the wheel. The VOLUME of the sphere resembles the lenght of a "standard" coil spring. As a rule of thumb, a bigger damper hole gives softer suspension, on behalf of hi-speed stability (more instant leaning & roll).
6) wrong driving height offsets the geometri in the suspension.
7) air in system is ABSOLUTELY unwanted. It gives uncontrolled suspension action since common air is VERY flexible. Upsets the spheres action, and clearly feels as bumpy & hard suspension.
NOTE 1 : Check the filter mesh's in the reservoir. If cracks or holes, the normal air bubbles from return hoses, escapes directly into the pump's suction hose, introducing air in the system. Besides filtering dirt, the fine mesh in the filters also breaks down the air bubbles.
NOTE 2 : Check the pump's suction hose for tightness on both reservoir & pump studs. Also check hose for cracks. A leaking hose is NEVER seen, since the pump sucks on the hose. Instead air gets into the pump from the hose. A common garden PVC water hose (clean !!) works excellent as quick spare.
8) dirt collects in every dead end in the system, since there's no through flushing of LHM oil.
9) evident. Common cause of bad Xantia repute.
10) poor quality in electrics system is unfortunately a mark on french cars in general.
These components do NOT cause hard suspension, but causes other (even severe) problems :
1) Anti-sink & accumulator spheres
2) Height correctors, pump & safety valve
3) Dirty LHM
4) leaking pipes, hoses, components
Comments :
1) flat Antisink sphere is commonly indicated by a sudden drop in height, when car is started. But do'nt mix up things. Antisink normally does not work after several days rest on car.
2) these components causes reluctance of gaining the correct height.
3) dirty LHM is a danger to controlling elements, since the dirt causes wear in the ultra precise valve bores, even causes blocking of valve functions. LHM systems are REQUIRED to have the LHM replaced every 60Kkm/38Kmiles. Not because the LHM wears, but simply to remove the dirt TOGETHER with the LHM. Hydraquinage cures are quite effective, since this fluid is designed to loosen all kinds of sediments (dirt) captured in the LHM oilskins everywhere in system. A Hydraquinage cure is recommanded every 3 LHM replacements.
Hydraquinage can NOT cure problems, where foreign matters has stucked components. This is true for instance on the PAS FD valve, where nylon sediments from burst microfilters upsets the servo steering.
4) only leaks causing severe pressure drop, may influence suspension directly. But then you certainly also face the problem of NOT gaining height.
Different brands of LHM oil has NO influence. Anything else is pure religion. NOT facts.
Like Anders said, worn rear arm bearings certanly affects the ride quality, like in my BX. Interestigly, there were no free play and no wheel slant (yet), but the suspension was somewat stiff. Rear end should dive when you push the bumper with small force, maybe 1-2 kg - it should feel VERY smooth. If not, arm bearings are under suspect (well, the things are different on HA equipped Xantias - the damping seems to be higher even in soft mode, so it's hard to test it this way).
About the air in the system, when changing spheres, some air allways gets trapped in suspension cylinders, even after 'cytrobics', but it should drift out (thorough the return pipes) in a few days. So the ride is even smoother at first, because the damping is lower, but feels somewhat 'underdamped'.
About the sphere pressure and voulme, bigger the product pressure x volume, lower the vehicle's 'eigen frequency'. If that frequency is too high (old spheres), the ride is bouncy.
About the dampers, as I said several times, small central bore is not very important, except on very slow vertical movements, because other 8 holes around it are much bigger (3-4 mm in diameter). They are covered with steel discs. Thicker the discs, higher the damping. If the damping is high, the ride is harsh. But if the damping is too low, the ride will also be bouncy from time to time, because suspension arms will be hitting bounce and rebound stops.
About the air in the system, when changing spheres, some air allways gets trapped in suspension cylinders, even after 'cytrobics', but it should drift out (thorough the return pipes) in a few days. So the ride is even smoother at first, because the damping is lower, but feels somewhat 'underdamped'.
About the sphere pressure and voulme, bigger the product pressure x volume, lower the vehicle's 'eigen frequency'. If that frequency is too high (old spheres), the ride is bouncy.
About the dampers, as I said several times, small central bore is not very important, except on very slow vertical movements, because other 8 holes around it are much bigger (3-4 mm in diameter). They are covered with steel discs. Thicker the discs, higher the damping. If the damping is high, the ride is harsh. But if the damping is too low, the ride will also be bouncy from time to time, because suspension arms will be hitting bounce and rebound stops.
Thanks so far, Anders and Alexx, for the info. I don't think there is any great problem with the rear arm bearings to cause the rough ride as the ride is rough front and rear. If anything the ride may be slightly worse on the front, but it generally seems to affect the whole car. With regard to one of your suggestions, Anders, regarding ride height although the ride height looks ok visually is it possible for it to change over time and maybe not notice too much? I know that in the Haynes manual it gives figures for ride height but what would be an approximate measurement between tyre to wheel arches? My tyres are 185/65x15 and I stick to the recommended pressures. I know that the height corrector linkage is connected to the rollbar, so if the height needed adjustment would this be done by altering the position on the rollbar? I have a pit in my garage so I am able to work under the car in safety.
DEN
DEN
Den :
You're spot on.
Loosening the clamp on the rollbar, then turn the clamp, adjusts the selv levelling ride height. But CAREFULL. Some 1:5 ratio on height setting from clamp position on rollbar. Small adjustments only ! Avoid the clamp is dangling loose. Leave it clamped such, that light knocking with a small hammer or large screwdriver, can barely move it.
Anything else is hard to control.
Allways jerk the suspension after each setting, to release any small binding and let it settle, to test new height.
A rule of thumb is to look at the driveaxles. They should be close to level with ground, slightly dropping at the wheel ends.
I donno if the 3-finger BX front wheelarch test is valid for the Xantia.
You have to look around at parking lots, or discuss with owners/garages.
Alex :
Have you actually seen a disassembled valve assembly from the sphere mount ? I remember seen a series of pic's of this on a Japanese site, ca'nt find the URL again though.
I allways assumed that the center bore, was the "wheel-moving-up-into-wheelarch" damper valve, and the disc valve then simply opens for more rapid LHM out-flow on the wheel's down bounce.
This is the best and most logic way I can understand the function, since this would resemble the function of a standard shock absorber. Adjusting (drilling up) the center bore, in fact VERY distinctly soften the suspension by own experience. This I tried several y's ago after some discussions with BX owners who had come up with this idea.
The ride was NEVER bouncy, in fact close to a DS I tried many y's ago, and have missed ever since. My CX is close, could even be closer if the same mod was done.
It is possible at least on older types of spheres I've seen, to totally remove the damper valve bits, resembling a no-damping accumulator sphere. In fact the center bore resembles a simple screwed-in (brass) bolt drilled through.
It's been a while I've had a look on a sphere base, and then only the more or less flat ones I have on stock. (still planning building my own, NON-valve insert re-gasser, but that's a totally different story).
You're spot on.
Loosening the clamp on the rollbar, then turn the clamp, adjusts the selv levelling ride height. But CAREFULL. Some 1:5 ratio on height setting from clamp position on rollbar. Small adjustments only ! Avoid the clamp is dangling loose. Leave it clamped such, that light knocking with a small hammer or large screwdriver, can barely move it.
Anything else is hard to control.
Allways jerk the suspension after each setting, to release any small binding and let it settle, to test new height.
A rule of thumb is to look at the driveaxles. They should be close to level with ground, slightly dropping at the wheel ends.
I donno if the 3-finger BX front wheelarch test is valid for the Xantia.
You have to look around at parking lots, or discuss with owners/garages.
Alex :
Have you actually seen a disassembled valve assembly from the sphere mount ? I remember seen a series of pic's of this on a Japanese site, ca'nt find the URL again though.
I allways assumed that the center bore, was the "wheel-moving-up-into-wheelarch" damper valve, and the disc valve then simply opens for more rapid LHM out-flow on the wheel's down bounce.
This is the best and most logic way I can understand the function, since this would resemble the function of a standard shock absorber. Adjusting (drilling up) the center bore, in fact VERY distinctly soften the suspension by own experience. This I tried several y's ago after some discussions with BX owners who had come up with this idea.
The ride was NEVER bouncy, in fact close to a DS I tried many y's ago, and have missed ever since. My CX is close, could even be closer if the same mod was done.
It is possible at least on older types of spheres I've seen, to totally remove the damper valve bits, resembling a no-damping accumulator sphere. In fact the center bore resembles a simple screwed-in (brass) bolt drilled through.
It's been a while I've had a look on a sphere base, and then only the more or less flat ones I have on stock. (still planning building my own, NON-valve insert re-gasser, but that's a totally different story).
He, he, this sphere dampers are really mysterious. I examined (didn't disassemble) old spheres from father's GSA (definitively genuine - they came with the car when new), found somewhere in the garage. There were also pictures of a disassembled sphere on a Japanese site, but it seems it's no longer active. Front sphere from GS has central bore 1.3-1.4 mm, and other bores cca 3 mm in diameter, covered with 2 steel plates on each side (outside for extension, inside for compression). Rear sphere has central bore 0.8-0.9 mm and other bores cca 4 mm, covered with 3 steel plates, thickness of each is 0.2-0.3 mm (these measurements are estimates).
What's also interesting, front spheres for GS have specified bore 1.8 mm, and rear 1.1 mm. Weird.
Rear spheres on my BX had about twice thicker plates than GS's, so the damping was obviously much higher (maybe wrong type, who knows). Now, with GS spheres on the rear, the ride is much smoother.
Central bore is not enough because, according to physical laws, the damper would have 'progressive' characteristic - twice higher wheel's vertical speed would mean 4 times higher damping force. So the car would fall apart on sharper road irregularities, where wheel's vertical speed can be more than 1 m/s, or would be too underdamped on longer road 'waves', where vertical speed is very low. So there are other bores. Higher the wheel speed, higher the pressure, plates deflects more, uncovering bores. And so we have approximately linear characteristic wheel's speed-damping force. It's the same story on conventional dampers.
Because of stiffer springs, cars with conventional suspension have smaller 'central bores', but plates over other bores are thinner. Hence, low-speed damping is higer, and there's no famous 'citroen magic carpet'. On the other side, high-speed damping is lower, so there's no not-so-famous 'citroen harshness' on really bad surfaces (especially when the dampers are little older).
If you drill central bore, the ride will be little more floaty, but on sharper bumps there will be very little improvement (this is theoretically - didn't try it). So I don't find it useful, although some mechanics here are also doing that, making 'comfort spheres'. Or so they think.
Den:
It's possible that the ride height is not correct, because after several years the linkage can be a little deformed (at least that's what happened on father's GS). The most simple way to check the ride height is this one: measure the height of the wheel arch in minimum and maximum position. Correct height in normal driving position is in the middle of that, minus 5 mm on the front / 10 mm on the rear, with the tolerance +/- 8 mm. It's the same on all citroen vehicles with hydraulics (except maybe C5).
What's also interesting, front spheres for GS have specified bore 1.8 mm, and rear 1.1 mm. Weird.
Rear spheres on my BX had about twice thicker plates than GS's, so the damping was obviously much higher (maybe wrong type, who knows). Now, with GS spheres on the rear, the ride is much smoother.
Central bore is not enough because, according to physical laws, the damper would have 'progressive' characteristic - twice higher wheel's vertical speed would mean 4 times higher damping force. So the car would fall apart on sharper road irregularities, where wheel's vertical speed can be more than 1 m/s, or would be too underdamped on longer road 'waves', where vertical speed is very low. So there are other bores. Higher the wheel speed, higher the pressure, plates deflects more, uncovering bores. And so we have approximately linear characteristic wheel's speed-damping force. It's the same story on conventional dampers.
Because of stiffer springs, cars with conventional suspension have smaller 'central bores', but plates over other bores are thinner. Hence, low-speed damping is higer, and there's no famous 'citroen magic carpet'. On the other side, high-speed damping is lower, so there's no not-so-famous 'citroen harshness' on really bad surfaces (especially when the dampers are little older).
If you drill central bore, the ride will be little more floaty, but on sharper bumps there will be very little improvement (this is theoretically - didn't try it). So I don't find it useful, although some mechanics here are also doing that, making 'comfort spheres'. Or so they think.
Den:
It's possible that the ride height is not correct, because after several years the linkage can be a little deformed (at least that's what happened on father's GS). The most simple way to check the ride height is this one: measure the height of the wheel arch in minimum and maximum position. Correct height in normal driving position is in the middle of that, minus 5 mm on the front / 10 mm on the rear, with the tolerance +/- 8 mm. It's the same on all citroen vehicles with hydraulics (except maybe C5).
-
Dave Burns
- Posts: 1915
- Joined: 14 May 2001, 05:30
- Location: United Kingdom
- My Cars:
- x 2
Just an observation on those bore sizes Alex, it probably depends on how much oil is going to be forced through them, for instance, the pistons in the front struts are directly driven, so 10mm of wheel travel = 10mm of piston travel.
The rear pistons aren't driven at the same 1:1 ratio as the fronts, thus less oil will be displaced for the same amount of wheel travel, this theory assumes similar cylinder daimeters though.
It could also explain why the pressure in the spheres are so much lower at the rear, and probably not simply down to the weight of the engine.
Dave
The rear pistons aren't driven at the same 1:1 ratio as the fronts, thus less oil will be displaced for the same amount of wheel travel, this theory assumes similar cylinder daimeters though.
It could also explain why the pressure in the spheres are so much lower at the rear, and probably not simply down to the weight of the engine.
Dave
Before you adjust the height corrector just pause a moment and think if the hydraulic pressure seems ok. The reason I say this is that my BX had always seemed a bit harsh but also suffered from low pressure due to a faulty power steering splitter and I think the effect was that the ride height dropped a bit while the car was being driven. I have now cured the problem and the ride is much better and I can now join everyone else and look for perfection!
Certainly on a BX the height is measured between the ground and the cross memebers. To save getting underneath with the engine running and the car at the travelling height (practically impossible) why not make a measure from a piece of wood long enough to be poked under the subframe with another piece at right angles and marked with the correct height and another mark say 1 inch lower. You should then be able to measure the height easily and see if there is any need for adjustment.
just another thought - how well are your bottom swivels and drop links lubricated. It they are aged and the grease has dried up they will contribute to a harsh ride.
jeremy
Certainly on a BX the height is measured between the ground and the cross memebers. To save getting underneath with the engine running and the car at the travelling height (practically impossible) why not make a measure from a piece of wood long enough to be poked under the subframe with another piece at right angles and marked with the correct height and another mark say 1 inch lower. You should then be able to measure the height easily and see if there is any need for adjustment.
just another thought - how well are your bottom swivels and drop links lubricated. It they are aged and the grease has dried up they will contribute to a harsh ride.
jeremy
Dave, your observation is correct.
On GS and CX, things are similar front and rear. Pistons have internal diameter 35 mm, and they are driven at approximately the same ratio - about 1:3. But front suspension takes more weight, so the sphere pressure is different, and dampers are differently tuned (by different combination of bore diameters and steel plates).
On BX, Xantia and XM, rear pistons are also 35 mm (some models 38 or 40, I think), and they are also driven at ratio somewhere around 1:3. Front pistons are driven at 1:1 ratio, but they have smaller diameter (I think it's 22 mm on Xantia MkI, other models probably similar), so the quantity of displaced LHM is only about 20% higher for the same movement of the wheel.
On GS and CX, things are similar front and rear. Pistons have internal diameter 35 mm, and they are driven at approximately the same ratio - about 1:3. But front suspension takes more weight, so the sphere pressure is different, and dampers are differently tuned (by different combination of bore diameters and steel plates).
On BX, Xantia and XM, rear pistons are also 35 mm (some models 38 or 40, I think), and they are also driven at ratio somewhere around 1:3. Front pistons are driven at 1:1 ratio, but they have smaller diameter (I think it's 22 mm on Xantia MkI, other models probably similar), so the quantity of displaced LHM is only about 20% higher for the same movement of the wheel.
Alex :
This is the best explanation on the Sphere damper valve function, I've ever read [^]
Your submission is now stored as reference material on my HD [8D]
But still - it's a bit duff on the steel plate disc valve issue.
The thickness of the discs [?]
Has it to do actually with the weight of these discs, then this way adjusting the disc valve action [?]
This is the best explanation on the Sphere damper valve function, I've ever read [^]
Your submission is now stored as reference material on my HD [8D]
But still - it's a bit duff on the steel plate disc valve issue.
The thickness of the discs [?]
Has it to do actually with the weight of these discs, then this way adjusting the disc valve action [?]
Anders, you can find a description how damper works on www.monroe.com, there are also some pictures there. Things are similar, except that on conventional twin-tube damper valve assembly is divided into two parts - one on the piston (for extraction) and one on the damper inner tube base (for compression), while on the citroen system whole assembly is on the sphere.
You can also download the document Presentation_C5.pdf, found on the download section of Yahoo C5 forum - there is a good picture of C5 sphere and it's valve assembly.
Anyway, there are 4 bores, open on outer side of the sphere (you can see 4 slots under the outer discs), and covered with discs on inner side (for compression), and 4 bores, open on inner side of the sphere, and covered with discs on outer side (for extraction). And, of course, there is a central bore, which is always open. If you bend the outer discs with a screwdriver, you will see the main bores.
On low-speed piston movements, pressure difference between each side of damper valve assembly is low, so main bores remain closed, and central bore controls fluid flow. On medium-speed piston movements, the pressure difference is big enough to bend the discs and uncover corresponding group of 4 much bigger main bores. If discs are thinner, they will bend more, and the damping force at the same piston speed will be lower. On high-speed piston movements, fluid flow is controlled also by the diameter of main bores.
I wouldn't recommend tampering with this assembly, like that Japanese, unless you really know what you are doing, because you can hardly get better results than the factory. Of course, experimenting with different spheres is possible, but as you see, things are more complex than they seem to be at first.
Of course, mechanics don't have a clue about this.
You can also download the document Presentation_C5.pdf, found on the download section of Yahoo C5 forum - there is a good picture of C5 sphere and it's valve assembly.
Anyway, there are 4 bores, open on outer side of the sphere (you can see 4 slots under the outer discs), and covered with discs on inner side (for compression), and 4 bores, open on inner side of the sphere, and covered with discs on outer side (for extraction). And, of course, there is a central bore, which is always open. If you bend the outer discs with a screwdriver, you will see the main bores.
On low-speed piston movements, pressure difference between each side of damper valve assembly is low, so main bores remain closed, and central bore controls fluid flow. On medium-speed piston movements, the pressure difference is big enough to bend the discs and uncover corresponding group of 4 much bigger main bores. If discs are thinner, they will bend more, and the damping force at the same piston speed will be lower. On high-speed piston movements, fluid flow is controlled also by the diameter of main bores.
I wouldn't recommend tampering with this assembly, like that Japanese, unless you really know what you are doing, because you can hardly get better results than the factory. Of course, experimenting with different spheres is possible, but as you see, things are more complex than they seem to be at first.
Of course, mechanics don't have a clue about this.
Alex -
Tx a billion - sharing your knowledge [^]
It is a fact, that the Citroen sphere is the main cause of many mysterios assumptions, especially on the sphere damper valve's function.
With your kind & patient explanations, I'm at least beginning to have a clue on this issue [:o)]
[8D] Tx mate [8D]
Tx a billion - sharing your knowledge [^]
It is a fact, that the Citroen sphere is the main cause of many mysterios assumptions, especially on the sphere damper valve's function.
With your kind & patient explanations, I'm at least beginning to have a clue on this issue [:o)]
[8D] Tx mate [8D]
Anybody interested in this discussion, I found a nice movie from Citroen, describing how the system works on GS/CX, including this damper valve assembly. Here's the link:
http://www.citroen.ac/videos/hydro-gross.rm
Movie size is 48 M.
http://www.citroen.ac/videos/hydro-gross.rm
Movie size is 48 M.
There's a general rule of thumb with all hydraulic Citroëns; the correct ride high is nearly exactly half way between min height and max height. So if you are concerned about your ride height, just measure the height of a wheel arch edge at lowest height then again at max height, calculate the difference and check that that's what you're getting at normal ride height. This may not give you the exact ride height, but it's close enough to show if it's way off or not.
//NiSk
//NiSk