DrTim,
I suddenly now remember that David Hallworth, who writes in this forum, has recently had a problem of his Hydractive being permanently energised in the soft position, and he has resolved it, but I can't remember what the fault was. If you pm him I'm sure he'll hapilly tell you.
regards
George
Full Version Interesting Experience With Spheres
There's a note in Citroenian this month about a Activa flattening it's battery due to soft mode being enabled even when parked up. It turned out to be the hatch switch that was faulty and so the ecu kept energising the electrovalves.
It's seems funny how differently the XM drives compared to my Xantia Exclusive, the XM isn't really floaty at all but does somehow iron out the worst of the bumps in a way the Xantia does not. The main difference seems to be the XM is on steel wheels and the Xantia on alloys with low profiles. Will post tyre size at some stage.
Steve.
It's seems funny how differently the XM drives compared to my Xantia Exclusive, the XM isn't really floaty at all but does somehow iron out the worst of the bumps in a way the Xantia does not. The main difference seems to be the XM is on steel wheels and the Xantia on alloys with low profiles. Will post tyre size at some stage.
Steve.
....update:
yesterday my suspension worked again like it should. Gone is the seeming inability of the wheels to move when meeting smaller road irregularities, producing a crashy feeling and transmitting shacky vibrations to the car's body. It is almost like that faraway day of March 2006, when for one day I discovered what "Citroen magic carpet" means.
The unfortunate detail is that *I* haven't done anything to produce this result!
After a sleepless night of thinking (this issue is genuinelly driving me mad) I can only observe the following:
0/ all wheels changed behavior, not only front or rear. Car rides beautifully now. The interior's plastic trim is not shacking at every little sharp bump/broken tarmac surface.
1/ it is not a difference in the electrics. All voltages and the radio sound of evalves where the same as recorded many other times in past.
2/ regulator cycling time is absolutely identical as measured many other times, between 13-14secs. This would mean that it was not a matter of some internal leak "healing" itself perhaps by debris, and then hydractive valves being opened better/more.
3/ only difference I can observe was the hot day yesterday. It was the first time this year I needed to use the aircon on the motorway because the interior would bake you.
As now I have the front supply of high pressure to hte evalve directly connected from after the pressure regulator, and through a one-way valve, it is not possible that there would be any change of pressure at the front hydractive system at least.
The only senario left is that my struts (all) were binding and yesterday they didn't. The only clue I have is the hot weather, although I don't want to say it's that. Perhaps LHM becomes thinner but I can't think of an effect of that, except perhaps it has lubricated the struts better (like people used to do with BXs). But then LHM would become hot in winter also, some time after running the car, as the LHM tank probably gets hot because of the engine. So I can only think something happens to the struts. I'll start measuring LHM temperature as of today to relate it to behavior. I know from past experiences that today I could perfectly find the car not-so-soft again. BTW, Steve "steel-city" had the oppostie theory afair, ie.e that his car was better with colder weather because LHM becomes thicker and existing leaking minimises so hydractive valves are better pressed open.
Guys, this must be one of the greatest mysteries of the world. I mean, seriously, how many people on the planent know the answer to this problem (that many people experience, as I read in other forums). Some Citroen engineers perhaps?
regards
George
.... 
yesterday my suspension worked again like it should. Gone is the seeming inability of the wheels to move when meeting smaller road irregularities, producing a crashy feeling and transmitting shacky vibrations to the car's body. It is almost like that faraway day of March 2006, when for one day I discovered what "Citroen magic carpet" means.
The unfortunate detail is that *I* haven't done anything to produce this result!
After a sleepless night of thinking (this issue is genuinelly driving me mad) I can only observe the following:
0/ all wheels changed behavior, not only front or rear. Car rides beautifully now. The interior's plastic trim is not shacking at every little sharp bump/broken tarmac surface.
1/ it is not a difference in the electrics. All voltages and the radio sound of evalves where the same as recorded many other times in past.
2/ regulator cycling time is absolutely identical as measured many other times, between 13-14secs. This would mean that it was not a matter of some internal leak "healing" itself perhaps by debris, and then hydractive valves being opened better/more.
3/ only difference I can observe was the hot day yesterday. It was the first time this year I needed to use the aircon on the motorway because the interior would bake you.
As now I have the front supply of high pressure to hte evalve directly connected from after the pressure regulator, and through a one-way valve, it is not possible that there would be any change of pressure at the front hydractive system at least.
The only senario left is that my struts (all) were binding and yesterday they didn't. The only clue I have is the hot weather, although I don't want to say it's that. Perhaps LHM becomes thinner but I can't think of an effect of that, except perhaps it has lubricated the struts better (like people used to do with BXs). But then LHM would become hot in winter also, some time after running the car, as the LHM tank probably gets hot because of the engine. So I can only think something happens to the struts. I'll start measuring LHM temperature as of today to relate it to behavior. I know from past experiences that today I could perfectly find the car not-so-soft again. BTW, Steve "steel-city" had the oppostie theory afair, ie.e that his car was better with colder weather because LHM becomes thicker and existing leaking minimises so hydractive valves are better pressed open.
Guys, this must be one of the greatest mysteries of the world. I mean, seriously, how many people on the planent know the answer to this problem (that many people experience, as I read in other forums). Some Citroen engineers perhaps?
regards
George
....
ps. forgot, also the rear drops at exactly the same rate after switching off (couple of hours to bottom out), so again no indication of a healed leak there (and on brake doseur consequently)...
G
G
...yes...it has not lasted. Today car is again as before. LHM temperature taken this afternoon after a 4 mile run was 43 celcius. Anyway, I've now bought a new rear cylinder and will fit it together with new bearing on the same side but not the other side, so will be able to compare and say whether cylinders' wear play a role in this.
G
G
I find exactly the same - if the ambient temp is over about 25 degrees I get the ride I should. Lower than that and it crashes on small bumps, does not have the floaty ride it should etc.
I do notice that it goes down a bit overnight (it is an anti sink system) but not enough that I am too worried about leakage. Spheres were all new or recharged a year or so ago and made a difference, but did not fix it. Electrovalves seem to be working (radio tests, listening when stopped) and I have done the diode fix to rule that out. However, I think my back one may be sticky judging by the different timings of the jerk at the back on startup when it finally engages.
I am planning a hydraflush at some point (ordered some yesterday) to see if it makes any difference, but don't know when I will get round to putting it in.
I do notice that it goes down a bit overnight (it is an anti sink system) but not enough that I am too worried about leakage. Spheres were all new or recharged a year or so ago and made a difference, but did not fix it. Electrovalves seem to be working (radio tests, listening when stopped) and I have done the diode fix to rule that out. However, I think my back one may be sticky judging by the different timings of the jerk at the back on startup when it finally engages.
I am planning a hydraflush at some point (ordered some yesterday) to see if it makes any difference, but don't know when I will get round to putting it in.
I still personally think that roughness over small irregularities is down to tyres. With a higher ambient temperature, although the pressures will be a little higher, the compound will be softer. I have dropped my tyre pressures from 33 to 30 psi and it makes a noticable difference to the low speed ride, my other XM which is used by my son is still at 33 psi and I can feel the difference immediatly.
Peter.N.
Peter.N.
| QUOTE (Peter.N. @ Jun 1 2007, 10:17 AM) |
| I still personally think that roughness over small irregularities is down to tyres. |
I completely agree.
Our Hydractive susp is superb at handling low frequency road imperfections but the damper rates (sphere orifices) don't like sharp road surface changes - that's where the flexing of the tyrewalls comes into play. I've noticed a greater harshness over potholes since fitting my alloys so have dropped the pressures by a few psi too and live with it for the surefootedness the wider tyres gives the car.
Hi All
From my former work experience I know that personal perceptions of ride performance are very subjective even from different people in the same vehicle let alone different people in different cars running at different speeds/accelerations over different road surfaces. The XM suspension is not intelligent in the sense that it cannot predict the road surface shape that the car is about to ride over. It therefore has to be set up as a comprise to then make the best of the long and short pitch undulations it could be asked to traverse. There is then a question as to whether each individual model of XM is designed to achieve the same ride performance. I suspect not as in my experience even when in good order V6 cars have a slightly better ride than 2.5TD estates. Maybe there is a general car/estate devide in ride performance. Certainly I recently spent a few hours with another club member driving our cars round the same little circuit to compare our perceptions of ride differences. We even tried swapping suspension ECU's. A known good V6 car suspension ECU was put in his 2.0 TCT estate and gave a ride round the circuit that he considered slightly better than the original ECU while I thought they gave the same ride. What was interesting was that I was satisfied that the V6 ECU gave a slightly smoother and more floaty ride in a V6 car. The "foreign" ECU was left in the TCT to try it for a while over known roads and London's local road speed bumps. I await the results with interest. We did conclude that tyre type makes very little difference to ride performance. My experience is that 4 or 5 lbs over pressure can totally remove the ability of a V6 car to appear to float over pot holes. It was how I found out that one of my key ring tyre pressure gauges had a reading error.
Regards
XMexc
From my former work experience I know that personal perceptions of ride performance are very subjective even from different people in the same vehicle let alone different people in different cars running at different speeds/accelerations over different road surfaces. The XM suspension is not intelligent in the sense that it cannot predict the road surface shape that the car is about to ride over. It therefore has to be set up as a comprise to then make the best of the long and short pitch undulations it could be asked to traverse. There is then a question as to whether each individual model of XM is designed to achieve the same ride performance. I suspect not as in my experience even when in good order V6 cars have a slightly better ride than 2.5TD estates. Maybe there is a general car/estate devide in ride performance. Certainly I recently spent a few hours with another club member driving our cars round the same little circuit to compare our perceptions of ride differences. We even tried swapping suspension ECU's. A known good V6 car suspension ECU was put in his 2.0 TCT estate and gave a ride round the circuit that he considered slightly better than the original ECU while I thought they gave the same ride. What was interesting was that I was satisfied that the V6 ECU gave a slightly smoother and more floaty ride in a V6 car. The "foreign" ECU was left in the TCT to try it for a while over known roads and London's local road speed bumps. I await the results with interest. We did conclude that tyre type makes very little difference to ride performance. My experience is that 4 or 5 lbs over pressure can totally remove the ability of a V6 car to appear to float over pot holes. It was how I found out that one of my key ring tyre pressure gauges had a reading error.
Regards
XMexc
Hi XMexc
I am sure you are right. I think its largely blood sugar related, its amazing how much smoother the car runs after you have been into the motorway services and had something to eat on a long journey! and also if you are on a pleasure trip with plenty of time as opposed to a business one.
Your suspension experiments show great dedication! I have tried everything I can think of and have come to the conclusion that is all down to tyres and state of mind.
Peter.N.
PS. Any luck with unsticking the door trim?
I am sure you are right. I think its largely blood sugar related, its amazing how much smoother the car runs after you have been into the motorway services and had something to eat on a long journey! and also if you are on a pleasure trip with plenty of time as opposed to a business one.
Your suspension experiments show great dedication! I have tried everything I can think of and have come to the conclusion that is all down to tyres and state of mind.
Peter.N.
PS. Any luck with unsticking the door trim?
Hi all,
guys: the difference in my car is very distinct. The crashiness over small irregularities is only *one* symptom of the "bad" state. And you could say that it is down to tyres or other, but I haven't noticed such a dramatic day-to-day change in ride in any other car, on various different tyres, and temperature fluctuations etc. The harsh crashy ride on potholes etc is well documented, many people talk about it, and not only XM owners. The problem is that XMs are a relatively new advent in the second-hand market, while BX owners immediately advise "sticky struts" when somebody complains about it. But from all I've read I'm convinced that when people use the word "crashiness" they all refer to the same problem that I have. Note, I've driven my car:
a/ with flat spheres
b/ with a front sphere busted
c/ with wrong spheres
d/ with the ECU off, i.e. car in hard.
The "crashy" feeling is very distinct!!
What makes me think of sticking struts is the other symptoms: for example, when car is in its "bad", if a wheel falls in a pothole, it makes the car fall in the hole, instead of only the wheel moving and the car's body staying level. The difference is very distinct: it feels like a very strongly damped conventional car, or one with a very stiff antiroll bar. The wheel just doens't move quickly enough -downwards!-On comression, it "crashes". I once owned a Clio that I had fitted with 4cm lowered/harder Eibach springs and red Konis at front. My XM "hunts" holes to exaclty the same degree as the Clio. The difference is that conventional cars don't feel that crashy probably due to more rubber around. While, when like yesterday it gets "good", the XM swallows everything, absolutely everything. And I noticed it was quieter in a cobbled street I drive throught lately. This effect is obviously not tyre-related.
I now know it is not a matter of not-opening hydractive valves, because, as opposed to other stages my car has passed, I have now lots of evidence of softness (ie the middle sphere being in play): when I brake at the traffic lights I can see the front returning from compression when I finally come to rest and leave the brakes -which I did not have in the past-. I can see the car lifting when even 1 person gets out of it, which I couldn't see in the past. It does wallow in long motorway indulations.
The symptoms it gives therefore seem related to the *speed* at which the wheel is asked to move. Precisely, it seems like struts cannot move freely enough to absorb small irregularities. Specially in some situations with broken tarmac, it also gets ridiculously noisy (road noise). Thus there are only two possibilites:
1/ my hydractive valve still misbehaves and cannot keep open under all situations. Despite there's a new evalve and despite I've secured the high pressure suplly to it with a one-way valve (refering to my front system, rear is untouched). This looks unlikely. Only possibity is that the both sides of piping where the LHM flows from corners to middle sphere, are very blocked with dirtiness. But this would't change that much day-to-day. Or the hydractive block's channels are very dirty and blocked inside. The way of the hight pressure line that opens up the hydractive valve cannot be blocked because the evalse have a filter on them so nothing passes past..
2/ the struts are sticky and add a damping factor to the suspension....This is the last possibilty as I've literally fixed everyhting else. Sticky struts in XMs are not documented afaik. Now, why did this improve the other day, I don't know, but it is interesting that rowanmoor seems to report exaclty the same problem AND change as mine.
Recently I was getting convinced that "the XM is like this, it's not like a CX" and was prepared to fit comfort spheres. Althoug I coulnd't really believe it. But yesterdays experience reminded me that the XM is excellent when it functions as designed.
So, new cylinder soon, and it all will show.
regards
George
guys: the difference in my car is very distinct. The crashiness over small irregularities is only *one* symptom of the "bad" state. And you could say that it is down to tyres or other, but I haven't noticed such a dramatic day-to-day change in ride in any other car, on various different tyres, and temperature fluctuations etc. The harsh crashy ride on potholes etc is well documented, many people talk about it, and not only XM owners. The problem is that XMs are a relatively new advent in the second-hand market, while BX owners immediately advise "sticky struts" when somebody complains about it. But from all I've read I'm convinced that when people use the word "crashiness" they all refer to the same problem that I have. Note, I've driven my car:
a/ with flat spheres
b/ with a front sphere busted
c/ with wrong spheres
d/ with the ECU off, i.e. car in hard.
The "crashy" feeling is very distinct!!
What makes me think of sticking struts is the other symptoms: for example, when car is in its "bad", if a wheel falls in a pothole, it makes the car fall in the hole, instead of only the wheel moving and the car's body staying level. The difference is very distinct: it feels like a very strongly damped conventional car, or one with a very stiff antiroll bar. The wheel just doens't move quickly enough -downwards!-On comression, it "crashes". I once owned a Clio that I had fitted with 4cm lowered/harder Eibach springs and red Konis at front. My XM "hunts" holes to exaclty the same degree as the Clio. The difference is that conventional cars don't feel that crashy probably due to more rubber around. While, when like yesterday it gets "good", the XM swallows everything, absolutely everything. And I noticed it was quieter in a cobbled street I drive throught lately. This effect is obviously not tyre-related.
I now know it is not a matter of not-opening hydractive valves, because, as opposed to other stages my car has passed, I have now lots of evidence of softness (ie the middle sphere being in play): when I brake at the traffic lights I can see the front returning from compression when I finally come to rest and leave the brakes -which I did not have in the past-. I can see the car lifting when even 1 person gets out of it, which I couldn't see in the past. It does wallow in long motorway indulations.
The symptoms it gives therefore seem related to the *speed* at which the wheel is asked to move. Precisely, it seems like struts cannot move freely enough to absorb small irregularities. Specially in some situations with broken tarmac, it also gets ridiculously noisy (road noise). Thus there are only two possibilites:
1/ my hydractive valve still misbehaves and cannot keep open under all situations. Despite there's a new evalve and despite I've secured the high pressure suplly to it with a one-way valve (refering to my front system, rear is untouched). This looks unlikely. Only possibity is that the both sides of piping where the LHM flows from corners to middle sphere, are very blocked with dirtiness. But this would't change that much day-to-day. Or the hydractive block's channels are very dirty and blocked inside. The way of the hight pressure line that opens up the hydractive valve cannot be blocked because the evalse have a filter on them so nothing passes past..
2/ the struts are sticky and add a damping factor to the suspension....This is the last possibilty as I've literally fixed everyhting else. Sticky struts in XMs are not documented afaik. Now, why did this improve the other day, I don't know, but it is interesting that rowanmoor seems to report exaclty the same problem AND change as mine.
Recently I was getting convinced that "the XM is like this, it's not like a CX" and was prepared to fit comfort spheres. Althoug I coulnd't really believe it. But yesterdays experience reminded me that the XM is excellent when it functions as designed.
So, new cylinder soon, and it all will show.
regards
George
Hi Peter
Have had another couple of goes at removing the door trim from the trial door. Not got it off yet but neither have I broken it. I have made up the pair of front washer blanks ready for you.
Regards
XMexc
Have had another couple of goes at removing the door trim from the trial door. Not got it off yet but neither have I broken it. I have made up the pair of front washer blanks ready for you.
Regards
XMexc
| QUOTE (rowanmoor @ Jun 1 2007, 08:34 AM) |
| I find exactly the same - if the ambient temp is over about 25 degrees I get the ride I should. Lower than that and it crashes on small bumps, does not have the floaty ride it should etc. I do notice that it goes down a bit overnight (it is an anti sink system) but not enough that I am too worried about leakage. Spheres were all new or recharged a year or so ago and made a difference, but did not fix it. Electrovalves seem to be working (radio tests, listening when stopped) and I have done the diode fix to rule that out. However, I think my back one may be sticky judging by the different timings of the jerk at the back on startup when it finally engages. I am planning a hydraflush at some point (ordered some yesterday) to see if it makes any difference, but don't know when I will get round to putting it in. |
Hi rowanmoor
my car is on correct spheres with satisfactory pressures -checked at about 10% lower than new-. It still does it. It even did it when I had spheres with orifices the size of a CX: wallowing alot and much of a magic carpet, but still the same crashy story in sharper items. I specially remember the "bang" it was doing when a wheel met the exiting edge of a pothole (ie wheel required to go up).
I was worried of the importance of leaks till recently, but I'm more and more convinced it's not related. It's the wheels that can't move properly when asked to follow irregularities of even no more than 1cm of height fluctuation. It feels like the suspension has "frozen". This shouldn't relate to any leaking anywhere, or spheres, when at the same time the car can swallow effectively humps 10cm tall.
George
Hi george
I have 'comfort' spheres on mine, but it doesn't help a lot with the 'crashiness' you describe, just makes the car wallow a bit like the CX - which also 'crashed' over bumps. My son doesn't like them (the comfort spheres) says they make his wife feel sick - I like them though.
If you do find a mechanical reason for this phenomina, I would be very pleased to know about it.
XMexc - Thanks, I will give a ring or an email.
Peter.N.
I have 'comfort' spheres on mine, but it doesn't help a lot with the 'crashiness' you describe, just makes the car wallow a bit like the CX - which also 'crashed' over bumps. My son doesn't like them (the comfort spheres) says they make his wife feel sick - I like them though.
If you do find a mechanical reason for this phenomina, I would be very pleased to know about it.
XMexc - Thanks, I will give a ring or an email.
Peter.N.
Hi George
I am trying to get my head round crashiness, potholes and sticking struts. When one front wheel is presented with a pothole and that strut is sticking it should logically become unloaded and skate over the hole. The car is a large mass moving forward with considerable momentum and will not easily change direction. The front wheel/suspension is a much smaller mass therefore held close to the cars forward motion by the sticking strut. Only if the diagonally opposite rear strut over compensates will the wheel be pushed into the hole with the weight of the car behind it and it would take that weight to generate the crashiness sensation as the wheel hits the far side of the hole. Perhaps sticking struts behave like bump stops and all the force is taken by the rubber in the strut top. Now rubber suspensions I know a bit about and they can lock solid at critical frequencies with quite destructive results. I will give it a bit more thought.
Regards
XMexc
I am trying to get my head round crashiness, potholes and sticking struts. When one front wheel is presented with a pothole and that strut is sticking it should logically become unloaded and skate over the hole. The car is a large mass moving forward with considerable momentum and will not easily change direction. The front wheel/suspension is a much smaller mass therefore held close to the cars forward motion by the sticking strut. Only if the diagonally opposite rear strut over compensates will the wheel be pushed into the hole with the weight of the car behind it and it would take that weight to generate the crashiness sensation as the wheel hits the far side of the hole. Perhaps sticking struts behave like bump stops and all the force is taken by the rubber in the strut top. Now rubber suspensions I know a bit about and they can lock solid at critical frequencies with quite destructive results. I will give it a bit more thought.
Regards
XMexc
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