I've just noticed that the C6 has two hydractive spheres per axle. There must be a maximum size of sphere that can be manufactured and installed, so maybe this is Citroen's solution to providing maximum volume for maximum ride comfort at an economic price?
Macaroni, if I were looking for max comfort on a Xzantia I think I would first follow the advice in this thread to ensure freedom of movement of all the friction-bearing components. Once that was done I would think about fitting the largest available spheres (seems to be 500cc) with the same pressure and damper sizes that are standard for your car.
If you are only unhappy with the front end that should cost you less than £60 from, for example, GSF including delivery.
Please let us know how you get on. For me, I'm now thinking of following my own advice and fitting 500cc spheres to the front legs on my XM!
Regards,
Derek
A request by proxy, softest possible Xantia?
Moderator: RichardW
-
FrenchLeave
- Posts: 359
- Joined: 18 Jan 2005, 21:47
- Location: 5 miles N. of Boston, Lincs
- My Cars:
-
FrenchLeave
- Posts: 359
- Joined: 18 Jan 2005, 21:47
- Location: 5 miles N. of Boston, Lincs
- My Cars:
As a final throw I thought I would try to explain my thinking with regard to increased sphere volume.
Probably the best way to do this is to use example numbers for our calculations. So taking two spheres, one of 400cc volume and the other of 500cc; both at the same starting pressure of 50 bar (750 psi).
With a supported weight of 1000 lbs (none of this SI rubbish here but I will convert it if anyone insists!) and piston area of 1 square inch, the supporting pessure will be 1000 psi and the compressed volumes will be .75 x 400cc = 300cc and 0.75 x 500cc = 375cc respectively.
Assume the car hits a bump and the bump force = 2000 lbs. From pressure times volume is a constant we find that the smaller sphere compresses to 0.5 x 300 = 150cc and the larger sphere to 0.5 x 375cc = 187.5cc. So the 400 cc sphere has a volume change (and this is the important part) of 300 - 150 = 150cc and the 500cc sphere changes to 375 - 187.5 = 187.5.
If we divide the volume change by the piston area we get the vertical wheel movement, so the larger sphere allows 25% more wheel movement over any given bump than the smaller sphere. Carry out the calculation for any bump load and you come up with the same result, 25% more wheel movement for the larger sphere. That means softer suspension.
So there you are. For comfort fit the largest spheres you can but with two provisos; as Simon said you shouldn't muck about with damper settings and it's sensible to stick with the standard inflation pressure. If you have some time to spare you could feed the formulae into a spreadsheet and try the effects of changing the inflation pressure. You could even plot out the results using the graphing function.
Regards,
Derek
Probably the best way to do this is to use example numbers for our calculations. So taking two spheres, one of 400cc volume and the other of 500cc; both at the same starting pressure of 50 bar (750 psi).
With a supported weight of 1000 lbs (none of this SI rubbish here but I will convert it if anyone insists!) and piston area of 1 square inch, the supporting pessure will be 1000 psi and the compressed volumes will be .75 x 400cc = 300cc and 0.75 x 500cc = 375cc respectively.
Assume the car hits a bump and the bump force = 2000 lbs. From pressure times volume is a constant we find that the smaller sphere compresses to 0.5 x 300 = 150cc and the larger sphere to 0.5 x 375cc = 187.5cc. So the 400 cc sphere has a volume change (and this is the important part) of 300 - 150 = 150cc and the 500cc sphere changes to 375 - 187.5 = 187.5.
If we divide the volume change by the piston area we get the vertical wheel movement, so the larger sphere allows 25% more wheel movement over any given bump than the smaller sphere. Carry out the calculation for any bump load and you come up with the same result, 25% more wheel movement for the larger sphere. That means softer suspension.
So there you are. For comfort fit the largest spheres you can but with two provisos; as Simon said you shouldn't muck about with damper settings and it's sensible to stick with the standard inflation pressure. If you have some time to spare you could feed the formulae into a spreadsheet and try the effects of changing the inflation pressure. You could even plot out the results using the graphing function.
Regards,
Derek
-
Stempy
- Posts: 1626
- Joined: 26 Feb 2004, 23:21
- Location: Cloud Cuckooland
- My Cars: C5 V6 Mk1 assainated by wife
Renault Kangoo 1.6 auto, tarted up and remapped
Still missing the Xantia V6
Not missing the AX - Contact:
The way I see it, sphere volume is roughly equivalent to spring length in a normal shock and determines total suspension travel (or deflection), sphere pressure is comparable to spring rate (or stiffness) and determines the amount of movement under any given force and damping is damping whichever way you look at it and controls the speed of movement of the suspension under any given force.
It infuriates me to be wrong when I know I'm right
Lexia ponce
http://perception.dyndns.biz/~avengineering/index.htm
Lexia ponce
http://perception.dyndns.biz/~avengineering/index.htm
Actually I didnt say don't muck about with the damper settings 
But I was warning about the potential dangers of using a sphere that is radically different than what the car was designed for. If you head in the direction of higher pressure and larger damping hole you can easily end up with a car with boat-like unsafe handling.
In extreme cases the diaphram in the sphere might even bottom during suspension travel.
CX front spheres were a good example because they're a lot different in pressure, damping, and size than most of the newer models. (I don't think any other spheres have a damper hole as large as 1.9mm for example)
Something else to consider is that the damper hole is only half the equation for damping - also critical is the threshold valve itself - basically just a bunch of spring steel washers riveted to a small block which block all of the through ports except for the small bypass hole.
The number and thickness of these washers set the threshold above which they will bend and allow largers flows of oil through. Below this threshold the oil can only flow through the small bypass hole.
These threshold valves vary in strength from model to model, and also between front and rear spheres, and there is no easy way of determining their characteristics by looking at them. (They all look much the same, and you can only see the washers on the outside, not the inside ones)
This is the main reason to avoid mixing spheres between non-similar models.
In most models I would say that you won't gain much by increasing damper holes because they're already optimally tuned. Most of the Citroens I've driven I've found the damping was either spot on (critically damped) or a little bit underdamped and floaty already.
The only models that probably have quite firm damping that could be eased off a bit would be ones like the BX16v and CX Turbo, both of which have damping that is deliberately a lot firmer than usual.
When I see people wanting to drill the damping holes out to get a better ride my first thoughts are always "what else is wrong with the suspension" and you can bet there are other issues like rear arm bearings, worn front struts, worn balljoints, bushes etc which are contributing to a poor ride, rather than the specific springing/damping tuning that Citroen chose for that model...
The other problem is a pschological problem - Citroen's ride so well most of the time that you get used to the lack of bumpiness and every tiny bump that you DO feel becomes 10x more obvious. (You start expecting near perfection in ride on any surface...)
Everyone who drives a Citroen needs to drive another conventionally sprung car at least once a week to remind them of the difference...
I've had a few problems with ride in my Xantia in the past (almost sorted now) and even then I still get overly critical about its ride and its a rude awakening when I hop in another car (I seldom drive other cars) and go back to the Xantia and gain new appreciation for just how good it's ride actually is...
Regards,
Simon
But I was warning about the potential dangers of using a sphere that is radically different than what the car was designed for. If you head in the direction of higher pressure and larger damping hole you can easily end up with a car with boat-like unsafe handling.In extreme cases the diaphram in the sphere might even bottom during suspension travel.
CX front spheres were a good example because they're a lot different in pressure, damping, and size than most of the newer models. (I don't think any other spheres have a damper hole as large as 1.9mm for example)
Something else to consider is that the damper hole is only half the equation for damping - also critical is the threshold valve itself - basically just a bunch of spring steel washers riveted to a small block which block all of the through ports except for the small bypass hole.
The number and thickness of these washers set the threshold above which they will bend and allow largers flows of oil through. Below this threshold the oil can only flow through the small bypass hole.
These threshold valves vary in strength from model to model, and also between front and rear spheres, and there is no easy way of determining their characteristics by looking at them. (They all look much the same, and you can only see the washers on the outside, not the inside ones)
This is the main reason to avoid mixing spheres between non-similar models.
In most models I would say that you won't gain much by increasing damper holes because they're already optimally tuned. Most of the Citroens I've driven I've found the damping was either spot on (critically damped) or a little bit underdamped and floaty already.
The only models that probably have quite firm damping that could be eased off a bit would be ones like the BX16v and CX Turbo, both of which have damping that is deliberately a lot firmer than usual.
When I see people wanting to drill the damping holes out to get a better ride my first thoughts are always "what else is wrong with the suspension" and you can bet there are other issues like rear arm bearings, worn front struts, worn balljoints, bushes etc which are contributing to a poor ride, rather than the specific springing/damping tuning that Citroen chose for that model...
The other problem is a pschological problem - Citroen's ride so well most of the time that you get used to the lack of bumpiness and every tiny bump that you DO feel becomes 10x more obvious. (You start expecting near perfection in ride on any surface...)
Everyone who drives a Citroen needs to drive another conventionally sprung car at least once a week to remind them of the difference...
I've had a few problems with ride in my Xantia in the past (almost sorted now) and even then I still get overly critical about its ride and its a rude awakening when I hop in another car (I seldom drive other cars) and go back to the Xantia and gain new appreciation for just how good it's ride actually is...
Regards,
Simon
Simon
1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White
2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
1997 Xantia S1 2.0i Auto VSX
1998 Xantia S2 3.0 V6 Auto Exclusive
1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White
2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
1997 Xantia S1 2.0i Auto VSX
1998 Xantia S2 3.0 V6 Auto Exclusive
This info isn't for me, but someone I know who can't seem to join the forum.
He has replied to your answers below....
Sincere thanks to everyone who responded to my query - you've told me all I wanted to know, and more! My conclusion is that my Xantia is probably not riding as well as it should, and that I should start by finding out why it takes a while to come up to height. Although the four "corner" spheres are new, there may be one elsewhere that isn't, and that one can evidently affect the ride. Once that's sorted out, different but compatible spheres may bring a further improvement. I'll report back in due course, but this sort of thing can take a while, as I have no mechanical skills.
Two more points of concern, to which I'm sure you'll know the answers:
(1) The heating and ventilation systems on modern cars seem unable to provide "warm feet, cool head". On the 504 there are two central vents permanently connected to the outside air; the volume of air they admit can be controlled (down to zero), as can their angle.
On the 405 there are no such independent vents; the best I can manage is warmer air to feet, cooler air to head - but certainly not cold. The Xantia has climate control, and only two small vents (one each side) are "always cold"; not enough to balance the warm air from the other outlets. Is there a way round this, or do I have to open a window slightly - and put up with traffic noise? This isn't just a matter of comfort - an alert driver is a safer driver.
(2) I have read that with hydropneumatic suspension "the ride becomes harsh at low speeds". Is this true? If so (a) what is considered a low speed; and (b) why does it happen? (In case any doubt remains - my Xantia definitely isn't hydractive).
Thanks again -
LD
He has replied to your answers below....
Sincere thanks to everyone who responded to my query - you've told me all I wanted to know, and more! My conclusion is that my Xantia is probably not riding as well as it should, and that I should start by finding out why it takes a while to come up to height. Although the four "corner" spheres are new, there may be one elsewhere that isn't, and that one can evidently affect the ride. Once that's sorted out, different but compatible spheres may bring a further improvement. I'll report back in due course, but this sort of thing can take a while, as I have no mechanical skills.
Two more points of concern, to which I'm sure you'll know the answers:
(1) The heating and ventilation systems on modern cars seem unable to provide "warm feet, cool head". On the 504 there are two central vents permanently connected to the outside air; the volume of air they admit can be controlled (down to zero), as can their angle.
On the 405 there are no such independent vents; the best I can manage is warmer air to feet, cooler air to head - but certainly not cold. The Xantia has climate control, and only two small vents (one each side) are "always cold"; not enough to balance the warm air from the other outlets. Is there a way round this, or do I have to open a window slightly - and put up with traffic noise? This isn't just a matter of comfort - an alert driver is a safer driver.
(2) I have read that with hydropneumatic suspension "the ride becomes harsh at low speeds". Is this true? If so (a) what is considered a low speed; and (b) why does it happen? (In case any doubt remains - my Xantia definitely isn't hydractive).
Thanks again -
LD