Fitting BX speres to the xantia front end.

citronut · Post by **citronut** » 09 Jul 2009, 08:08

Nigel wrote
"well we can't all be pro mechanics"

Nigel i thought we had got passed your misinterpreting of my use of the english language,

i do/did not mean any bitchyness from my coments what so ever,

i just could not think and still cant what linkage/s you talk about, and that is all i ment,

please dont take offence as this forum is usualy quite plesant,
unlike the OFFENCIVE bx forum

kind regards
malcolm

Sid_the_Squid · Post by **Sid_the_Squid** » 09 Jul 2009, 09:45

You can then compare the volume/pressure/damping and choose a sphere that will suit.

Forgive my ignorance, but which of the factors listed (volume/pressure/damping) equates to a softer ride?

My first thought would be pressure, higher=softer, but that cant be rigth as the bx ones are lower than the xantia spheres, could someone enlighten me please.

addo · Post by **addo** » 09 Jul 2009, 10:42

A lower pressure gives softer riding.

It's hard to super-simplify, but basically the preassure of the gas, always equals the fluid pressure on the other side of your sphere's diaphragm. When the car is still, pressure on each side is comparatively low.

When the suspension is compressed for any wheel, the fluid in that strut is forced into a smaller available space, and this presses the sphere membrane into the gas side more. When the available "room" for the gas is reduced, its pressure goes up. After a point, the gas pressure will equal the fluid being forced against it, and suspension travel will start to rebound.

With a lower sphere pressure, it allows more fluid ingress to the sphere before starting to rebound. This means more suspension travel, and a "softer" ride.

Stempy · Post by **Stempy** » 09 Jul 2009, 11:25

The greatest influence will be from the diameter of the damping hole. A larger hole will mean less damping and hence a softer ride and more comfort but handling stability will be reduced. Conversely, a smaller hole will increase the damping and give a firmer but less comfortable ride but more controlled handling.

The HA system is supposed to give you the best of both worlds by switching in the extra sphere for comfort and switching it out for cornering stability..

The volume and pressure equate to spring length and spring rate on normal suspension.

Sid_the_Squid · Post by **Sid_the_Squid** » 09 Jul 2009, 13:46

Thanks guys, regards pressure, I'm a bit confused, if lower pressure = softer ride, why when a sphere is going flat does the ride not get softer?

red_dwarfers · Post by **red_dwarfers** » 09 Jul 2009, 16:11

Sid_the_Squid wrote:Thanks guys, regards pressure, I'm a bit confused, if lower pressure = softer ride, why when a sphere is going flat does the ride not get softer?

I was just going to ask that!

citronut · Post by **citronut** » 09 Jul 2009, 16:22

try this link
http://oto.to/schematy/citroen_kule.pdf

it dose show higher presure in fronts than rear

regards malcolm

Xaccers · Post by **Xaccers** » 09 Jul 2009, 16:39

Sid_the_Squid wrote:Thanks guys, regards pressure, I'm a bit confused, if lower pressure = softer ride, why when a sphere is going flat does the ride not get softer?

The dampner holes dictate the softeness by controlling how quickly fluid can enter/exit the sphere.
With small holes, the compressing strut hits a resistance from the dampners and so the strut has to absorb more of the energy giving a harder ride.
With large holes, the strut has less resistance to compression and the sphere absorbs more of the energy.
The gas in the sphere acts like springs, the higher the pressure/volume, the longer the equivalent spring.
So a flat sphere is like a car with short springs, they can't compress very far before they hit the stops.
The higher the pressure in the sphere, the more it can resist being totally compressed, so under compression it can absorb more energy.

I would guess that the dampners in BX spheres are larger than in non-HA Xantias and so give it a softer ride, yet not too soft to be uncontrolable.

I would also guess that estate rear spheres have smaller holes than hatchbacks giving a harder ride even though they are of higher pressure.
This would be because of there's more chance of regularly carrying weight in the back of an estate, so the suspension needs to be firmer.
An idea they seem to have extended to the Picasso (with it's girders for suspension) as dad reports his is a lot more comfortable with a load of rubble in the boot!

Stempy · Post by **Stempy** » 09 Jul 2009, 17:18

In fact. estate rear corner spheres have no damping apertures as the damping is taken care of elsewhere. A very good reason not to fit estate rears to a saloon.

Stempy · Post by **Stempy** » 09 Jul 2009, 17:20

Sid_the_Squid wrote:Thanks guys, regards pressure, I'm a bit confused, if lower pressure = softer ride, why when a sphere is going flat does the ride not get softer?

What you have to bear in mind is that as the pressure falls, so does the volume.

red_dwarfers · Post by **red_dwarfers** » 09 Jul 2009, 18:20

Ahh so when there is little pressure in the sphere, the volume of gas decreases until it gets to the point where there is only fluid in the sphere as the diaphragm is pushed up against the top of the sphere.

If the apature is a pin prick, then in the space of say 2 seconds, very little fluid can be transferred in or out of the sphere so the height of the car stays still over the bump creating a shock for the passengers. If the apature was 5cm wide, fluid could freely move in and out letting the pressure of the sphere deal with the damping. Though if this was done, the pressure of the sphere would have to be a good amount higher else every time we went over a bump the diaphragn would be resting near the top of the sphere, making the car look chav-tastic

citrov6 · Post by **citrov6** » 10 Jul 2009, 07:23

Stempy wrote:The greatest influence will be from the diameter of the damping hole. A larger hole will mean less damping and hence a softer ride and more comfort but handling stability will be reduced. Conversely, a smaller hole will increase the damping and give a firmer but less comfortable ride but more controlled handling.

The HA system is supposed to give you the best of both worlds by switching in the extra sphere for comfort and switching it out for cornering stability..

The volume and pressure equate to spring length and spring rate on normal suspension.

so what is cornering like with the bx or xm spheres, i like the idea of comfort, but not too much at the expense of cornering,

does HA take out the slop in cornering even with the bigger spheres , how does this compare to standard xant spheres?

Stempy · Post by **Stempy** » 10 Jul 2009, 07:43

The most notable effect is greater body roll and a bit of wallowing, it kind of depends on how aggressively you corner as to whether this will bother you or not. I only made one journey with the BX spheres so didn't get a chance to assess them fully. XM spheres are very close to the originals but offer better bump absorbtion.

Sid_the_Squid · Post by **Sid_the_Squid** » 10 Jul 2009, 09:23

What you have to bear in mind is that as the pressure falls, so does the volume.

Makes sense, I was pondering this yesterday, and came to the same conclusion.

citrov6 · Post by **citrov6** » 10 Jul 2009, 13:06

thanks, might put xm on see how it drives