Grey colour spheres, Designed for hydractive III

[Jan-hendrik]

When Citroën designed their Hydractive 3 suspension they re-designed the spheres with new nylon membranes, which greatly slow the rate of deflation. These are recognisable by their grey colouring.

Older, green coloured, suspension spheres typically last between 60,000 and 100,000 km

Source: Wikipedia

I wonder about the 60k and 100k km. Perhaps that's true if you drive that distance in a cool climate within 3 to 5 years. At least that's what my experience is.

If you have read this thread:
http://club-xm.com/forum/index.php?showtopic=5088&st=0
you noticed that my new SC/MAC sphere is grey. Must be one of the latest generation with unlimited life expectancy! That is very reassuring. The unit price was only 6,525 yen, while the standard green coloured regulator sphere was priced at more than double that at 14,700 yen. I can't begin to imagine why this gap.

Does anyone have experience with fitting these grey C5 spheres on the XM?
Are they available to replace all spheres on the XM?

Oh, yes, the part number for the new SC/MAC sphere is 529304, so the same number as for the green one.

[robertmnorton]

Hi Jan,no personal experience but cit have a document detailing the changeover to grey coloured spheres for xm/xantia.I've never seen one so don't know if they are the same low profile spheres used on c5/c6.Both c5/c6 use a synthetic hydraulic oil,so presumeably the diaphragm material in the low profile spheres was changed to suit.They may well be compatable with LHM.
robertm

Found it.

This post has been edited by robertmnorton on July 03, 2011 09:30 pm

[kenhall1202]

When Citroen were developing the new saucer 'sphere' design, first seen on the C5, the XM in later years was used as a 'guinea pig' for testing the new diaphragm material. These spheres used on XMs can usually be found only on the two front struts and the front centre hydractive position and are easily identified by having three prominent dimples stamped around the filler screw. My 1996 2.1TD had them and I can confirm from my own pressure measurements that they lose pressure extremely slowly.

Earlier spheres used two types of polyurethane based diaphragm material known as 'Urepan' and 'Desmopan'. These diaphragms are slightly permeable to nitrogen resuting in the slow loss of pressure during use on the car which we are all familiar with.

The new diaphragm material is of multilayer construction ('multicouche') with a much lower or possibly negligible nitrogen permeability. This together with the saucer design results in much less flexing and stressing of the diaphragm in use. These two new design features meant that Citroen were able to make the spheres as 'long life'(?) totally sealed units, ie there is no filler screw ( although an aftermarket refilling facility (Valprex?) is available which entails drilling and tapping the sphere to allow a filling valve to be added).

Citroen's move to the current identifying grey finish for both saucer and replacement 'conventional' spheres presumably means that they all have the new multilayer diaphragm material which seems to indicate that it is compatible with both LHM and LDS hydraulic fluids.

I have heard of people fitting saucer spheres to replace the older type ( eg as a long life main accumulator), but having to use a neck spacer in order to get them fitted into the limited space available.

Ken

[Jan-hendrik]

I posted this on XM-L in May in response to a query:

Both desmopan and urepan are polyurethane resins.
Citroen offers a choice in some cases. Urepan being of a newer generation and
sturdier material, so probably a better choice as it will last longer.

Urepan is the material of choice in my area.

I have been aware of the existence of the multicouche spheres which are fitted to the front of my XM as well.
I just wonder if they have the same material membranes as the grey sphere which was just fitted to replace the SC/MAC sphere. Wikipedia talks about nylon