Which Spheres, Standard or Comfort

[xm_on_a_shoestring]

GFS sell standard and "comfort" spheres. Which ones do I put on for 2.5td estate. Is it best to get standard and make sure everything else is working as it should? What to comfort spheres actually do?
The rear of my estate has started to "sink" overnight - is this the centre rear sphere that stops it dropping. Or would it be just as wise to replace all three across the rear?
I tow a caravan frequently too.

shoestring

[Peter.N.]

Hi Shoestring

I have comfort spheres on one of mine and it makes the ride a little wallowy. I quite like it but my daughter in law says it makes her feel sick. They have softer damping i.e. the holes are slightly larger. Feels somewhat like a CX.

Sorry, I just read the rest of your post. The centre sphere is the one responsible for the soft ride on the standard suspension setting. Sinking is due generally to wear in the hydraulic system, unless yours has anti sink. Mine sinks, but it comes up as soon as I start so I dont worry about it.

Peter.N.

This post has been edited by Peter.N. on July 07, 2007 04:09 pm

[DerekW]

Hin Shoestring,

As peter says, the spheres don't have any effect on the rate of sinking. Without anti sink, overnight sinking may be acceptable but with it your car should stay up for weeks.

Sinking is always caused by internal leakage; to locate the source, go to the hydraulic tank and disconnect the return lines one by one. For overnight sinking you aren't looking for a massive flow, but you should be able to decide which is the culprit. What's the betting it's one of the rear cylinders?

Derek

[xm_on_a_shoestring]

Hi Derek & Peter N
Thanks for the replies.
I have just come back last night from Penzance Cornwall after a business meeting (nearly 700 miles round trip) and my trusty XM never missed a beat.
On my way home up the M5, I decided to get my cruising speed up from 75-80 to 85-90.
A peculiar thing happened (my better half was with me as well and she also commented), the "magic carpet" ride seemed to return the faster we were travelling!
Is there an explanation to this or were we just both imagining it!?

I shall be getting my rear spheres this week anyway, as we are away to France again this year for school holidays. This time I hope my my car will get further than Dover! It did Cornwall no problems.

shoestring

[Peter.N.]

Hi Shoestring

No, its not imagination, that is a characteristic of hydropnumatic suspension. It copes very well with large undulations but not with small, sharp ones. At high speed the forward inertia prevents it 'dropping' into small holes so you get the full effect of the smooth ride.

Peter.N.

[xm_on_a_shoestring]

Hi Peter N, Derek W
I've collected my spheres from GFS today. I ordered rear centre, two rear suspension and anti sink (4 total).
When I collected them they were short of one rear suspension sphere.
So I've replaced the rear centre and the anti sink. The suspension spheres will have to be done next weekend.
Is the anti sink the one behind the engine?
Is so, the one I removed says accumulator and has a large hole with no valve. The new one is solid centre with an approx. 5 mm drilled downed the centre with no valve, totally different.
Can anyone clarify this?
shoestring

[Peter.N.]

Hi Shoestring

All the centre spheres I have replaced have been like an accuculator sphere whith just a large hole, but having said that, 5mm sounds to large a hole for a suspension sphere, so unless they have modified them, I dont know what you've got!

Peter.N.

[kenhall1202]

Hi shoestring,

The sphere with the solid centre and 5mm threaded hole is the anti-sink sphere which is fitted at the rear nearside (front of) subframe area (at least it is on my '96 2.1TD).
It is attached to a bracket by a big nut on the outside sphere neck thread and a hydraulic pipe connects to the 5mm port with a conventional Citroen connection. I replaced mine several years ago but swore never again because the job was a real pain requiring exhaust removal and partially dropping the subframe just to get enough access to loosen the rusty nut (application of stilsons was required I think!). There is also the worry that the pipe union might round off or shear if it has rusted up!
Sorry to be such a pessimist but all in all I don't think it is worth the hassle changing this sphere especially on high mileage cars where increased piston leakage means that the anti-sink is ineffective anyway.

Regards Ken Hall

[Peter.N.]

Ah! sorry, never had one of those, but I shall know another time.

[DerekW]

Sorry, double posting

This post has been edited by DerekW on July 14, 2007 11:45 pm

[DerekW]

Hi Shoestring,

Slight confusion here. The accumulator sphere is the one low down in front of the engine; the one behind the engine is the front hydractive sphere, easily recognised because it has two large diameter pipes leading to it.

The anti sink sphere has no effect on the anti sink system, its sole purpose in life is to provide an emergency pressure supply to the rear brakes in the event of hydraulic failure. This is necessary because the rear brakes get their supply from the rear suspension and if there is a hydraulic failure the anti sink valve will close, isolating the rear suspension (and the front as well, of course) and thus cutting off the pressure to the rear brakes.

The front brakes get their emergency supply from the accumulator.

Derek

[xm_on_a_shoestring]

I could only see a centre rear sphere (accumulator) on my car (2.5td estate). Does the 2.5td estate actually have an anti sink or not? If so where should I be/not be looking.
shoestring

[DerekW]

According to the workshop manual, antisink was introduced on 1995 cars, so unless your car is a late 1994 ('95 model) it probably doesn't have anti sink.

To give you some more background information, the older system had a hydraulic pump which made all its output available to all systems, with a priority valve giving preference to brakes and steering. As a result, a collapsed suspension would pump up quite quickly in the morning. Then Citroen introduced a new pump which had a split delivery. This was known as the 6+2 pump which had six cylinders delivering to the steering and only two cylinders worth to the suspension. In normal use this is ample to maintain suspension losses, but pumping up a collapsed suspension would take an age. Answer? stop the suspension collapsing - hence the anti sink system.

Derek

This post has been edited by DerekW on July 15, 2007 05:26 pm

[Peter.N.]

Hi derek

Interesting but seems a bit self defeating. Why replace a proven system and have to spend more money compensating for it?

Peter.N.

[DerekW]

Peter, do you really have to be told? It's a Citroen! Seriously, it does have advantages, it's just that I can't think of any at the moment. Deletion of the priority valve?

Derek