Hi,

I hope this hasn't been asked too often before, but can someone advise me please on the difference between Normal and Comfort rear spheres? Both are listed on the GSF site at the same price. My car's a Series 2 V6 Exclusive Estate (auto) and I'm told all it needs for its long delayed MOT is a pair of rear spheres. It has centre spheres so I'm guessing it has Hydroactive suspension. I'll be changing all the spheres once the car is road legal and I want to make sure whatever I fit now for the MOT will work well with the rest of the new spheres................ Jim.

Hi combwork,

Go for the Comfort spheres.!! They will give you a nice SOFT ride, the normal ones will be a little harder, and are designed for the Hydrauactive system.

Putting comfort ones will not do any harm what so ever!! But may well have a small effect when you switch to SPORT suspension, it wont be as hard in the corners..

Anyway, an estate is a work tool, not a racing car...

I have comfort spheres on my two V6's, the cars still grip just as well!

Hope this answers your quiery

Regards
citroenxm

Hi CitroenXM,

Thanks for your reply. From what I've read, the series 2 V6 Estate has hyrdactive suspension. In your post you say that the `normal' spheres are designed for use with hydractive suspension. The suspension on my car has always seemed a bit harsh; almost as if it's locked in `Sport' all the time, so logically it's a prime candidate for `comfort' spheres. Once I've replaced all the spheres though (including the centre spheres) and hopefully got the hydractive to do its job, is there any danger then that with `comfort' spheres on the rear, it could feel too soft?

I'd appreciate as much information I can get; I have to order up the spheres and have them fitted asap to get the car back on the road.............

Best Regards,

Jim.

[QUOTE=combwork,Dec 5 2006, 20:48 PM]

The suspension on my car has always seemed a bit harsh; almost as if it's locked in `Sport' all the time, so logically it's a prime candidate for `comfort' spheres.

I'd appreciate as much information I can get; I have to order up the spheres and have them fitted asap to get the car back on the road.............






It sounds very much like the "softness regulator" diodes have failed. (There is a thread on this in the "2.5 and V6 section, I think) The age of the car would seem to suggest it as a possibility.
I would not fit the softness spheres if you intend towing a caravan with the full 75 kg noseweight applied.

I will go with citroenxm. I have comfort spheres fitted to my estate and the ride feels something like the CX. If your suspension is overly firm, have you replaced the centre spheres? these are often overlooked but have far more effect on the ride than the outer ones as they are virtually undamped. If you bounce the suspension with the engine running, then turn it off and wait for the 'clonk' from the solonoids, it should be considerably stiffer, if not you probably need new centres. If the suspension is good you should be able to bounce each corner 4" - 6", although it will be stiffer on the front.

Peter.N.

Deal Done

Two `Comfort' spheres ordered from GSF and the car is now insured; guess this means I have to go through with it this time and get it back (road legal) on the road

Wish me luck,

Jim.

Hi Jim

Yea, got an MOT on my 24v so need to get it TAXed and insured next payday and get her moving!!

No point having MOT and not using the beast


Regards
citroenxm

Combwork, could you let us know what the specifications are for your comfort spheres?

The reason I am interested is because, as we all know, there are only three parameters that can alter: pressure, size (volume) and damper settings.

Please bear with me while I think aloud. The dampers are only fitted to damp out oscillations and should ideally only work on rebound. Each one consists of a plate valve with a hole in the centre which closes off a ring of larger holes. On "bump" the fluid being driven into the sphere opens this valve and the fluid flows almost unobstructed through the larger holes into the sphere. On "rebound" the valve closes and the fluid is restricted in its return flow by the small central hole. The damper size that is listed in the specifications is this return hole size so it follows that altering that will not affect comfort.

Because to all intents and purposes, pressure x volume is constant, it follows that if, when hitting a bump, the pressure in the sphere is doubled then the volume must be halved. For comfort you want long wheel movement for a given bump so it follows that this volume change must be as large as possible and that means BIG initial sphere volume. This is the principle behind the extra sphere in hydractive suspension which adds its volume to the leg spheres.

The operating pressure in a sphere when it is supporting the weight of the car is the same irrespective of its initial pressure and can be calculated by dividing the supported weight by the area of the leg piston. This is true even of a "flat" sphere which is presumably at atmospheric pressure. In order to reach a pressure of, say, 1000 Lbs/sq.in it will have compressed to 1/68th of its original valume - which doesn't leave much volume for springing. It can be seen, then, that by increasing the sphere's inflation pressure the intitial compression under load will be less and there will again be more volume available for wheel movement. Perhaps this is the reason for the much higher inflation pressure in the hydractive sphere (On my car 70 bar as compared to 55 bar).

So, if I'm right, for comfort you need the largest spheres you can get, at a higher inflation pressure than standard provided it is less than the loaded pressure. And if I'm wrong I'm sure someone will tell me.

Derek

Hi Derek

I don't know the spec but I can tell you from experience that that the damping is reduced, the orifice, although still small is larger than the standard ones, about a sewing needle compared with a pin, if you follow. In driving it does give a slightly 'wallowy' feel like the CX and the headlamps dont stay level on the road as with the standard spheres. It would probably be to soft for some, but I like it

Peter.N.

Hi all

Citroens hydraulic system was originally designed to make a car FLOAT not to be firm and rough riding like a sports car!

Cannot agree with you more Peter - nothing like a SOFT sprung (or should that be gassed) riding car..

It just makes welsh roads feel so much like a runway!!

Regards
citroenxm

Hi all,

My figure for the front suspension spheres for my car was wrong- trouble with relying on memory. It is actually a 450cm2 sphere at 40bar (not 55), compared with the 50bar that is fitted to all the other late XMs. This seems to prove my suggestion that increasing pressure increases softness!

So what do I do as a V6 owner? I seem to have two choices; fit the standard 50bar spheres in place of my 40's or go for the 500cms x 40bar spheres that are fitted to the rear of non hydractive estates.

I'm looking forward to the next sphere change, I like the idea of those estate spheres!

Derek

Hi

With out a doubt, higher pressures cause a softer sphere.

I remember, I had a Xantia SX TD L reg, non hydrauactive non anti sink, and I had access to a re-gas tool, so I experimented a little and put more then required pressure. I cant remember exactly, but they were BX estate spheres, comfort ones, meant to be 40 bar, and I think I put about 60 bar in them!

Result! I SUPER soft and extreamilly bouncy/ floaty back end. I then found what I could do was use the clutch in traffic and "bounce" the back end up and down simply by engageing the clutch and releasing it!

I also found that if I held my foot on the brake, for a moment or two, then released my foot the back end would DROP to the floor, then foot on brake while the HP pump worked, released the foot brake, then the back would shoot up to high position with the sudden rush of pressure to the rear. Then foot on brake, hold it, and back to the start, bang to the floor....

Ooo how I miss that party trick on that particular car.. those were the days.

I wish I was clever enough to build a re gassing tool, or even find a tool to purchase!

Regards
citroenxm

I suppose that the ultimate would be to use standard non hydractive spheres (if they made them) on the corners and drive it in sport mode, then if you wanted 'super soft' suspension, put it in normal.

Peter.N.

The problem with fitting a larger volume sphere is that its pressure doesn't decrease as fast with car motion as a smaller volume, ie it becomes harder slower. This means the suspension will be "ending" quite easily and often. The ideal is what Peter says, provided u have an Hydractive 1 that can switch between soft and hard. And they do make these non-hydractive XM spheres, u can buy from the belgian manufacturer HFSM (or something), or even other sources. So for your safety it's better to keep the sphere size to the manufacturer's specified, and play with pressure or orifice (comfort spheres).

I have to say though, I have used -without knowing it- comfort spheres, and, although car was very nice and comfortable on the straight, it felt discomfortably vague in twisty roads. Mind u, these were "extreme" comfort spheres: front orifice 1.1mm (instead of about 0.5-0.6), rear 0.9mms instead of 0.7....I don't know what bore the GSF ones come with.

Also, and that's the worse, I have later on realised that those spheres were just masking a problem with the hydractive's function (pressure regulator was out of tune and produced too low a pressure range for the middle spheres to open). When I adjusted this and drove off the ramp, it was a revelation, really. In my opinion the Hydractive XM doesn't need anything else than its standard spheres, if all works as it should on it. It also irons the road as such.

Regards
George