Comfort Spheres, All aboard HMS XM . . ?

[ThwartedEfforts]

Hello all,

Just retrieved my XM from a long old service!

As part of the overhaul I've had the comfort spheres fitted and the car now see-saws along roads where there is undulating or bumpy tarmac. The effect is most obvious at night where you can see the headlamps panning up and down the road ahead.

While the car is still tight in corners and can be driven at speed along twisty lanes, the whole experience above 40mph is more like piloting a boat than driving a car

The see-saw effect is barely noticeable at low speeds, such as when manoeuvring, and when the car is driving round town where the roads tend to be flatter. Putting the car in sport mode helps a great deal.

Does anyone have any thoughts on this? Is that part of what comfort spheres do? I thought they may add for a little more movement fore and aft (look, I'm talking in nautical terms already) but it's actually a bit much for me. I swear I just got out the car feeling sea sick.

Any thoughts appreciated!

Phil.

[Andmcit]

Are the new spheres just on the corners or the middle ones
on each axle too?

I'd not be surprised if you've just had the corners done as these really ought to be left alone and
remain stock standard! To get a softer ride BUT retain good roadholding you should concentrate
soley on the middle spheres which will give the suppleness you're probably after.

Andrew

[kenhall1202]

I run my XM on AMTEX comfort spheres, bought from GSF, and am on my second set. However I did have similar see-saw problems when I fitted the first set. It turned out that although the two rear corner spheres were supplied with the correct part number the central orifice in the dampers was way too big. GSF sent me replacements by return and this sorted the problem out. If the back end is unduly 'soft' then you might have a similar cause.

Ken

[ThwartedEfforts]

Many thanks for the replies guys. This is what I have from GSF (GSF part no's shown):

N45304 AMTEX ACCUMULATOR SPHERE x 1
N45322 AMTEX SPHERE-FRONT CENTRE x 1
N45326 AMTEX SPHERE-FRONT COMFORT x 2
N45354 AMTEX SPHERE-REAR CENTRE x 1
N45360 AMTEX SPHERE-REAR COMFORT x 2

The back does seem as Ken describes and is how I imagine a large damping hole would feel. In traffic, pushing the brake makes the car sit up abruptly at the back; taking your foot off to trickle forward makes it sink back. It's VERY soft.

All that said, I must say that a five mile drive round town just now revealed that you can't provoke a see-saw by dabbing the throttle or the brake in turn. In either case, the front or back will compress but it quickly returns to normal height and does not repeat the motion. And as I said in my first post, the car goes beautifully round corners

I'm guessing that it has to be the 'wrong' type of road where, taken at a particular speed, a succession of dips and/or bumps combine to make the car floaty/boaty. I wonder if the country lanes that form my commute are just wrong!

Phil

This post has been edited by ThwartedEfforts on November 14, 2008 09:32 pm

[steelcityuk]

I bought a set of Amtex comfort spheres for the white 2.1 'saloon' I had. I removed them after 4 days and sold them to Lez. It made the car feel twice as big as it had before. Despite the obvious ill treatment by it's previous owner (including a strut through the bonnet) it had the most wonderful ride when the strut tops were replaced and a full set of GSF spheres fitted.

Steve.

[ThwartedEfforts]

Thanks Steve. I may do the same. I need to get a proper night's sleep and drive the car some distance tomorrow to properly assess my feelings on the spheres - am washed out and in need of sleep at the moment so any rocking motion is going to feel twice as bad as it otherwise would. Appreciate all the feedback here.

Andrew, may end up sending the Comfort spheres back or leaving the thing in Sport mode. Right now I think I prefer the original ride

[jorgy9]

Hi Phil

It all depends on the centre orifice size the new spheres came with.

I had front corners with this measuring 1.2mm in diameter when the XM's original for the front corners is about 0.5 to 0.7mm depending on model. I didn't like the car although it was very comfortable on the straight line. And this was without the middle spheres in the game -I later understood that they were inactive-. So in effect I was driving a "CX-XM" or "BX-XM".

If u remove a corner sphere and measure the centre hole, you'll know. I reckon you have to add no more than 0.1mm increments on your corners if u wanted to make it softer.

But best is to have a fully working original suspension.

There's also some choice in the softness u can achieve, using original Cit specs: e.g. there are 2 versions for the front centre sphere, one is 75bar/450cc and the other 70/500cc bar. Softness is similar as such, but if u take a 500ml and inflate it to 75 bar it will add lots more softness. Similarly, for the corners, there has been a sphere, for the "V6 from 1993-1994", that was 450cc/40bar, when all other XMs before and after had 400cc, in various pressures/dampers. If u buy such a sphere and inflate it to 45-50 bar, it'll be very soft so ur car will feel less unpleasant when, in city, u sometimes get the "hard mode" at crawling speeds. There's a risk that perhaps the damping will be higher in those spheres as they were destined for the V6 so maybe at the end the result will be the same.

Still it's amazing what fine tunning one can do just with original Citroen-specification parts just if u research the issue a bit more. On what other car can you do this?

cheers
George

This post has been edited by jorgy9 on November 15, 2008 02:33 am

[Peter.N.]

Strangely enough I had the same experience when I fitted comfort spheres, as you say, the headlights were showing a lot of pitching. This shouldn't be the case if they are a matched set as the damping rate should remain be equal but softer. As the spheres got older the effect lessesed, I have just replaced them with another set after about 60k and the ride is fine with these, so I would also suspect a mismatch.

The numbers check out OK. Have you got full movement on the suspension on all four corners? Just ocured to me that you could have a duff sphere - it does happen


Peter.N.

This post has been edited by Peter.N. on November 15, 2008 12:21 pm

[Andmcit]

It won't be the first (or probably the last!!) time the guys in GSF sell the wrong spheres.
It'd be worth checking exactly what numbers are on the ones fitted to the car Phil.

Andrew

[dean]

Yep been there, i had 1 wrong sphere sent, always, always check the part number stamped on the spheres before fitting!

D

[DerekW]

I've never trusted comfort spheres as they rely on softer damping.

As George and I have written on numerous occasions, there is no substitute for bigger volumes/higher pressures. And your first port of call should always be the hydractive spheres in the centre.

Derek

[Peter.N.]

Hi Derek

Softer damping is what I like, makes it feel more like the CX. Is there anything you can do to the centre spheres to improve the ride then? I didnt think they had any damping.

Peter.N.

[Andmcit]

You can chop and change the sphere in the centre as they're the basic design without jet like
the accumulator. Various pressures and sphere volumes are available and the Activa uses a
whole gaggle of accumulator type ones.

My guess as I've not consulted any handy tables as I'm on my internet mobile, is bigger 500 volume
if there is such a size, and highest pressure available if not regassed 5bar higher.

There is a disc mounted in the centre sphere block that can have the diameter of the jet machined to
a wider size if done carefully with a lathe etc.

I'd certainly go this path than compromise the handling set up soley relying on the corner
spheres.

Andrew

This post has been edited by Andmcit on November 15, 2008 07:49 pm

[Peter.N.]

What do I need with the centre sphere to give a softer ride then? and where can I find your sphere table?

Thanks
Peter.N.

[DerekW]

Yup, as Andrew suggested, a 500cc sphere at 70 bar is about the best you can do.

The dampers are of course in the valve block rather than the sphere itself so you would have to be a bit of a masochist to try to alter them.

Derek