Sphere Shelf Life.

DickieG · Unread post by **DickieG** » 10 Mar 2007, 11:43

I visited Euro Car Parts yesterday to buy a few new genuine sphere's for my V6 as they offer some of them from as little as £21. However when the parts guy brought them out I was somewhat put off by the date of manufacture showing them as being FIVE years old

(apparently all of the genuine sphere's they have are old stock from this period). As a result I decided to go GSF at Heathrow and buy Amtex ones which were just a month old.

Do sphere's have a "shelf life"?

When I commented on the date of manufacture and that the sphere's may well be have lost their gas, the reply from the parts guy was interesting "Well Citroen suspension needs re-gassing every now and then anyway"

AndersDK · Unread post by **AndersDK** » 10 Mar 2007, 12:17

Has been discussed before here on forum.

Do a topic search and you will get the old postings up. Some of our good chemical & physics brains here on board have discussed & explained the real facts behind the sphere design.
The conclusion was to the positive side : spheres have a much longer shelf life than you would first think of.

Unread post by **citroenxm** » 10 Mar 2007, 18:20

Anders / dickieG

I'm not so sure about that..

I purchased 4x Amtex spheres last week, when they arrived TWO had something like 21/9/06 on them and the other two had 12/2/07 on them!

So, upon fitting them yesterday, on a NON Hydractive 1994 SX car, I put the 2007 pair on the rear and the 2006 pair on the front, Result?? Yes the rear pair were TWICE as soft as the FRONT pair, the fronts feeling as though there werent as much pressure in them as the rears!!

So in my experiance YES there is a shelf life, and I'dpersonally give them NO MORE then 12 months for a good continued service on a car.

Regards
citroenxm

slim123 · Unread post by **slim123** » 10 Mar 2007, 18:36

When a sphere is in use the reason for loss of pressure is down to grahams law (a quick google will explain if you are realy bored) this is diffusion of the gas (nitrogen) through the molecular structure of the diaphragm.

As a rule of thumb, 10 bar per year in the front and 5 bar per year in the back (the front being hotter)

On the shelf, the diaphragm is pressed up hard against the wall of the sphere, now we are talking diffusion through the diaphragm and also through the steel. It aint gonna happen.

The shelf life of a sphere is years and years and years.

As for the old stock Amtek spheres, have you checked the pressure? I bet not, if they are down it will be a fault rather than "past the sell by date"

Regards
Slim.

Mandrake · Unread post by **Mandrake** » 10 Mar 2007, 19:59

citroenxm wrote:Anders / dickieG

I'm not so sure about that..

I purchased 4x Amtex spheres last week, when they arrived TWO had something like 21/9/06 on them and the other two had 12/2/07 on them!

So, upon fitting them yesterday, on a NON Hydractive 1994 SX car, I put the 2007 pair on the rear and the 2006 pair on the front, Result?? Yes the rear pair were TWICE as soft as the FRONT pair, the fronts feeling as though there werent as much pressure in them as the rears!!

Huh ? I'm confused, what were you expecting ?

Did you expect the front suspension to be as soft as the rear for a bounce test ? Aint gonna happen! It's NORMAL for the rear suspension to be softer than the front - a lot softer.

The rear suspension has a different amount of mechanical leverage between the pistons and wheel movement than the front, and also much less load weight. The end result is that even though rear spheres have lower gas pressure (30 vs 55) because of the above two factors the rear will be much softer to a bounce test.

If you went and fitted IDENTICAL spheres to the front and rear (which it sounds a bit like you might have) this will exagerate the difference even more.

You can't possibly expect to compare two sets of spheres by putting one lot on the front and one lot on the rear...you might as well screw apples onto the front sphere mounts and oranges onto the rear ones...

Regards,
Simon

Unread post by **citroenxm** » 10 Mar 2007, 20:09

Huh,

Well looks like I was wrong then!

I hold my hands up!

Mind you, if oranges and apples make a better ride, then I'm up for it, they're a bit cheaper to buy!

Regards
citroenxm

AndersDK · Unread post by **AndersDK** » 10 Mar 2007, 20:32

A hydraulic suspension Citroen will always be softer on rear - if all is ok.
And so will most coil sprung cars be too

Unread post by **alan s** » 10 Mar 2007, 23:32

I think some of you guys need to live down here for a while to see just how long spheres will last in a real life situation.
I recently scrapped a couple of CX spheres that were regassed by Pleiades (Australia) about 6/7 years ago, God only knows when they were made.
I fitted a new set on my 16V a few years back which had a made by date of 1994 on them. I still have them on the car and have had them regassed once since.
It seems we now at last may be able to buy reasonably priced spheres, but up until recently, it wasn't unheard of for owners to be charged up to A$285 per sphere.
Imagine that with an Activa!!

Alan S