Join Date: Jun 2007
Location: Warrington Cheshire UK
You are correct in that the sphere is mechanically a citroen sphere.
The only Citroen sphere that comes close to being correct is the Citroen CX front suspension sphere. This has the same 75 Bar pressure as the RR unit.
But...., it is not an accumulator sphere, so it also has a valve and a restrictor hole (I did my homework on this little lot before I bought replacements). This provides the sphere with the 'shock absorber' effect. The valve opens to let the fluid in as the suspension piston pushes fluid up into the sphere (as you go over the 'bump'). The fluid can only escape through this 1.5mm hole as the spring re-bounds after you have traverseed the 'bump'. This slowed down flow stops the oscillation that would occur otherwise.
Use of this CX sphere on the RR accumulator system is debateable. Do you consider that the sphere would need to pass fluid out to the brakes at a rate quicker than can be supplied by the 1.5mm hole?. That is the question, and not having designed the system, its not possible to be sure.
Personally, I would guess that it would probably be OK, but there is always that element of doubt, so the smart move is to buy the right one and accept the price doubling over and above GSF's prices.
The rear spheres are only 15 Bar pressure and definitely a RR special pressure, though mechanically its the same item.
As for the fluid, I use Citroen LHM. Its available much more readily, though I do decant it into the original Castrol bottle, as that fits in the holder in the boot.
I take on board the 'not overtightening' of the spheres on re-fitting. I bought a tool off Ebay to undo the stubborn ones. As I said earlier, my accumulator spheres are mounted awkwardly, so I think we will have to demount the lower accumulator to get the upper sphere off. We reckon we can get sufficient flex on the pipes on the lower accumulator unit to get enough room to do the upper.
I won't be re-building the whole accumulator though. The car has only done 55k miles. I didn't see any special tips on the Australian site, which is an excellent resource for the DIY mechanic.
Red to Red, Black to Black, Blew to bits.