Different Spheres and my poor old clutch :(

KP · Unread post by KP » 20 Sep 2007, 15:14

Well the rear spheres are starting to die a horrible death and I'm thinking when it comes to replacement to put on some new spheres intended for the 1.6/1.9SD front end as they are the lightest front ended xantias out there(bar the usual 1.8lx ones that people use) as they will give a much softer ride at the rear as i often have kit in the car for work and other bits and bobs it must wiegh about half or just less than what a 1.6block would wiegh.

Has anyone tried this?

Also my clutch is on its way out, or the release bearing to be more exact with a high biting point and juddering grab as the clutch is dis-engaged. Does anyone know what kind of rough cost id be looking at for it to be replaced?

Ps im near doncaster if it helps with the clutch stuff

Unread post by **RichardW** » 20 Sep 2007, 16:50

Hmm, I wouldn't put fronts on the back - they are potentially quite different. If you want to improve the ride with the back loaded up, it might be worth fitting estate spheres - these have bigger capacity so they don't go as hard when loaded up.

The parts for the clutch are about £120 (Valeo clutch kit, release arm bushes, input shaft and seal, diff seals, proper gear box oil) at GSF (and dealer for some parts). Add the garge's margin onto this, then you need to add in at least 6 hours labour, and you're into > £300 territory

Not the end of the world to DIY if you can get access to a chain hoist or similar.

slim123 · Unread post by **slim123** » 20 Sep 2007, 17:34

Personaly, I would stick with saloon rear spheres on the rear.

Front spheres have a harsher damper and a higher pressure to cope with the extra weight (engine etc) although the bypass hole in the center of the damper is slightly larger. I have never put fronts on the back but I guess that the results would not be good.

Estate rears have the same volume as saloons (400cc) but the damper again is slightly harsher to cope with loads and the pressure is higher (30- saloon 40- estate) the bypass hole is also bigger in the estate sphere. My guess is that if you put the estate spheres on, you will find that the mudflaps scrape at the rear, everytime that you pull away.

The estate rear also has a thicker anti roll bar than the saloon and the suspension cylinder has a 37mm piston as opposed to a 35mm piston in the saloon, all these things need to be taken into account when fitting different parts.

By far the softest set up is standard saloon rears, I honestly woudn't bother playing around trying to find a better ride than designed.

The trouble is that we all get used to our spheres gradually going down and eventually we decide that it is time to sort it, when this time come we sometimes try to improve and sometimes do think that we have finished with superb results, but the fact is that anything would be an improvement on knackered spheres and if only we had stuck to the proper parts for the job we would have been just as pleased with the results, maybe even more pleased!!

Well thats just my opinion, of course others may differ?????????

Regards
Slim.

citronut · Unread post by **citronut** » 20 Sep 2007, 19:12

i put front spheres on the rear of a GS estate many moons ago, every time i even looked at the throtle the rear end would dive right down to its bump stops with no efort at all
regards malcolm

Mandrake · Unread post by **Mandrake** » 20 Sep 2007, 20:17

One sentence - don't do it.

Don't put front spheres on the rear, ever. Their gas pressure and damping valves are completely wrong for the rear. You'll get an extremely soft wallowy unstable ride and rear suspension that bottoms with the slightest touch of the throttle.

Just because you might be carrying as much weight in the rear as the front doesn't mean front spheres are suddenly suitable on the rear - not by a long shot.

You are completely ignoring the different purchase ratios of the different hydraulic rams and suspension arms - the front having a direct acting McPherson strut with a 22mm ram, the rear having a 35 or 37mm ram acting against the leverage of the rear suspension arm - the different ratios mean that it requires DIFFERENT gas pressure and damper valves to get the SAME ride with the SAME load weight.

As an example of this - the reason why the estate has 40 bar spheres at the rear instead of 30 bar, (and also has LARGER damper bypass holes) is not directly because its an estate and carries more load, but simply because it has 40mm rams instead of 37mm rams, and the larger diameter rams affect the purchase ratio, requiring more gas pressure and a softer more open damper valve to give the SAME ride as the hatchback.

Just fit the correct spheres and you'll be amazed at how good they are compared to what you remember - because the ride deteriorates so gradually you get used to the poor ride and its not until you replace them with new ones that you realise how much the ride has been suffering...

Regards,
Simon

AndersDK · Unread post by **AndersDK** » 20 Sep 2007, 22:22

Simon - what exactly do you mean with "purchase ratio" ?
Its the word "purchase" used in this context that puzzles me ?

I have an idea that its related to the ram piston diameter (area) and pressure induced to move the loaded ram piston.

Mandrake · Unread post by **Mandrake** » 21 Sep 2007, 05:55

AndersDK wrote:Simon - what exactly do you mean with "purchase ratio" ?
Its the word "purchase" used in this context that puzzles me ?

I have an idea that its related to the ram piston diameter (area) and pressure induced to move the loaded ram piston.

Sorry, poor terminology on my part.

I mean the ratio between hydraulic pressure and force exerted at the wheel - which is a function of both the hydraulic ram area, and the leverage of the load-bearing suspension arm. (If any - which there isn't for a McPherson strut, but is for the rear trailing arm)

These two ratios are very different for front and rear suspension, hence the incompatibility between front and rear spheres in terms of appropriate gas pressures and damper calibrations.

Regards,
Simon

AndersDK · Unread post by **AndersDK** » 21 Sep 2007, 12:53

Thanks - nothing new then 8)

Unread post by **Peter.N.** » 21 Sep 2007, 13:11

....and for your clutch problem - try lubricating the linkage, especially the the top bearing of the shaft that goes into the gearbox bellhousing. If that doesn't do it, slip the clutch for about 30 seconds, but not under heavy load, you dont want to burn it out.

KP · Unread post by KP » 21 Sep 2007, 14:57

Ill whip the filter box off and see if i can reach the linkage there and try and put some lube in there if thats the point you mean?

What would slipping the clutch do?

Unread post by **Peter.N.** » 21 Sep 2007, 15:08

Yes, that's the place. the shaft connected to the cable lever, run some oil around the bush, several applications may be needed. On the XM there is also linkage on the other end of the cable where it goes through he bulkhead, I dont know if the Xantia is the same.

If the bush is dry and tight, it will give the symptoms you mention, but another cause can be the surface of the clutch plate being rough, this can cause it to 'grab' as it is engaging, slipping it will smooth it off. I have had this problem with several XM's and I think, in my case anyway, its due to continually pulling away without using any revs, which the high torque allows you to do - it wouldn't happen with a petrol engine!