Hard Rebound

mongoose100 · Post by **mongoose100** » 11 Apr 2011, 06:30

Hi all,

2000 Xantia V6, running non-hydraspastic corners.

When hitting speed bumps etc, the compression is fine however coming down off such things results in a decent thud from the fronts - almost like the suspension cant rebound fast enough. The rear seems more than happy

Could this be caused by centre sphere being flat maybe?

Cheers in advance

Post by **xantia_v6** » 11 Apr 2011, 06:42

Check that your front ride height is correct, an inch too high will cause that. Your soft spheres will make the problem worse and you may need to fit more firmly damped spheres.

Post by **CitroJim** » 11 Apr 2011, 07:00

Yes, I would entirely agree on all counts. My experience of running a V6 on non-Hydractive spheres is that the damping is well below par.

Try, for now, running in sport mode and see if that improves matters. It will be worth running a Lexia or ELIT across your Hydractive ECU to check it's clear of faults and that all sensors are working. It may not be switching to hard mode promptly under braking.

Post by **CitroJim** » 11 Apr 2011, 07:03

Also, forgot to add, sphere damping elements can wear and reduce damping markedly. Pop the spheres off and see if the central rivet and disc is loose on the exposed part of the damper. If so then this is a sure sign the damper has had its day.

mongoose100 · Post by **mongoose100** » 11 Apr 2011, 07:10

Cheers for the replies, it was just as unhappy on a know good set of standard fitment spheres.

Looking at the front tho, she does seem marginally high. Does that mean I begin the fun task of altering the ride height???

mongoose100 · Post by **mongoose100** » 11 Apr 2011, 07:18

CitroJim wrote:Try, for now, running in sport mode and see if that improves matters. It will be worth running a Lexia or ELIT across your Hydractive ECU to check it's clear of faults and that all sensors are working. It may not be switching to hard mode promptly under braking.

Sport makes no noticeable difference to the thud - however, it does firm things up quite nicely in corners ets. My view is that it is super sensitive in relation to switching to hard too

Lexia shows no faults in Hydractive ECU.

braking shows no signs of nosediving etc.

Curious tho, how would 1.9TD Hydractive spheres feel like???

Post by **CitroJim** » 11 Apr 2011, 07:37

Hydractive 1.9TD spheres should be absolutely fine... I'm not aware of a special V6 fitment..

Ride height adjustment is not such a bad job as long as you can do it on a ramp, have all four wheels under load and the car level...

Do ecxclude everything else though before playing with ride height...

mongoose100 · Post by **mongoose100** » 11 Apr 2011, 07:44

Cheers Jim.

So, assuming centres have nothing to do with this issue?

Post by **CitroJim** » 11 Apr 2011, 08:00

mongoose100 wrote:Cheers Jim.

So, assuming centres have nothing to do with this issue?

No, as the car should switch to hard on braking/deceleration and this will isolate the centre sphere. Damping in my experience is strictly in the province of the corner spheres and the centre sphere is there only for comfort!

Johnny Cogs · Post by **Johnny Cogs** » 10 May 2011, 11:44

OOOoooo ekkk, I think I have made a booboo.... I had to get my hands on some spheres quick and have grabbed a pair of fronts from a 2001 1.8 petrol model.

Xant, (i know I should buy knew but wasn't an option at the time) to put on my '95 td VSX estate....

Am I now reading correctly that spheres are differently weighted/preassurised and I am replacing a broken spade with a spoon???

Post by **CitroJim** » 10 May 2011, 12:01

Johnny Cogs wrote: Am I now reading correctly that spheres are differently weighted/preassurised and I am replacing a broken spade with a spoon???

Yes, spheres have different pressures/damping rates depending on their intended application.

Corner (i.e. suspension) spheres all have dampers but the rates differ significantly between fronts and backs. You should never put front corners on the rear corners and vice versa. Likewise Hydractive spheres should not be fitted to a non-hydractive car although vice-versa it can give a slightly softer ride but a bit under-damped.

Accumulator and hydractive centre spheres have no dampers and must NEVER be used on corners. Likewise, corner spheres with dampers must never be used as accumulators or hydractive centre spheres.

Generally, front and rear corners can be experimented with (within the bounds of the above) to see what suits you best. For instance front corners from a 1.8 petrol may give you a subjectively better ride on say, a 1.9TD. Likewise rear corners intended for an estate may give what you may consider a better ride on a hatch or vice-versa.

Providing you obey the fundamental rules as stated above, it can be interesting to experiment with spheres.

Johnny Cogs · Post by **Johnny Cogs** » 10 May 2011, 12:06

Hi Jim, thank you for the quick reply....

So basically, by fitting the fronts off the 1800 to the front of my td estate might give a softer ride (for example) but wont be so soft that I will fail the impending mot test? If that's the case then I will just whack em on there and see how it goes....

Post by **CitroJim** » 10 May 2011, 13:42

That's absolutely correct Johnny. The MOT tester is not going to check absolute damping, just check that there is acceptable damping there. I think you'll find 1.8 spheres will be OK. I know they have been used on estates in the past with happy results...

mongoose100 · Post by **mongoose100** » 27 May 2011, 14:34

Well, tackled the front ride height today, not such a bad job

Some idiot had set the front height via the manual control rod, released that and the car went sky high! Anyway, back to spec and comfort and rebound back to Citroen levels!!!

Now, just need to find out why passenger mirror drops in reverse and doesnt return... Pain in the butt