C5 front suspension too stiff

[careca]

Just ordered new front spheres 57Bar this time, instead of the 52 i have at the moment. Curious to know how it will ride after i have them installed.

[aerodynamica]

Hello,
the two wheel spheres should actually always correspond to the original spheres because they not only have the correct tare pressure but, more importantly, contain the correct dampers for the respective vehicle. And original spheres also have a better triple diaphragm.
Replica balls often do not have this, because these damping elements do not always fit perfectly for reasons of storage and only have a single diaphragm.
It is true that a moderate increase in the pressure of the wheel spheres softens the suspension - new original spheres therefore have a slightly higher pressure - around 3-5 bar. Higher pressure manipulation of the wheel spheres - more than 5-8 bar per sphere - does not make sense.
However, a softer suspension - especially on the front axle - can be achieved by increasing the pressure of the ball on the harder ball. There are no damping elements on this ball, which should never actually be changed. The pressure of the ball on the hardening regulator can be increased up to 100 bar. In principle, any open ball can be used here - including those from the pressure accumulator of previous models - as these are also easier to fill.

Donors can find out which original balls are correct by entering the chassis number (VIN) in the forum.
Greetings Wolfgang

I agree about moderate increase in pressure to achieve a softer ride but I think the pressure increase must be moderate. I feel that 100 bar is too high because that pressure is too near to the fluid pressure holding the front height in static condition. The nominal fluid pressure of the front suspension of most Citroëns is in the range of about 90bar (accounting for static loads being assumed) and the sphere pressure must be lower than this fluid pressure. The reason is that the sphere internal fluid-to-gas volume ratio must hover around 60% gas volume to allow the road wheels to drop down into road holes etc. If the tare pressure is too high (and too near the fluid static pressure) the fluid will not compress the gas volume enough to allow downward deflection of the wheels. Unless you add more load/ passengers that increases the static fluid pressure but that's not practical.

I learned this the hard way because I fitted CX front spheres (75b, 500cc 1,9 damper) to the front of my then, BX16TRS that would have had spheres of (55b 400cc 1,9 damper). The result was that if I pushed the bumper down by hand, the movement felt very soft and I was really pleased. I went for a drive and found the ride was really poor. If the wheels met a bump that was 'upwards' there was a pleasant sensation. But! Any time the bump was 'downward ' like a pothole, there was a horrible crash sensation. I wasn't sure why at first because I thought "bigger, 75b spheres should be really plush right"? , it was only after refitting the BX spheres back that I wondered if the pressure of CX front spheres was actually too high. Some basic calculation using axle weight and the diameter of the suspension piston revealed that a BX16 has only about 90b LHM pressure when standing, add driver there is barely a significant change. Using the fluid pressure discovery, you can do a second simple calculation of Boyle's law/ mariotte's Law to find the corresponding sphere gas volume for when the car is standing. I realise the pressures were too close and that the original spheres for any Citroën model have a pressure range that is matched to an expected fluid pressure range.
It's also the reason you can't use front spheres at the rear but you can get away with rears on the front. Although the ride will be hard.
I'm not trying to be a buzz kill but I honestly recommend only fitting spheres that are close to the original pressure.

[lcwin]

Hi , If your c5 is H3 which only have 2 sphere in front you can use about 63 bar sphere from non hydractive xantia. It become softer but handling is less. The damping orifice in the C5 sphere is different for bump and rebound which actually give the C5 better handling as well. My previous Xantia I use C5 sphere which make it handle much better.
If you have H3+ with 3 spheres then its much easier . Just change the centre sphere to a higher pressure one or remove the centre sphere damper or drill the centre hole bigger. It will make the C5 smoother but you sacrifice handling especially steering response. The 2 side sphere I wouldn't change as it mainly affect the hard mode.
Enjoy your ride.

[Kees]

XANTIA has no 63 bar sphere, i think you mean the XA75FA.
I know one person who put them on a C5X7 as corner sphere's in front and is satisfied with it.
You're wrong about the corner sphere's that they mainly for the sport/hard mode.
In normal drive all sphere's in the front as in the back are connected to the stiffness regulator together, so in front 3, and back 4 pieces.
Also in the sport mode is this the case!!
Depending on road surface, and a few other parameters the stiffness regulator switched off the center spheres only in the sport mode this will happen sooner.
Greetings,
Kees.

[lcwin]

Sorry my mistake about the sphere pressure. To be honest I haven't touch the xantia spheres for many years after using the C5 spheres. It being use as a lorry for few years now. OK the front center sphere contribute more than 70% softness you encounter in a C5. If you don't believe me try installing hydractive + 3 front spheres in a non 3+ hydractive and see.
Xantia hydractive feels softer to a C5 because its center sphere don't have a damper in it.

[baanb]

@Steve:
You're right about me with a led on the stiffness regulator.
I was thinking about how i could change the system to make it so, that it had a more delay before it changed to the stiff mode.
Finally i disconnected both stiffness regulator's and put a resistor on the connector to prevent errors.
This means that my car is now always has the smooth mode, and I'm happy with it.
Greetings,
Kees.

Hi,

I was thinking about the same thing, disabling the firmness regulators. Can you please share more details how you've achieved it without getting errors?

Thanks

[Kees]

@baanb:
You have answer in your pb

[lcwin]

Simple, just unplug the center sphere connector n replace it with a cheap power resistor of about the same resistance of the regulator. Sorry I don't remember the value . You can measure it with a multimeter. Without power the stiffness regulator is by default in HARD mode.
I wouldn't bother though, just do a push down test on one corner with the engine running. Then stop and lock car wait 10 mins or more and test push down again. This will be the hard mode. With engine running at idle its usually in soft mode

[Kees]

You make a mistake, the stiffness regulator is ALWAYS off, this means, it switch on with a supply of 12 V, also in the hard mode, when the situation requires hard mode by the road surface or other parameters then it wil get the 12 V supply.
The resistant of the stiffness coil is 8.5 Ohm when it's cold.
For that reason i use a resistor 10 Ohm/10 Watt, because the resistor must disapait the 12 Volt.
Greetings,
Kees.

[cit-rotti]

...and please don't forget:
The car from ‘careca’ has no stiffness regulator

[careca]

It is not just pressure, the internal orifice/washers are as important with spheres....

Indeed. Take a look. New ones (correct ones - 57Bar) on the right. It's now smoother, but not as much as i'd like, it's still nothing like my old xantia, but it is overall smoother than before the swap.
What do these numbers near the orifice mean?

BTW took the oportunity to replace the dust boots on the front, and i don't know how people usualy do it, but i didnt remove the strut, only removed the top nut, and then slided the rod down, replaced everything and pushed the rod up from the wheel well.

[aerodynamica]

Hi, I just caught this thread once more. Is this picture of your new pair of spheres? These appear to be mismatched - have they arrived in the same box like this?

The one on the right side has a damper orifice of an appearance I have never seen.

I may have misunderstood the picture combinations.

[careca]

Hi, the right one is the new one and correct for my car, left is the one i removed.

Best regards

[Kees]

I think, the right is original with a small pin across the little hole, to prevent people to drill this one with a bigger diameter.
The left one is this possible and by this way, change the damping of the sphere.

[careca]

How good of a job does a pin really do, to prevent drilling?
On a side note, it's interesting how the car now tilts backwards when accelerating, when before it did not.