Xantia Rear Height Corrector Adjustment

[citroenxm]

actually... if you never touched the clamp in the first place yur better off re adjusting the height corrector valve itself.... which is possibly why its lost its postiioning... as the mount holes or elongated theres room for position adjustment...

[CitroJim]

Sorry I've made this job sound a bit heavy. It's just me. I'm dreadful at it, I hate doing it and make a right dog's breakfast of it every time

All others clearly find this task a breeze. I don't... Strange but true...

[Mandrake]

Ive VERY sucessfully corrected rear heights with the back on ramps and the front on the ground... Just look at it as though the car is on a hill! It works exactly the same...

Well, I don't know Paul but for me it's never been conspicuously successful but that's perhaps me. I hate adjusting height. Rattiva needs doing and I may well just throw in the towel and go and see Pleiades...

I've always done height adjustments with just two ramps. It's a little bit more tedious but really not that hard and with a bit of practice very accurate.

I start with the car on level ground and measure the ride height from ground to measurement points as per normal to find out how much in error the height is. I then measure from the wheel arch immediately above the front or rear wheel (as applicable) to an easily repeatable point on the wheel - such as hooking the measuring tape on the "lip" of the wheel rim at the bottom side of the wheel, with the tape passing vertically through the centre of the wheel.

I then add/subtract the height error to that figure to know what this measurement should be and note it down. Then I drive the car up onto two ramps to make the adjustment, and take my measurements the same way - from middle top of the wheel arch through the centre of the wheel rim to the lip at the bottom. (Remembering that when the car is on ramps this will no longer be vertical!)

Once I think I have that right I drive it down off the ramps for a final measurement to the ground to verify. Never failed me yet. Once I know the guard to wheel rim measurement for the specific car and rims I generally just do that and don't bother measuring the ground measurement anymore.

One other little trick to get the most accurate result - measure the height that the car settles to both when raising and lowering and take the average, as it will be up to 10mm different each way, and the half way point between upwards and downwards correction is the correct one, not either of the individual measurements. (There is some deliberate hysteresis in the height correctors to stop them constantly fiddling with the height...)

I also find that the height correction is not as accurate if you move it over the full travel using the manual height lever, especially downwards, on models where it can drop rapidly. Best approach is to press the suspension down by hand about 2 inches until it lifts it back up then release, when the car then drops down again, this is your "downwards" measurement. For the other direction I lift the car a couple of inches by the bumper (easy if your spheres are well gassed ) until it starts to get heavy then release, when it rises from this condition this is your "upwards" measurement, then I take the average.

I get very repeatable measurements this way that come out within 1-2 mm each time.

As for the actual adjustment itself, for the ride height I never touch the fine adjustment, I just do it by the clamp on the roll bar. (Some older citroens never had a fine adjustment ) If the ride height is quite close I will slacken the rollbar clamp bolt but not quite enough that it will come loose and move then simply give a gentle tap to the edge of the clamp with a small hammer and screwdriver so that it will very slightly turn on the roll bar, (a just visible movement) then tighten the bolt again.

When tightening the bolt I make sure to have the spanner / ratchet bar at right angles to the roll bar so that the spanner torque doesn't shift the clamp!

After each small adjustment I do the push down and lift test described above and re-measure. About 10-15 minutes usually does it, and I'm quite fussy about ride height. (I find even 20mm out in one direction makes quite a big difference to ride and handling, so I aim for +/- 5mm of spec)

[6speedmanual]

Being a bit of a suspension set up fiend, I too like to get my height correctors and ride heights set right.
Doing it one end at a time is fine if you use the relative difference measurements method described in this thread. Mandrake's description is good, especially his calculating out the averaging effect from an upward correction and a downward correction.
To make the measurement easier, I use a long spirit level (not for the spirit level function, but because it is stiff and has a measurement scale on one side) I rest this against the bumper and measure to the top of the number plate or a piece of tape on the back bumper. When the car is on level ground, it set the measuring "stick" vertically and when the car is up on ramp at one end, leaning the stick to the same angle as the car is pointing "uphill" or "downhill". Otherwise just as Mandrake.
The reason this works on a hydraulic car but not on a conventionally sprung one is that the height corrects irrespective of load. On a conventionally sprung car driving it up a ramp at the front moves weight onto the back axle compressing it further that it would be at normal ride height. Also the hydraulic height adjustment is not load sensitive, so whereas to set the ride height in (say) a Caterham 7 one has to ballast the car to represent the driver weight and do it on a very level "flat" floor. In a Xantia you can equally set the car ride height laden or unladen. All it is doing is controlling the angle of rotation of the ARB to the subframe.
Good luck