Ride height measuring, can't find point to measure

[charentejohn]

My Xantia is not as other cars............
I did the ride height check and front seems ok, measured to wheel centre etc and arrived at 125mm instead of 121mm so pretty good.

Tried the rears but can't find the point to measure to in the standard measurement diagrams.
This seems to be behind the sphere and rubber mounting and before the flat vertical towing ? plate near the bumper.
In the diagram it is a small projection but I don't have it, all I have ia chassis members with nothing attached, apart from the floor.

Wheel centre height is 300mm floor to bottom of Chassis 425mm to floor near chassis 495mm, neither of which give the 136mm difference I am looking for.
So I used the other method of adding 300 and 136 to give 336mm and seeing if anything fitted, only part of the rear is the dip in the boot floor pan, any good ?

Suspension looks ok but just wanted to do it properly

[Mandrake]

It's the flat section of chassis immediately behind the rubber mount, which is around 5cm x 5cm of flat area. Can you take a picture of yours ?

[charentejohn]

Thanks, I will check it out tomorrow and take a photo if I am still confused.

[charentejohn]

Found it, some wierd and wonderful measurements though, think I am finally there.
Bearing in mind I have just fitted new rear spheres and hydraflush and only driven the car on the road for a mile or so, what I get is.
Did citrobics, rear wouldn't go to low at first but now does, went to all positions twice.
Left engine running and bounced front and rear a few times and left to settle.
Turned off engine and measured all within a few mins.

Both wheels measured 290mm to the centre.
Front measurement to flat area near driveshaft was 155mm so height 135mm instead of 121mm so quite a bit off.
Rear, at flat bit behind engine mount was 430mm so height 140mm within limits of 136mm.

I have done the rear spheres so would doing the front help that drop a little ?
It used to be lower then seemed to creep up a bit to where it is now quite some time ago. So probably nothing I have done recently would have done this.
Would changing front and front centre spheres be likely to correct this ? If not I will drive it a bit and see what happens, I will be doing the spheres in a few weeks anyway, once hydraflush is done.

[Mandrake]

Changing the spheres won't have any effect on the ride height at all, if the front ride height has drifted out of adjustment over time its possible that someone has left the bolt on the height corrector roll bar clamp a bit loose.

For best accuracy you want to measure the ride height with the engine running, and without getting in and out of the car.

Also you need to make two measurements - one after the car has made an upwards correction to reach the correct height, and one after it has made a downwards correction to reach the correct height - then take the half way point between these two readings, because they will not be the same. If the suspension is in perfect working order the two readings will usually be within 10mm but as they age and the height corrector linkages get sticky and/or the plastic dogbone clip wears out they could be 20mm or more different.

On my Xantia the front suspension up/down readings are only 8mm apart (which is good) while the rear suspension is 30-35mm apart, which is quite bad and noticeable as intermittently poor/good ride from the rear suspension as the ride height doesn't settle to the same height reliably.

It will be the linkage sticking due to rust but I haven't been game to pull it out yet when all the pipe unions are rounded off from rust...

[RichardW]

You can remove the rear height corrector linkage and leave the hydrualic unit in place Simon.... Probably not that easy on the car, but I've done it on the spare one I've got in the garage.

[citronut]

it is quite easy to separate the H/C cradle from the H/C in situe,
you must pay attention to how the levers and linkage's intertwines between the cradle, H/C and height rod though,

other than that its just held to the cradle by two 11mm bolts that screw into the H/C body

[charentejohn]

Sounds like a plan, I will check out the height correctors in general then do the measuring up and down as suggested.
Could just be something sticking a bit, I have a can of spray grease handy for such things, sprays on like water so gets in everywhere, the dries as grease. Handy for hard to get ar areas.

Off out for a run today so that may wake things up a bit.
I have been reading posts on the the pressure regulator so will listen for the 'buzz' and stop from the pump. Seems ok as I recall but I will listen carefully, and use a stopwatch

[citronut]

if the height corrector linkage's/turrets are sized up just spraying grease on probably wont do much at all,
as the only way to free them off fully is off the car, and give them a sever lubing and working lubing and working lubing and working lubing and working,

the pressure regulator usually tick's not buzz, i think its the electro valves that buzz,

as you have moved the clamp on the anti roll ber this is probably a lot to do with the height being wrong now,
even if the H/C linkage/turrets are sized which can/will also affect the ride height,

the clamp on the roll bar only requires moving a minute fraction of a gnats dooo daaaa to give quite a difference in ride height

also the car needs to be level and on all 4 wheels to adjust the heights, and so you dont get sqished if it droped on you whilst you are under there,

[Mandrake]

it is quite easy to separate the H/C cradle from the H/C in situe,
you must pay attention to how the levers and linkage's intertwines between the cradle, H/C and height rod though,

other than that its just held to the cradle by two 11mm bolts that screw into the H/C body

Only problem is the height corrector linkage mechanism is full of grease from the last time I greased it, so I can't see any of the levers and linkages to see what I'm doing I'll have to flush the grease out somehow before I can attempt it.

[charentejohn]

I am being careful about falling cars, I can see the problem, remove wishbone or similar and car thinks is is way to high so plummets to the ground.
My local scrap dealer once warned me about working under a tower of cars as he said he didn't want blood on his clean concrete.

I haven't done the correctors yet as still measuring, I am one of these people who has to know if it is right or wrong.
Currently I have made 2 measuring 'sticks' of bits of overlapping wood held with a clamp.
So I have done the up/down bit and then set the 2 measuring sticks to what the height front and rear should be, then compare with what it is.

Strangely, the finger test suggests car is too high, measuring says just about right but slightly low.

[citronut]

if and when adjusting the height by moving the roll bar clamp the car can and will drop rapidly without warning,

the prob i can see here is you might/could have added another variable into the equation by moving the clamp on the anti roll bar,

you should only touch/adjust this if and when you have exhausted all other isues, like sticking linkages/turrets

[charentejohn]

All ok, I haven't adjusted anything - yet, just checking on what could have caused this. If there is even a problem.

I seem to have lots of different figures and observations.
The car looks a little hight to me so I measured the heights, engine off, and they seemed too far out.
I redid it with engine running and the measured readings are a little low if anything, so it should be even higher.

I think all is well and will measure again, and check here, before messing with anything.
The car's hydraulics have had a quite a few problems recently, burst pipes mainly, also air in the system, low fluid level from slow leak, solid rear suspension from bad sphere.
Hence the full revamp, fixed hose leaks, fitted hydraflush, new rear spheres x 3 and bled brakes.
Result is rear suspension now works and brakes are applied with very little pedal movement (I assume that is correct).

Only real things to sort are, now that all is fixed, is the height correct and why does the back not go to low from normal height but only after being on high first.
Once done I can do my 1k miles and put in new LHM.

[Mandrake]

Here are the figures that I got when measuring my Xantia as an example:

Front suspension:

L1=121mm - figure quoted by the manual for model/spec
R1=286mm - measured rolling radius of the front wheel
H1=165mm - calculated chassis to ground measurement in line with the driveshaft

Measured chassis to ground - upwards correction 169mm, downwards correction 161mm, average 165mm. (spot on! and only 8mm of overshoot, which is about as good as it gets for the front suspension)

Rear suspension:

L2=136mm - figure quoted by manual for model/spec
R2=296mm - measured rolling radius of rear wheel
H2=432mm - calculated chassis to ground measurement to the chassis behind the rear rubber mounting

Measured chassis to ground - upwards correction 454mm, downwards correction 420mm, average 437mm. 5mm too high, however the overshoot is a whopping 34mm due to a sticky linkage. This amount of overshoot leads to intermittent poor ride quality particularly at the rear suspension which is constantly trying to compensate for acceleration and braking induced squat.

[charentejohn]

Thanks for the measurements, I have been trying to find my piece of paper with the ones I took, I will post them for comparison when I find it.