Hi People, new here

[Sim]

Hiya guys,

I've just become the proud owner of a 1.8 16v W reg Xantia saloon, nice silver affair with a spotless interior and engine bay (newest car I've ever owned).

My question is this, my previous Xantia was a 2.0LX, very early one, and sank all the way to the ground on account of the suspension leaked like a seive , me and my mates always used to laugh about how it looked pretty mean when the car was right down, and how it would be cool to go cruising in it.

I never let them for fear of not being able to stop with no brake pressure, but it always got me wondering ... how closely related is the effectiveness of the steering and brakes related to the ride height, could the car be driven in a lowered mode and still be safe, I was wondering if there would be a way to modify the ride height switch to put in a third setting to allow the car to ride lower than normal temporarily.

Before anyone asks yes I am an aging boyracer wannabee, I just never had the money (or car) to play with, so this is more hypothetical wonderings than anything else (I'm saving up for a kitcar now, instead of trying to fit in at Max Power).

[Homer]

how closely related is the effectiveness of the steering and brakes related to the ride height,

Its not. If you set the height lever to lowest the steering and brakes will work as normal.

could the car be driven in a lowered mode and still be safe,

Safe as in nit crashing, yes at low speeds but it would damage the driveshafts or CV joints.

I was wondering if there would be a way to modify the ride height switch to put in a third setting to allow the car to ride lower than normal temporarily.

There was thread on doing exactly this with a BX by simply cutting an extra notch in the adjuster, in theory it should work but to do the job properly and eliminate the risk of damaging the car you need to fiddle with the sphere pressures.

[deian]

Xantia's have a big STOP light in the instrument cluster, this will come on when the car has no pressure, i.e lowered and u press brake, when the car says STOP (in red) it means it! NO BULL NOW OK, you risk dying, and worse than that killing others on the road too.

If this 'STOP' light comes on as u drive, the steering will stiffen up first, then the suspension will lower and you will know this as the car will feel everything on the road and bounce all over the place, and then your brakes. The system is designed to make sure the brakes fail last so you can stop, of course this depends on the condition of your accumulator sphere, if it's bad your brakes will fail a lot sooner. The accumulator sphere holds backup pressure for the system so if it's healthy they say you have enough pressure to brakes hard 30 times.

With the suspension lowered there is NO pressure in the system, i.e no brakes, so NO don't drive with the car on the lowest setting, steering won't work so well either, besides being stiffer because there is no pressure in the system, the wheels will be higher up in the wheel arch and they will scuff the tyres, you won't have any suspension at all.

Anyway... point is, only drive on the normal mode. And for short periods at low speeds on the 2nd high mode. Don't be silly here! The hydractive system wasn't designed for boyracer wannabes. Good luck.

[jeremy]

A W reg xantia will have the twin outlet pump and the anti sink mechanism. Some may have more as well - particularily relating to hydractive suspension.

The twin outlet pump means that the steering is entirely separate and operated by the majority of the pump. Assuming adequate LHM and a sound drivebelt - the systems can be regarded as entirely separate.

The circuit for the brakes and steering is pump, pressure regulator/accumulator, safety valve, front brake circuit/suspension, rear suspension/rear brakes.

The safety valve is a clever thing, and when the light goes out it means that there is enough pressure for the brakes and front suspension. It then opens further and feeds the back.

The front brakes have one tapping on the safetyvalve, and opposite is the tapping for the front suspension. This then passes through the height corrector and then goes to the front suspension.

So - the height of the front suspension is controlled by the height corrector and the height has no effect on the pressure in the rest of the front systems - ie brakes and steering.

The back is a bit different in that the back brakes are fed from the back suspension circuit - so providing a nice system of load compensation.

The difference between Citroen hydraulic suspension and air suspension is that the height on Citroen hydraulic is controlled by the VOLUME of the LHM - and with air suspension the height is controlled by the PRESSURE.

[Mandrake]

I never let them for fear of not being able to stop with no brake pressure, but it always got me wondering ... how closely related is the effectiveness of the steering and brakes related to the ride height,

The steering would be unaffected but with the suspension fully down there would be no rear brakes, since the rear brakes run off the rear suspension.

could the car be driven in a lowered mode and still be safe, I was wondering if there would be a way to modify the ride height switch to put in a third setting to allow the car to ride lower than normal temporarily.

Can the car be driven safely in the existing low position ? NO WAY....it would fully depressurize the suspension, not only would you have no rear brakes, but the car would be riding on the rubber snubbers, and every slightest bump would cause the car to react violently. Driving at open road speeds in this state would entail EXTREME danger. Furthermore you would do serious damage to the front suspension strut rubber blocks in no time flat, even at around town speeds. (They sometimes fail after 10+ years anyway, they don't need any extra help to fail )

Could it be driven safely in a "lowered" (rather than lowest) position ? Thats a matter of debate. It would be possible to cut another notch in the height control lever and if you got it just right you could set the height to JUST above the lower snubbers.

The problem with this is the manually overriden height settings are very inaccurate, and getting it to repeatably achieve the same height would be difficult unless the height correctors were adjusted spot on. You still have the problem that even small bumps will bottom the suspension. You could probably drive it around for short periods of time at low speeds like this but once again it would be totally unsafe at open road speeds. (Just like cars with cut springs are!!)

Regards,
Simon

[AndersDK]

We debated that way of lowering a BX.

The conclusion is that using the method filing an extra notch for the height lever will not work. Because you then disable the auto levelling - and instead set the height to whatever the linkage will find stable in that new position.

Instead you MUST adjust the height linkage for the lower height with the manual control lever in the normal drive position. This also means you will loose the heighest setting (of less importance).

As with ANY car and suspension :
lowering the suspension - and then decreasing the ground clearance - you MUST also decrease the possible suspension excursions - to save your engine's oilsump etc.
This in-evitable means a stiffer setup - as with any sportscar.
On a hydropneumatic Citroen this is done by selecting a LOWER sphere inflation - and a smaller damper orifice. I.e. a totally different sphere setup.
I'll leave any maniacs with a fresh and still sound (possibly young ) spine to search the web for the mathematics involved to find the correct spring constants in the Citroen spheres for such a setup.
From the BX we found out that 30mm lowering was absolutely maximum.
- and that looks a LOT - much more than you may think

- and then we have not yet discussed the issues of the extra stress on driveaxles - because of the sharper working angles on the CV's.

[Sim]

Ok thanks guys, it's nice to finally have this argument settled, me and my buddies have been arguing this point for about 5 years now, they all had nice modified VW Gaffs and I went for luxury rather than sh*t-yer-face-off-speed like them, and they were convinced that it could be done, but I always maintained that they made lowering kits for Xantias as well for FOR A REASON!. Guess I should have just asked the experts

Besides I like the Xantias the way they are, about the only thing I have often thought about was maybe a headlight upgrade and a bodykit (I saw a really cool one ages ago while I had my first Xantia, this bloke had it done as a one off, gave it almost Laguna mk1 lines but more aggressive) anyway that's for another thread.

[jeremy]

I think you can lower a Xantia without any real problems and indeed I think the Activa lowers itself when it detects its running on straight fast roads like motorways. This is to improve stability and lower drag.

I know for certain that some air suspensions such as those fitted to Range Rovers have this feature.

I have explained abve the difference between the Citroen hydraulic system and the air suspension - and so as (within the working range) the height is independant of pressure I don't see that the damping will be affected - or for that matter the rear brakes.

True the steering geometry will change a bit but as its got struts at the front it won't be by much. The driveshafts may be a bit more of a concern - but I would have thought the running angles would actually decrease - however simple observation will confirm - and the shafts shouldn't come apart if the thing is fully raised when the joint angles become quite acute.

What you may find is that even quite a small drop produces a very bad ride. This happens on my BX if the thing doesn't rise to its proper height - and may be due to the struts operating outside their usual range and the slides being rough. I'm not sure what the real reason is.

Obviously all departurers from the manufacturers specification must be at your own risk.

[Mandrake]

I think you can lower a Xantia without any real problems and indeed I think the Activa lowers itself when it detects its running on straight fast roads like motorways. This is to improve stability and lower drag.

Sorry, not the Activa It has purely mechanical height correctors the same as any other Xantia. This feature was first introduced on the C5 with its electronic measurement and control of the height.

I have explained abve the difference between the Citroen hydraulic system and the air suspension - and so as (within the working range) the height is independant of pressure I don't see that the damping will be affected - or for that matter the rear brakes.

Within the linear travel of the suspension, no. But there is quite a signficant percentage of suspension travel (something like 30%) where the rubber snubbers are partially compressed, and at normal ride height you're not hitting the snubbers except in rare occasions.

If you lower the ride height too much you're bouncing off the bottom snubbers all the time even for small bumps, which does upset the effective damping because the rebound force from the snubbers is a lot stronger than the softer gas springing and is therefore not well damped by the damping valves which are calibrated for the rebound forces generated by the gas springing rate.

What you may find is that even quite a small drop produces a very bad ride. This happens on my BX if the thing doesn't rise to its proper height - and may be due to the struts operating outside their usual range and the slides being rough. I'm not sure what the real reason is.

I think you've hit the nail on the head - strut wear. My Xantia used to be like that where a 10-15 mm change in ride height, especially down caused the ride to become much harsher.... since I replaced the strut cylinders the ride is no longer super height sensitive like that...

Regards,
Simon