drop suspension mod on xantia

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Post Reply
zorgman
Posts: 95
Joined: 22 Feb 2004, 16:38
Location: United Kingdom
My Cars:
Contact:

drop suspension mod on xantia

Post by zorgman »

just drove up a1m and nice empty roads so i had a play with the hieght lever and moved it 1/2 way tween lowest and norm i could see the car drop via change in headlights beam but noticed how much more stable the car felt so tried it on a roundabout with my son holding lever in place it felt like a train on tracks no body roll.
so then had a look at what keeps the lever in its place its only a notch. doing this mod will give me zero, mid normal, normal, intermedite and full jack.
Now this is the bit i need to know??
will doing this mod have any adverse affects on the suspension or anything else to that fact as when i put my alloys on and the tinted windows itll look better sitting a bit lower (got to tart it up a little bit)
so put thinking hats on and give me some comments please
Richard Gallagher
Posts: 803
Joined: 31 Oct 2001, 02:36
Location: South Bucks
My Cars:

Post by Richard Gallagher »

Basicaly the problem you will have is that the suspension will be riding on its bump-stops. When you go over a bump in the road this will cause an uncomfortable ride, but more worryingly when cornering at speed the car will start to roll to the point where the suspension runs out of what is now a short length of travel causing a degree of vehicle instability.
When 'sports cars' with normal springs are lowered the springs are replaced with shorter but stiffer ones so that when the suspension runs out of travel, the rate at which the car is rolling is therefore reduced due to the stiffer springs.
If you have ever had the misfortune to ride in a boy racer special where the standard coil spring has been cut down to a shorter length to lower the ride height you will know what I mean.
Yes, the car may appear to be 'more stable' when you tested it earlier, but should you find yourself in an emergency situation requiring you to apply coarse steering away from danger the the car will be less stable.
What you could do to improve matters is to fit 'harder spheres' to reduce the roll rate.
ScottFromNZ
Posts: 116
Joined: 17 Feb 2004, 09:27
Location: New Zealand
My Cars:

Post by ScottFromNZ »

I have wondered about doing a similar mod on my BX. That is making a new notch in the height control settings a bit lower than standard as I think my BX on "normal" setting is a little bit higher than what it could be. I have tested it and it is within normal height specs at normal. I think an extra notch slightly below the 'normal' setting would help handling a bit. BUT you don't want to go too low or it will be hitting the bump stops.
Stempy
Posts: 1626
Joined: 26 Feb 2004, 23:21
Location: Cloud Cuckooland
My Cars: C5 V6 Mk1 assainated by wife
Renault Kangoo 1.6 auto, tarted up and remapped
Still missing the Xantia V6
Not missing the AX
Contact:

Post by Stempy »

Or find a nice Activa[:D]
You could have a fiddle with the height corrector settings to bring it down a bit but like Richard said you'd really need to fit uprated spheres to compensate, or perhaps you could get yours pumped up harder, though you'd also have to consider the damping rate which is controlled by an orifice within the sphere.
User avatar
Kowalski
Posts: 2557
Joined: 15 Oct 2003, 17:41
Location: North East, United Kingdom
My Cars: Ex 05 C5 2.0 HDI Exclusive 145k
Ex 97 Xantia 1.9TD SX 144k
Ex 94 Xantia Dimension 1.9TD 199k

Post by Kowalski »

If you get your suspension to bottom out i.e. hit the bump stops, whilst cornering, e.g. by hitting a bump mid corner, you will experience some unpleasant handling side effects from lowering your Xantia. The previous generation Corvettes were notorious for running out of rear suspension travel mid corner and going off the road backwards.
If you lower your suspension you HAVE to stiffen it up considerably so that you don't bottom it out on bumps.
zorgman
Posts: 95
Joined: 22 Feb 2004, 16:38
Location: United Kingdom
My Cars:
Contact:

Post by zorgman »

hmm good advice here and things i hadn't thoght about.
as its an easy mod im going to do some measuring with the car and see what ive got onto the bump stops just for the hell of it as its not going to harm car as the norm position will always be in the same place ill just put another notch in the plate
will report back about this matter so others can follow or know not to try good job ive got a mate with a scrappy so i can get the plates
alexx
Posts: 462
Joined: 19 Nov 2002, 02:42
Location: Slovenia
My Cars:

Post by alexx »

Well, on modern cars including Xantia, bump-stops are soft and progressive, so lowering the car a bit will help killing body roll without affecting roadholding. When I bought my Xantia half a year ago, front was about 1.5 cm below correct height (which is halfway between highest and lowest), and rear about 1 cm. Recently, I set the correct height. Can't say it improved the comfort, only body roll is more prominent (not only in the bends, but also on some uneven roads). Roadholding is similar though. I would say it's safe to go up to 2 cm below the normal height.
As another fact, both C5's I tested last year (hydractive and non-hydractive one) were set even lower. On C5, rear arms are just touching bump stops on the normal height! And - the car lowers more than 1 cm at high speed.
But, since your Xantia is '96, I'm not sure whether it have progressive bump stops on the rear like mine ('98). Older models have stiff rubber rear bumps stops, while newer have yellow progressive ones, made from PU. Rubber bump stops won't like the lowering. All models have progressive front bump stops. Models from 2.0 and 1.9 TD up also have additional hydraulic bump-stops inside front suspension cylinders.
Fitting 'harder' spheres (with lower pressure) will help killing body roll only on hydractive Xantia. On non-hydractive one, left and right suspension cylinders are always connected, so LHM flows freely from one side to other. That's why roll-bars on the Xantia are quite stiff.
I'm not sure is it possible to 'make another notch in the plate', like in BX, because it's made from plastics.
zorgman
Posts: 95
Joined: 22 Feb 2004, 16:38
Location: United Kingdom
My Cars:
Contact:

Post by zorgman »

tried it over weekend on different roads and yes it stopped body roll but the ride was orrible ill keep it where it is set now on norm or use harder spheres
User avatar
Kowalski
Posts: 2557
Joined: 15 Oct 2003, 17:41
Location: North East, United Kingdom
My Cars: Ex 05 C5 2.0 HDI Exclusive 145k
Ex 97 Xantia 1.9TD SX 144k
Ex 94 Xantia Dimension 1.9TD 199k

Post by Kowalski »

I wouldn't expect a 20mm drop to make any difference to body roll unless the bump stops were getting involved which would be dangerous. (Dangerous since there is no or very little suspension travel or damping).
The TD has the hardest non-hydractive spheres that were fitted to the Xantia, the hydractive and Activa models have firmer spheres but you can't use these on a non-hyrdractive Xantia.
tomsheppard
Posts: 1801
Joined: 19 Dec 2002, 14:46
Location: United Kingdom
My Cars:

Post by tomsheppard »

The big issue is actually the driveshaft angle. Drop the suspension and ruin the driveshafts...
User avatar
Kowalski
Posts: 2557
Joined: 15 Oct 2003, 17:41
Location: North East, United Kingdom
My Cars: Ex 05 C5 2.0 HDI Exclusive 145k
Ex 97 Xantia 1.9TD SX 144k
Ex 94 Xantia Dimension 1.9TD 199k

Post by Kowalski »

The driveshafts aren't as big a problem as you might think. The driveshafts have to cope with body role during cornering and steering, on normal (i.e. non-self-leveling) cars they have to cope with different loading of the vehicle. They have to cope with the car pitching during accelaration and braking.
Driveshafts can put up with a lot of running at angles, lowering the car would make them run at angles constantly which would in theory give them more work to do, but since car manufacturers produce lowered versions of cars without altering the driveshafts, I can't see it being that big an issue.
What may be an issue is suspension geometry. The Xantia self levels, so the suspension geometry may have been designed so that it does interesting things, when not completely level, to improve ride / handling etc.
If you are going to lower make sure you check out the geometry otherwise you may find your tyres don't last very long and your car may pick up some interesting handling characteristics.
Post Reply