I don't think weight is the answer, a Xantia and a CX are actually exactly the same weight! (1300Kg +/- a bit depending on the model spec)citroenxm wrote:Hi
A Xantia will NEVER ride as good as a CX or DS, and possibly an XM!
The heavyer the car, the better the ride, as the way it was designed!
The DS was a heavy car and the system was designed for that car.
I think the Computer Control on the XM spoils it slightly.. but its still worlds ahead of Springs and Dampers!!
And dont forget the GS - one of the best riding small cars of all times, is a paltry 980Kg, which is less than even the plastic BX
It's a number of factors IMHO:
* Amount of suspension travel - the CX just has more usable suspension travel than a Xantia, period. At the front its quite a lot more, a couple of inches extra, and it does really make a difference.
(You can fly over wide backed speed bumps with ease in a CX that bottom the suspension in the Xantia) The Xantia only has a similar amount of suspension travel to a GS - a much smaller and lighter car.
The softer the springing is the more suspension travel you need to prevent it bottoming - and a Hydractive 2 Xantia is actually sprung a bit too softly for the amount of travel it has, IMHO, so it tends to nudge the snubbers quite a bit on undulating roads, which spoils the ride and damping.
* McPherson struts vs double wishbones is a no brainer - McPherson struts will always be inferior, and this is probably the single biggest difference between a CX/GS and a Xantia.
Not only does a McPherson strut have a significantly compromised geometry (which matters a lot on a car with soft springing and plenty of travel) but under dynamic conditions of cornering, braking, accelerating etc the static friction of the strut increases, which compromises ride, damping, and tyre contact. McPherson struts are cheap and compact, nothing else.
* Lack of centre point steering - the Xantia's McPherson struts have high KPI typical of struts, (about 13 degrees) while the GS had zero KPI with perfect centre point steering which gave a brilliant zero-kickback manual steering system.
The CX has some kingpin inclination because of the brake disc interference, but gets around the problem with the design of the DIRAVI steering system.
* Unsprung weight - the GS had a real advantage in that the unsprung weight was massively less than typical due to the inboard front brakes. The sprung to unsprung weight ratio is a key factor in ride quality and handling and its especially important for light cars - the GS, being a light car, never would have ridden and handled as well if it had normal discs in the wheels. (The DS also had inboard brakes)
The Xantia has relatively high unsprung weight at the front, (ever tried lifting a new disc?!) but to be fair, so does the CX.
Stiffer rollbars were mentioned for the Xantia, but I don't actually think they are all that much stiffer than a CX - when I had mine up on ramps with weight on one wheel and the opposite wheel hanging in mid air I was trying to tighten the wheel nuts and the wheel was moving several inches just with me pulling on the tyre lever - which would have been twisting the rollbar...
I think the reduced body roll is more to do with the different roll centre of the McPherson struts, and the particular geometry they chose for the CX/GS. (Which has fairly equal length arms, and therefore quite a high roll centre)
Another thing in the favour of the CX for ride is that it has full rubber block isolation between the seperate suspension chassis and the body - something even the GS didn't have, so the CX is very "rumble" free.
Regards,
Simon