My stock Citroen BX is equipped with hydropneumatic suspension. I have a ser of xantia suspension spheres mounted which brings the pressure up to 70bar vs the standard 45.
My question is, how does hydropneumatic suspension perform in contrast of conventional suspension or sports suspension? Now don't get me wrong, it's a fabulous sensation and I've ridden few cars as comfortable as this, but does comfort come in exchange for performance?
This depends on the suspension setup. Hydropneumatic suspension (in implementations slightly different to Citroën's) has been used on various sports cars including the MG F and McLaren's current range including the P1.
Citroën's original implementation was biased for comfort, at the expense of body control: after a bump, the system takes longer to settle than most cars. Citroëns also tended to roll quite a bit, although that didn't impair cornering as much as you'd expect.
Citroën later developed hydractive variants (with variable spring rates to improve body control) and ultimately the Activa.
At any time, Xantia Activa rolls at most half a degree. This make it not only spectacular to look at, but also improve cornering speed. French magazine L’Automobile tested a Xantia Activa on skidpad and measured an amazing 0.94 g lateral acceleration. This compares competitively with many supercars - NSX managed 0.93 g, Ferrari 512TR 0.92 g, Toyota Supra 0.95 g and Ferrari F40’s 1.01 g. This is even more impressive if you consider the Xantia wears just 205/55R15 tyres ! Most cars in its class manage around 0.8 g only !
In normal road situations I have never driven a car as smooth as a hydropneumatic Citroen. I have regularly driven a BX and several Xantias and have never thought that they handled any better or worse than a 'conventional' car in normal road situations. I suspect that they are inferior on the track or if pushed really hard.
One to research is the Xantia Activa as it uses a far more advanced system that is supposed to be brilliant and handle great, albeit at the expense of patchy electronics. IIRC an Activa has a higher cornering speed in the swedish Elk test than a lot of properly fast cars (inc the 911, R8, NSX, M3 etc etc)!
