Citroën has always been known as an innovator, devising technology and cars well ahead of their time. Sometimes this backfired, particularly in terms of its famous hydraulic suspension systems.
“Nothing but trouble,” they would be dismissed by mechanics (the guys who preceded ‘service technicians’), mainly because they themselves couldn’t take the trouble to learn about the systems with the funny balls at each wheel.
That the essential idea was a good one is shown by how the company persevered with it, continued to refine and develop it, and in its Hydractive 3 form underpinning the new flagship C5 have something still unique, elegant, and so reliable that it only needs servicing every five years.
What makes it work so well now is the advent of sophisticated electronics and enhanced hydraulics, which allows the system to react much faster and much more precisely to running conditions. In-car computerised management systems these days can almost anticipate upcoming bumps and irregularities from the minute instant reactions of a driver’s foot on the accelerator, using the so-called ‘fuzzy logic’ by which modern automatic transmissions ‘learn’ an individual driver’s characteristics.
Anyway, they’ve produced what they call a Built-in Hydraulic Interface as the heart of the latest Hydractive suspension. Along with a few other tweaks, this means that the C5 has automatic height adjustment which does its thing while taking cognisance of a number of different conditions, including vehicle speed and road surface.
If the roads are fairly level, the car is maintained at a normal ride height up to around 65mph. Any faster, provided the road is still good, and the ride height is lowered so that the car is aerodynamically more stable and fuel efficient. But if the BHI senses that the roads are bumpy, by the kind of movement the suspension is making, it raises the car’s height, increasing clearance without compromising handling or comfort.
If the driver is engaged in ‘sporty’ driving, the system also senses this and firms up the suspension as required. This setting can also be selected manually with a switch, though comfort is still maintained during more restrained driving periods.
Of course, the latest Hydractive 3 system also keeps the car constantly level, regardless of load.
Citroën put their money where their hydraulic spheres are. They guarantee that the system under normal use will not need any service for 200,000 kilometres. Compare that to a standard suspension system, where many components really should be replaced in about half that distance.
Disgruntled mechanics will be even less gruntled, with that bit less to complain about.
May 2001
by Brian Byrne
