CITROËN AUSTRALIA
TECHNICAL INFORMATION

ACTIVE ROLL CONTROL SYSTEM

PHASE 1 - FIRMING UP ANTI-ROLL BARS

Xantia Activa features anti-roll bars which automatically and almost instantaneously switch from soft to firm settings, effectively doubling their stiffness when the car enters a bend.

Both the large diameter 28mm front and the 25mm rear anti-roll bars are connected to the suspension arms by a gas-filled sphere, which provides cushioning to give an extremely comfortable ride during normal straight-ahead driving conditions. In effect, the 28mm anti-roll bar is operating more like a 23mm one.

As Xantia Activa enters a bend, this anti-roll sphere is immediately isolated, removing all cushioning influence on both anti-roll bars and firming the lateral suspension by effectively doubling the stiffness of the anti-roll bars.

As Xantia Activa exits the bend, the anti-roll sphere is reconnected, and cushioning of the anti-roll bars resumes, halving their stiffness for maximum comfort.

Throughout this process, the normal Hydractive II suspension is unaffected, ensuring that optimum ride quality is maintained at all times, even when the anti-roll bars are in stiff mode.

The isolation of the anti-roll sphere is activated by the same computer which controls the Hydractive II suspension system. This computer receives information fed through sensors continuously monitoring vehicle speed, steering wheel movement, and speed of steering wheel rotation.

PHASE TWO - ACTIVE ROLL CONTROL IN ACTION

In a sustained bend, where body roll may occur despite the stiffnes of the large-diameter anti-roll bars, the second phase of the active roll control suspension automatically brings into operation two hydraulic rams, one at the front and the other at the rear, to level the car.

	Conventional car	Xantia Activa

The high pressure flow of fluid to the hydraulic rams is controlled by an anti-roll connector, similar in design to the unit used on all Xantia models,to control ride height. On Xantia Activa, this corrector, which is connected to the front suspension arms, detects body roll, and adjusts the flow of hydraulic fluid to the rams.

If the corrector senses roll of more than half a degree, fluid is fed in or removed from the hydraulic rams, instantly adjusting the roll bars to compensate for roll and keeping the Xantia Activa level.

On exiting the bend, the corrector returns the hydraulic rams to their normal straight line driving settings. Under extreme operating conditions, not representative of normal road use, the levelling action may be reduced for safety reasons, to forwarn the driver that they are approaching the car's limits.