Active Body Control

Active Body Control, marketed under the abbreviation ABC, is a sophisticated active suspension system developed by Mercedes-Benz and offered on its most prestigious models. Unlike conventional suspension, which can only react passively to the road, and unlike adaptive dampers, which merely vary how firmly they resist movement, ABC actively generates forces to oppose unwanted body motions. Its purpose is to keep the body of the car flat and level through cornering, braking and acceleration while still absorbing bumps for a comfortable ride.

At the heart of the system is a high-pressure hydraulic circuit. A belt-driven pump pressurises hydraulic fluid, typically to around two hundred bar, which feeds servo-hydraulic actuators built into the strut at each wheel, in series with a conventional coil spring. Sensors continuously monitor body acceleration, ride height, steering, speed and the forces acting on the car, and a control unit commands each actuator to extend or retract. By pushing or pulling on the spring strut many times a second, the system can raise or lower each corner and add or subtract supporting force on demand.

The defining feature of ABC is that it counters body movements actively rather than simply damping them. When the car turns into a corner, the system pressurises the appropriate actuators to resist roll, holding the body almost level instead of letting it lean. Under heavy braking it counteracts the nose-diving tendency, and under acceleration it counters the rear squatting down. The result is a car that stays remarkably flat and composed through manoeuvres that would normally pitch and roll the body considerably.

For the occupants this brings a distinctive blend of qualities that are usually in opposition: the cornering flatness and body control associated with a firm sporting set-up, combined with the supple absorption of bumps expected of a luxury saloon. Because the actuators work mainly on the slower, larger movements of the body while the springs and a degree of conventional damping handle high-frequency road inputs, the system can deliver a level, controlled ride without feeling harsh, and it can also adjust ride height with speed or at the press of a button.

Such capability comes with real-world considerations. ABC is a complex, high-pressure hydraulic installation with pumps, accumulators, valves, sensors and actuators, and as such it demands careful maintenance, clean fluid and periodic attention; leaks or failed components can be costly to put right and may cause the car to sit unevenly. The hydraulic pump also draws engine power, and the whole system adds weight and expense, which is why it was reserved for flagship cars such as the S-Class and the SL.

ABC sits within Mercedes-Benz's wider family of suspension technologies and the broader field of active and adaptive suspension. It is more interventionist than air suspension systems such as Airmatic, which provide variable height and adjustable damping but do not actively cancel body roll, and it shares its ambition with other active roll and tilt control systems that seek to manage how the body behaves rather than merely cushioning the road beneath it.