Adaptive Air Suspension

Adaptive air suspension is a system that brings together two distinct technologies, air springs and electronically controlled adaptive dampers, so that a single suspension can vary both its ride height and its firmness automatically. It represents one of the more sophisticated forms of ride control fitted to road cars, combining the load-levelling and height-changing abilities of an air system with the moment-to-moment comfort and body control of variable damping. It is found most often on luxury saloons and SUVs, where the breadth of capability it offers is highly prized.

The two halves of the system perform complementary roles. In place of conventional steel coil springs, an air spring at each corner uses a reinforced rubber bellows inflated with compressed air supplied by an electric compressor and a reservoir. By adding or releasing air the system can raise or lower the body and, crucially, keep it level regardless of how heavily the car is laden. Alongside each air spring sits an adaptive damper, typically using a valve or a magnetorheological fluid whose resistance can be changed electronically in milliseconds, so the controller can stiffen or soften the damping to suit the road and the driving style.

A central control unit ties the two together, reading sensors for wheel position, body movement, speed, steering and the selected driving mode. From this it manages both attributes simultaneously: it might raise the car for extra ground clearance over rough ground, lower it at motorway speeds to cut aerodynamic drag and improve stability, firm up the dampers in a sporting setting for flatter cornering, or relax everything for a soft, gliding ride. Because the air springs handle load levelling, the car sits at the correct height and headlight aim whether carrying one occupant or a full complement of passengers and luggage.

For the owner this translates into genuine versatility from one vehicle. A large SUV can ride high enough to tackle a rutted track yet settle low and composed on the motorway; a luxury saloon can cosset its occupants over poor surfaces yet tighten up when driven enthusiastically. Some systems also lower the car automatically to make entry and exit easier or to assist loading.

The sophistication carries well-known costs. Air springs, the compressor, valve blocks and the network of lines and sensors are expensive to manufacture and, in time, to repair. The rubber bellows can perish and develop leaks with age, the compressor works hard and can fail, particularly if it has been overworked compensating for a slow leak, and a failed system can leave the car sitting low or unable to adjust. These are recognised maintenance considerations on older vehicles so equipped.

Adaptive air suspension sits within a family of related systems. It builds directly on plain air suspension by adding variable damping, overlaps with adaptive suspension which focuses on the dampers alone, is essentially the same concept marketed by some makers as electronic air suspension, and depends fundamentally on the damper as one of its two core components.