Electronic Air Suspension

Electronic air suspension, often abbreviated EAS, replaces conventional steel coil or leaf springs with air springs whose pressure is regulated electronically to control ride height and keep the vehicle level. It is found chiefly on luxury cars, large SUVs and off-road-capable models, where Land Rover in particular has made it a signature feature. The appeal lies in its versatility: a single suspension system can deliver a soft, settled ride, automatically compensate for heavy loads, and adjust its height to suit conditions ranging from a high-speed motorway cruise to a rutted track.

At each corner an air spring, essentially a reinforced rubber bellows, supports the vehicle's weight on a cushion of compressed air rather than a metal coil. An onboard electric compressor and a reservoir supply that air, while a network of valves controls how much air enters or leaves each spring. Ride-height sensors at each wheel continuously report the vehicle's attitude to an electronic control unit, which adds or releases air as required. By adjusting the pressure, the system changes both the height of the car and, to a degree, the stiffness of the springing.

The most immediately useful benefit is automatic self-levelling. Whatever the load, a full complement of passengers, a boot full of luggage or a heavy trailer on the towball, the system inflates the springs to restore the car to its design ride height. This keeps the headlights aimed correctly, preserves suspension travel and braking balance, and prevents the saggy, tail-down stance that a heavily laden car on steel springs would adopt. The ride quality remains consistent regardless of how the vehicle is loaded.

Variable ride height is the other defining capability. On rough terrain the system can raise the body to increase ground clearance and improve approach and departure angles, allowing the vehicle to clear obstacles or wade through deeper water. At speed on the motorway it can lower the body to reduce aerodynamic drag and lower the centre of gravity, improving stability and economy, and many cars drop to a low access height when parked to ease entry and exit. More sophisticated adaptive air systems combine these height functions with continuously variable damping for even finer control of ride and body movement.

The sophistication comes with a maintenance caveat. Air suspension has more components than a steel spring, and several of them wear with age. The rubber air springs can perish and develop leaks, the compressor is worked hard and can fail, and the valves, sensors and lines are all potential fault points. A leak or a failed compressor can leave the car sitting low or unevenly, and repairs are typically more expensive than replacing a coil spring. For owners of older luxury vehicles this is a well-known ownership cost, but for many it is a price worth paying for the breadth of capability that EAS, as a development of basic air suspension, brings to a single car.