What Is Active Suspension?

The vast majority of cars on the road today do not have active suspension, so it is not a concern for most drivers. But just as electronically-controlled features like advanced driver assistance systems have become standard on more and more new cars at all price points, it is likely only a matter of time before active suspension is available on most new vehicles.

Let’s take a look at what active suspension is, how it works, symptoms of a bad active suspension, and the active suspension repair process.

A brief history of active suspension

The earliest version of active suspension appeared in 1954 in France, on the Citroen DS. It was followed by the 1957 Cadillac Eldorado Brougham, and the 1961 Mercedes-Benz 300SE. Active suspension’s next step forward happened in the 1980s, when it was adopted by the Lotus and Williams Formula 1 racing teams and became a computerized system. Although it was eventually banned from Formula 1 for being too successful, vehicle manufacturers did extensive research and developed computer-controlled active suspension systems for their high-end production cars. The results appeared on vehicles from Toyota, Lexus, BMW, Mercedes-Benz, and Land Rover during the 1980s and 1990s.

Since the turn of the 21st Century, more sophisticated and faster-reacting active suspension systems have been introduced by Mercedes-Benz, Porsche, Audi, and Nissan (on the GTR sports car). Some of these systems can even compensate for crosswinds. Today, you can buy a Ford Mustang or a Chevrolet Camaro that has active suspension as standard equipment. Just as with many other innovative automotive features, active suspension is working its way down from expensive luxury cars to more affordable vehicles.

What active suspension is and what it does In the “passive” suspension systems that most cars have, the shock absorbers, struts, and springs react to the road’s bumps and potholes as the wheels hit them, with no ability to prepare for them in advance.

But active suspension systems have the ability to control the vertical movement of the car’s wheels. An active suspension’s sensors and computer controls constantly monitor the movements of the suspension, the body, and any feedback from the stability control and anti-lock braking systems, all in real time. The system can then adjust the settings of the shock absorbers and/or the springs, to minimize the effects of road irregularities, adjust the car’s ride height, and soften or stiffen the ride and handling. In addition to the default computer settings, some vehicles provide driver-selectable settings for different driving and road situations.

The benefits of active suspension include:

• Softer ride on bumpy roads
• Flatter ride without body roll when cornering hard
• Lower ride height when cruising at highway speeds
• Higher ride height when driving off-road
• Level ride height when carrying a heavy load
• No nosedive when braking hard
• No rear-end squat when accelerating hard (in a rear-wheel-drive car)

Some active suspension systems use a camera to view the road surface ahead of the car, letting the computer know in advance of any potholes, bumps, or other road problems ahead. This allows the active suspension to plan its responses to these things, before the wheels encounter them. Some systems even have the ability to prevent a wheel from dropping into a pothole, or to raise a wheel to keep it from hitting a bump. The result is a smoother, more controlled ride than any passive suspension system could provide.

Symptoms of a bad active suspension

A problem with your active suspension can be very dangerous. Because your active suspension controls the movement of your wheels and tires, your ability to control your vehicle can be affected. A bad active suspension could potentially cause a loss of control and result in an accident. Many factors can cause failure of your active suspension. Here are some of the warning signs of a bad active suspension:

• Suspension warning light on dashboard illuminates
• Unusual noises heard when hitting bumps
• One side, end, or corner of the car sits higher or lower than normal
• Hissing noise (if suspension uses air springs)

Repairing a bad active suspension

Because an active suspension is made up of a combination of mechanical and electronic components, a thorough troubleshooting process is required to determine the exact cause of the problem. Your mechanic will check the suspension for any mechanical-type wear or damage, and will also check the suspension computer with the appropriate scan tool, to see if any electronic trouble codes have been triggered. Once the source of the bad active suspension has been found, repairs can be made to return the active suspension to normal operation. A wheel alignment may be necessary once that the repairs have been completed.

Don’t try to repair a bad active suspension yourself

Unless you have had extensive experience in working with sophisticated automotive electronic systems, as well as suspension repairs, leave this to the professionals! Your active suspension must be properly diagnosed with the proper tools, and the electronic part of the diagnostic process is not always straightforward. In addition, the active suspension must be deactivated while it is being jacked up or raised, so that it does not try to adjust or level itself during the repair process. The suspension may also need to be disassembled to replace any defective parts.

If the active suspension repair is not done properly, you will have the potential for additional suspension, wheel, or tire damage – or worse. Your mechanic has the proper tools and equipment to repair your active suspension safely and efficiently.