What is air suspension? Benefits & Drawbacks

Pneumatic suspension is fitted to a surprisingly large quantity of cars, including expensive off-road vehicles. Yet, automotive air suspension requires annual checks and maintenance. Consider also that neglect of one component can damage other parts, leading to a much higher repair bill. If you drive a car with an air suspension fault, it can also be dangerous. Therefore, being aware of how air suspension works and catching faults early can benefit both your wallet and your safety.

What is air suspension?

Automotive air suspension replaces conventional coiled metal springs with pneumatic-filled bags that support the vehicle's weight.

The benefits and drawbacks of air suspension

Benefits of air suspension

Self-levelling is a major advantage. This not only stops the vehicle from looking as though its suspension has collapsed, when carrying heavy weights, but it also preserves optimum suspension geometry and handling characteristics. This can be especially useful when towing. Some less expensive cars, such as the pre-2013 Citroën C4 Picasso, employ self-levelling air suspension on the rear axle alone.

Self-levelling systems can alter the ride height, especially on performance cars. Aerodynamics and fuel consumption can be improved, by bringing the car closer to the ground automatically at higher speeds. Conversely, off-road vehicles also benefit from the owner being able to raise the suspension to clear obstacles.

Air suspension drawbacks

Air suspension is more expensive to repair and maintain.

Many types also require specialist knowledge to identify faults and repair them cost-effectively.

What is the difference between air suspension and hydraulic suspension?

Try not to confuse air suspension with hydraulic suspension. Air suspension uses air. Hydraulic suspension uses fluid.

Some manufacturers employ both systems. For instance, Mercedes-Benz's AIRMATIC utilises pneumatics, whereas the faster-reacting ABC (Active Body Control) employs hydraulics.

How does air suspension work?

The air springs are flexible air bags, produced mainly from a special flexible rubber material. Air is pumped into them by an electric air compressor and the vehicle height is regulated by electronic sensors. Air pressure flows in-and-out of an electric valve block and the whole system is regulated by an Electronic Control Unit.

Note that an air strut contains an integral damper (shock absorber); an air spring does not.

What is adaptive air suspension?

This system employs electronics that monitor inputs, such as steering angle, road speed and ride height. Where required in certain conditions, such as under heavy cornering, the system will control air pressure to pump up the required springs, to reduce body roll and improve handling.

Maintenance tips

If you are not mechanically minded, the main tip is to have any dashboard-indicated fault addressed as soon as possible. Most problems are caused by air leaks. Ignoring them can cause premature wear of other components (such as the compressor).

Again, you do not need to be an expert to check if the system is healthy. Walk around the vehicle and check if any one corner looks lower than the others, after an overnight stop. If you notice more than a 2.5cm difference, measured between the top of the tyre and the bottom of the wheel arch, contact a garage.

Routine maintenance checks depend largely on the requirements set by the car manufacturer. Therefore, prioritise those instructions. GEM recommends an annual inspection of the rubber air springs.

Any perished air spring should be replaced in axle pairs; do not wait until they have holed. Damaged, or leaking, pipework should also be renewed.

What goes wrong with air suspension?

Leaks

Air leaks are the most common issue and can occur anywhere within the pressurised system. This causes the air compressor to work longer to compensate.

Air springs perishing

Being made from rubber, air springs deteriorate naturally. When perishing develops into splits, air leaks occur. Remember, air springs should be renewed in axle pairs.

Compressor overheating

When leaks occur, the compressor has to work harder, for longer. In many cases, the suspension ECU detects a fault and cuts power to the compressor. However, this results in the suspension depressurising to its lowest ride height, making the car unsafe to drive.

Air line leaks

The various air lines that link the system together can develop leaks from physical damage. Compressor air lines can also melt, should that component overheat.

Compressor relay sticking

A failed relay also causes the compressor to run continually and overheat. This explains why it is advisable to replace the relay at the same time as a compressor.

Dampers

Air suspension systems tend to utilise conventional shock absorbers ('dampers'), too. These fail in the usual manner. Not only do they become less effective over time but they also can develop fluid, or gas, leaks.

Like air springs, failed dampers should be renewed in axle sets to preserve safe handling and braking.

Our accompanying blog on air suspension shows the most common checks and repairs that you can conduct.

How much does it cost to repair, or replace, air suspension components?

This answer depends entirely on your make and model, the type of fault and the ability of your garage to pinpoint the fault accurately. It is also worth comparing prices between genuine manufacturer parts and those made to equivalent standards by a quality supplier.

It is worth noting that Arnott is a well-established quality supplier that makes replacement air suspension parts but redesigns certain aspects to make fitting quicker, easier and, therefore, less costly.

Can I adjust the ride height of my car with air suspension?

Check your owner's manual for instructions on raising ride height and heed any driving instructions, accordingly.

FAQs

How does air suspension work in cars?

The ultimate role of suspension is to keep the road wheels in contact with the ground. Suspension does this, by using a combination of springs (whether pneumatic, or made from metal), rubber bushes and dampers/shock absorbers.

Why are vehicles fitted with air suspension?

A more comfortable ride is the main benefit. The cushioning effect of compressed air, contained within a flexible air spring, insulates the cabin more effectively against bumps, vibration and noise. This reduces driver discomfort and fatigue.

More sophisticated systems incorporate active damping to reduce the front end from dipping under braking. It also controls the car from rolling to one side excessively, while cornering hard.

These advantages are in addition to self-levelling, described earlier.

What does air suspension help to protect?

Ultimately, air suspension is designed to better protect the passenger compartment from jolts, vibration and noise.

Is air suspension better than shocks?

Air suspension tends to utilise the conventional dampers/shock absorbers as used in other suspension systems.

Can broken air suspension be converted to conventional metal suspension?

It is more usual to convert cars with air suspension to conventional coils, as a cheaper option than repairing the original faulty system. Kits are available for specific models. However, as this is a modification, you must inform your insurance company.

There are also some kits to convert cars to air suspension, especially for show cars. Do your research, before committing yourself to a conversion, especially if it is safe to use on the road.

If you have any specific air suspension questions, GEM's Technical Team can help you. You can send us a technical query, or call 01342 825676 (Mon – Fri, 9am – 5pm).

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