There seems to be some confusion about what air springs can do – and can’t do. Jaco Kirsten spoke to Andre Brink of the Air Spring Supply Company, an importer and distributor of air springs.

An irate reader wrote to us some months ago about the air springs in his Land Cruiser 60 Series compromising its off-roading ability. The air springs, he complained, were negatively affecting his vehicle’s wheel articulation. This caused the rear wheels to sometimes be suspended, causing the vehicle to regularly lose much-needed traction on a challenging bit of track.

Not true, said Andre Brink of the Air Spring Supply Company – it couldn’t have been the fault of the air springs. The probable fault was that the vehicle was fitted with the wrong-specification air springs. As an example he told us that they tested air springs on a Cruiser 60 in their R&D workshop and that they were able to extend 5mm more than the vehicle’s wheels could articulate.

We asked Andre a few questions:

Do air springs decrease wheel articulation?

One of the biggest myths is that air springs “decrease leaf springs’ articulation”. Because the only way that this can happen is that the wrong air springs were fitted – ones that cannot “stretch” the required amount.

With air springs inside coil springs it could affect the upward articulation of a wheel – but not the downward movement. To avoid interference with articulation for such vehicles on technical terrain, it is advised that air springs’ pressure be reduced to 1 bar from the standard 2 to 2.5 bar.

Why use air springs in the first place?

You do it to keep your vehicle’s ride height normal, even if you are carrying a heavy load or towing a big trailer or caravan. The other benefit is that it greatly reduces body roll by making the suspension much firmer. Handling on corrugated dirt roads will also be improved when you carry a load.

Are air springs used to lift a vehicle?

Although air springs can be used with a lifted vehicle, it isn’t used to lift a vehicle as such. Air springs don’t lift, they help to carry load. There are some exceptions. If you need to increase ground clearance or raise the towbar’s height over rough terrain, you can temporarily inflate your air springs – at 6 bar a Hilux’s towbar can be lifted by about 110mm. But one has to deflate the air springs as soon as possible after the obstacle.

What do air springs consist of and how are they inflated?

Air springs consist of purpose-made air cushions that are fitted either between a vehicle’s chassis and leaf springs or inside a coil spring. The simplest and cheapest way of inflating and deflating it is via air valves that are the same as those on tyres. The next step is to connect the air springs with air hoses so that articulation can be enhanced – when one wheel moves up over an obstacle, the air inside the spring is transferred to the opposing wheel.

What more can you do to your air springs?

The next logical step is to fit a compressor to your vehicle so you can inflate the suspension from the cabin by merely pressing a button. You can also have the springs connected in such a way that you can change the pressures individually or the front and rear axles separately. Most people install cabin controls for the rear wheels, because this is where increased loads require most adjustment.

 

How complicated is installing air springs?

It usually doesn’t take more than six hours to install four air springs, a compressor, air hoses and the cabin controls. A more basic set of air springs with normal valves will take about two hours. However, it will take the fitment centre another hour or two to make sure there aren’t any air leaks.

So you don’t have to install everything at once?

No, you can first install a basic set of air springs and have the compressor and cabin controls fitted later.

What do air springs cost?

It all depends on your specific vehicle and your requirements. For example, fitting air suspension to a Hilux’s rear wheels could cost about R4000, plus R400 for labour. Hilux bakkies have McPherson suspension at the front – and they cannot be fitted with air springs.

How long do air springs last?

The sturdy design of the Firestone air springs that my company imports makes them the only ones I would fit to a vehicle’s rear axle, where they would work the hardest. We guarantee the springs for two years, but they normally last 10-12 years. Some owners have done more than 400 000km on a set of air springs, but this all depends on how a vehicle is used or how you treat the springs. If, for instance, you inflate them too hard, a vehicle’s coil springs could “pinch” and damage them. Heat from a vehicle’s engine or exhaust system can also negatively affect air springs and sometimes part of a vehicle chafes against them. But this is usually the case with air springs that haven’t been installed correctly.