Airbag Suspension Systems - Part One

 

For too long coil and leaf springs have been the suspension systems of choice in mass produced cars and light commercials. Well, look out because airbag suspension systems have the credentials to take over the scene!

Airbag suspension does away with a mechanical spring and employs a heavy-duty rubber airbag that can be inflated by an in-car compressor or an external pressure source. In most instances, air suspension systems retain the services of a damper to control wheel movement.

The advantages of air suspension are numerous.

Most importantly, air suspension makes it easy to adjust ride height/level to maintain optimal ride, handling and safety – even if you’ve got a two-tonne race car hitched onto the rear. Spin-off advantages are improved tyre life, constant headlight aim and potentially increased bump travel as coil bind becomes a thing of the past. And, as you’ll see in the second part of this series, you can also go for airbag suspension to achieve that belly-on-the-ground low rider look.

Let’s visit Queensland’s Airbag Man to check out the different types of airbag suspension and their applications.

Stand-Alone Air Suspension

A stand-alone air suspension system replaces your vehicle’s current spring and bump-stop setup - only the standard dampers remain. These full-blown systems deliver maximum ride height/level control and can improve ride quality compared to a conventional suspension system.

In a strut system, a donut shaped airbag is fitted around the damper and replaces the coil spring. This requires a custom top mount and a modified strut body to accept the base of the airbag. We’ll detail an airbag conversion in Part Two.

An airbag conversion is generally easier where the spring and damper are mounted separately. In this case, the airbag unit is installed on the chassis and suspension using heavy-duty bolt-on steel brackets. No welding is required.

Airbag Man markets its stand-alone airbag kits under the ‘On-Air’ banner and high-quality Firestone airbags are used. These can be safely pressurised to 100 psi and systems are engineered to comfortably cope with the vehicle’s maximum load rating. Airbag Man’s On-Air set-ups are often installed together with an in-cabin control system for at-a-touch ride level control. The control system is tailored to suit but usually comprises a 12V piston compressor, pressure vessel, rubber lines with brass fittings, solenoids and in-cabin switchgear. A pressure gauge and ride height sensors (for preset ride heights and auto levelling) can also be included.

Depending on the type of vehicle, a stand-alone On-Air suspension system sells for around AUD$4500 – AUD$5000 plus fitment. Exact price will depend on the type of compressor, tank volume and whether you go for ride height sensors and auto levelling.

OE Air Suspension Systems Air suspension is nothing new in production cars but, typically, it is reserved for high-end luxury saloons. In this application, it’s the perfect way to achieve in-car adjustable ride/handling as well as maintaining a constant ride height and level. Airbag suspension is available in cars such as the Toyota Soarer, Crown and Celsior, Audis and even Mercedes-Benzes dating back to the ‘60s. Clearly, there are some recognised advantages to air suspension systems but, equally, it’s obvious there are some durability issues. The owners of Toyota models will know the airbag struts are prone to failure (typically leaks) after about 15 years of use and new OE replacement parts are extremely expensive. It’s for this reason many airbag systems are converted to conventional spring/damper systems. This photo shows a 1990 Toyota Crown with none-too-subtle airbag problems...

Airbag Assistance

If you’re interested in carrying a moderately heavy load without spending several thousand dollars, it may be possible to add airbag assistance to your existing suspension system. Airbag assist systems are compatible with coil and leaf spring suspensions (not struts) and are ideal for four-wheel-drives, utes, light trucks and vans.

In the case of a coil sprung vehicle where the damper is mounted separately, the airbag is inserted within the coil windings. There’s no mounting required as the airbag is free-floating and captive within the coil. A polyurethane protector can also be fitted at the top and bottom of the airbag. Airbag Man sells their coil spring airbag assist systems under the Coil-Rite name and employ a polyurethane airbag (as seen here). The polyurethane airbag can be inflated to a maximum of around 90 psi though there’s rarely any need to exceed 30 psi.

Airbag assistance can also be added to leaf spring suspension systems. Airbag Man offers their Ride-Rite system which use heavy-duty Firestone airbags and require custom mounting brackets on the suspension and chassis. Inflation pressures up to around 100 psi are possible but, again, there’s generally no need to go so high.

With an airbag assist system, you can retain the standard springs and inflate the airbags as required or, alternatively, you can change the spring rate and alter airbag pressure to suit. This is a big advantage in vehicles where the factory springs are too much of a compromise for everyday use – they’re often stiff enough to manage a load but too firm for comfort.

Coil-Rite airbags can be purchased in basic kit form (including airbags, mounts, pressure fittings and lines) from around AUD$245. Ride-Rite airbag assist systems for leaf springs fetch upward of around AUD$800 due to the different type of airbags employed and the requirement for mounting brackets. Both of these systems are designed for manual inflation – you can connect a portable 12V compressor or venture to your local service station tyre pump.

Alternatively, you can step up to an in-car control system which comprises a compressor, pressure vessel and switches. In-car pressure gauges are also available and you can integrate ride height sensors for auto levelling.

So these are the different types of airbag suspension systems. Stick around for the second part of this series – we test drive a Holden ute equipped with a stand-alone On-Air airbag system!

Contact:

Airbag Man +61 7 3889 6556

www.airbagman.com.au