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...
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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
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