TECH TORQUE: AIRBAGS
> MODERN, COMPUTER-CONTROLLED AIRBAGS AREN’T JUST FOR THE LOW ’N’ SLOW CREW. HERE’S WHAT’S INVOLVED IN FITTING AIRBAG SUSPENSION TO YOUR CAR
We take a look at the current state of the art in airbag suspension
WE ALL love seeing a tough car slammed to the ground, but they can be a royal pain to live with. Getting in and out of driveways, over speed humps or down our rough highways without taking the sump, exhaust or undercarriage out is a real challenge, and this is where airbag suspension provides an awesome solution.
Aaron Gregory from Memphis Hell (that’s his ’51 Chev, top right) has been installing air suspension in all manner of vehicles for over 10 years, and he’s seen the industry change dramatically in its packaging and brain-power.
“While Slam Specialties brought out airbags with internal bump stops and springs comparable to coil-overs, the single biggest improvement has been the technology controlling the air systems,” says Aaron. “Companies like Air Lift and the recently defunct Accuair have auto-levelling systems and that make the car much nicer to drive. It doesn’t matter if it’s a nice old full-size Chevy filled with mates and Eskys in the back or a latemodel HSV ute with a tray full of concrete bags, the height management systems will keep the car exactly at the pre-programmed ride height and perfectly level.”
However, while airbag suspension might seem like a quick and easy path to killer stance and improved practicality, there are several important factors to consider before racing out to buy a kit, including budget.
“I have a bit of a niche where people want me to build them a car that sits on the ground, so wheels, drivetrain and engine bay all have to go somewhere and that is upwards, which means lots of fabrication,” says Aaron. “People see you can buy a ‘kit’ for $4500, but that is the cheap and easy part. If you want to get your car engineered, which you should, then you’re over $6000 for a height management and auto
levelling system, so you can’t change the car’s height unless the handbrake is on.”
While he’s long been a member of the Negative Camber mini-truck club, Aaron points out that airbags offer more than just being able to sit your sills on the deck. “It’s not always about going low; sometimes you need to go high,” he says. “Load-assist is another massive sector of the air industry, probably more so than having a car lie flat on the ground. I had a bloke with a ’36 Dodge truck get in contact who just wanted an airbag on the diff with a switch so he didn’t rip his back bumper off when he drove out his driveway with a load on the back.”
In the past there has been concern at perceived difficulties in attaining engineering approval for airbag set-ups, and this has led to some confusion and myths around pneumatically adjustable suspension systems. Aaron has heard them all, and laughs them off. “People say airbags are no good for race cars, but some Pro Mods are apparently now running air suspension,” he says. “They run pumped up through the burnout and, once the tyre has finished expanding, about halfway into the run the bags drop to improve aero.
“One big myth is that you can’t have an air system that doesn’t leak,” he continues. “The system won’t leak if you put thread sealer on your fittings, use DOT push-to-connect fittings and Dot-approved air lines, and cut the air line clean and square. My truck can be parked for three months and it doesn’t move a millimetre.
“You also need to watch for condensation in the tank as that can lead to rust in the valves, which brings on a world of problems. Nothing should touch an airbag, as that will end up rubbing a hole, and air line needs to be treated with the same logic as fuel line: it can’t touch anything.”
Technology has also improved the ease of fitting air systems, in Aaron’s experience, though it is still not a job for a total mechanical novice. “With the Air Lift system I fitted to an S550 Mustang recently, I had one ground, one power and one ignition power wire and that is all I needed to wire in. The rest is all pre-terminated, so you just plug it in. You have to be super-thorough with the installation for the Accuair e-level height sensors in terms of measurements and cleanliness, but once you get them done right, they’ll live forever.”