Air springs have only been part of the mainstream rodding scene for about a decade, yet they're already almost as common as dropped axles and whitewall tires. This is not too surprising, considering the benefits they offer in terms of height adjustment, ride quality, and adaptability. As long as low cars are cool, it seems air springs-or airbags, as they're commonly called-will remain popular.
Despite their wide acceptance, we still find that there are many misconceptions about air-spring applications and installation. Some enthusiasts feel the only purpose for air springs is to create a totally slammed, on-the-deck stance. Others consider them light-duty components best suited for show-only vehicles. In truth, air springs are very durable, and have been in use on big rigs and other heavy equipment for decades. They almost never fail when properly installed, and can actually deliver performance-handling characteristics when used in a well-designed and properly set-up suspension.
We recently consulted with the air-spring experts at Air Ride Technologies and Air Lift to ask about some of the most common problems and mistakes they see from customers and installers. They helped us compile a list of dos and don'ts for installing air springs and making sure they work as well as possible. "Most of these items should be addressed when setting up any suspension-air or traditional metal spring," says Bret Voelkel of Air Ride Technologies. "These problems are not necessarily unique to an air suspension, but are simply magnified by the fact that you can manipulate the ride height of the car manually."
DON'T Let an Air Spring Rub on Anything
This seems obvious, but it's a common problem. The air spring cannot contact any other part of the vehicle or it will eventually fail. Failure may occur anywhere from days to years down the road, depending on the contact, but it will happen, and there's never a good time for it to happen. Air Lift recommends at least an inch of clearance between the spring bellows and any other component when the spring is fully inflated. Installers should also verify that there is no rubbing throughout the normal range of suspension motion and steering travel.
DON'T Drive the Car Fully Deflated or Inflated
Every air spring has an intended ride height. The more you deviate from that height, the worse the ride quality and handling will be. The car will bottom out if it is driven too low. In fact, internal chafing can occur in some air springs if they are used with too little pressure. You should also avoid subjecting air springs to regular, prolonged use at maximum pressure, as the ride will be very stiff and can also damage the spring. Voelkel suggests starting your ride-quality tuning at the air spring's recommended installed height and making small adjustments from there, usually 1/2-inch or less in either direction.
DO Pay Attention to Air-Spring Load Capacities and Spring Rates
Even though air springs can have their spring rates manipulated with air pressure, they aren't one-size-fits-all. As Voelkel puts it, "You cannot expect an air spring intended to support a concrete truck to offer good performance on a lightweight street rod, or vice versa." He says double-convoluted air springs typically have less travel and more load capacity to work well in independent front suspensions. Sleeve-type air springs usually have more travel and softer spring rates, which are more appropriate for solid rear-axle suspensions. Using the wrong air spring will result in poor ride quality and handling properties.
DON'T Let the Shock Absorber Bottom Out
When setting up a conventional air-spring and shock system, it's important to make sure the shock absorber does not bottom out before the air spring bottoms out, or before the car is on its bumpstops. This can damage shocks and shock mounts, and create potentially dangerous handling. Shock absorbers can, however, be used as extension stops for sleeve-style air springs. You don't need to worry about the shock bottoming out when using an air-spring-over-shock component, such as Air Ride Technologies' ShockWave or EasyStreet's AirOver Shock.
DO Recognize the Importance of Shock Absorbers and Sway Bars
Air springs tend to have softer spring rates than equivalent metal springs. While this can allow for nicer ride quality, it also requires properly matched shocks and sway bars to ensure good handling. Complementing your air springs with high-quality adjustable shocks will optimize your car's performance potential and allow you to fine tune its handling. (With a ShockWave, the adjustable valving is built in.) An aftermarket sway bar, especially on the front suspension, will optimize cornering characteristics.
DO Assemble Air-Line Fittings With Thread Sealer
A leaking air-spring system can be aggravating, and leaky fittings are probably the number one source of air leaks. Some fittings come with a locking compound applied, but you still need to use a Teflon tape or paste to ensure a tight, leak-free seal on the pipe threads. Air springs and tanks do not leak unless they are damaged, so the fittings are the first parts to check if your system is losing air.
The most common source for air-spring leaks is at the fittings. A little Teflon tape or th
DO Use DOT Air Lines and Fittings
Air lines and fittings approved by the Department of Transportation (DOT) are rated for extreme vibration, abrasion, and temperature. This is the same reinforced nylon line you find under big rigs to run their air brakes. Normal industrial polyurethane lines are NOT intended for such harsh environments. DOT air lines will always have a DOT certification number stamped on it. You can identify DOT fittings by looking for an attached inner sleeve that prevents the line from deforming inside the fitting.
DON'T Plumb Air Springs in Pairs
It may seem faster and easier to "double up" and supply two springs with one air line, but such convenience will compromise performance. Running individual air lines to each air spring prevents air transfer from side to side when cornering. This will help cornering performance significantly, and will also allow you to adjust the air pressure to level the car.
DO Pay Attention to Tire and Ground Clearance
The air-spring ride height must be synchronized with the intended ride height of the vehicle. Additionally, it's imperative that you check ground clearance and tire clearance at ride height, full extension, and full compression to be certain there is no interference between suspension components.
DON'T Expect an Air Spring to Cure Other Suspension Ailments
Air springs can offer many assets to your rod's or custom's ride and handling, but they can't perform miracles. It's important that all other suspension components-bushings, ball joints, shocks, and steering parts-are in good shape, so the air springs can perform to their potential. You can't expect air springs to rectify ride and handing problems caused by a suspension that is damaged, improperly installed, or poorly set up.
DO Check the Angle and Travel of the Driveshaft and Ball Joints
Every part of your suspension has physical limitations that can be affected by significant ride height alterations. Ball joints can bind if they are pushed beyond normal operating angles, so you need to find-and stay within-their limits when setting up your air springs. Likewise, lowering the rearend will affect the driveshaft angle, which may need to be adjusted to prevent driveline shake.
This is what can happen when there are no extension stops in place and a rear axle is allo
DON'T Lay the Car on the Ground
This will probably always be the most ignored rule of air springs. To ensure the safety of you, your passengers, and your car, you should maintain at least one inch of ground clearance when the air springs are fully deflated. Also, make sure you have proper tire clearance when the springs are deflated. According to Voelkel, Firestone double-convoluted air springs act as their own bumpstops because they maintain rubber-to-rubber contact when fully deflated, but other air-spring brands and styles may need external bumpstops to prevent damage when fully deflated. In addition, these other styles of air springs need extension stops to prevent them from overextension. Usually the shock absorber will accomplish this task.