Air Suspension Basics for Towing
Take a Load Off
Pneumatic suspension, more commonly called air suspension, has been around since its first patented design the early 1900s. There are many questions about its existence and how it relates to towing. We will only be able to scratch the surface of the topic, but hopefully this will provide insight into the benefits of a properly designed airbag and air supply system.
First off, it’s important to identify your vehicle’s towing and hauling capabilities, which will vary depending on exactly which work truck you’re driving. Inside the driver-side doorjamb, there is a sticker that identifies the VIN and the vehicle’s Gross Vehicle Weight Rating (GVWR), which is the maximum weight your truck can safely carry. This rating, along with your truck’s towing capacity, is determined by many factors, including engine size, gear ratio, wheel and tire package, cab and bed configuration, transmission, and axles, for example. It is important to note that most manufacturers typically advertise their highest towing capacity rating for a given vehicle, which is generally a work-specific setup not common for the average consumer, whose truck is rated for quite a bit less capacity. Always verify your load is within the manufacturer’s specs for your vehicle.
Your truck’s original suspension design allows for safe hauling, towing, and handling characteristics. When fully loaded, though, the weight can shift rearward, aiming the headlights towards the sky, bottoming out the rear suspension, and making the steering lighter and braking more unpredictable. Adding an airbag, or helper air spring, to the system can make a night and day difference in the towing experience, alleviating the aforementioned towing ails by adding support for the load. The result is better overall control of the vehicle. There are many systems available that add a helper air spring to your existing suspension, or entirely replace the stock suspension platform (full air ride) of your truck. The average system places an airbag and corresponding brackets over the rear axle or leaf spring. Versions are also available for coil spring setups that help stabilize from within the inner diameter of the spring.
Once inflated, the helper bag assembly allows you to add air to the system to level the vehicle and add much needed stability, firmly planting all four tires evenly on the ground. This makes a huge difference—even when you are well within your vehicle’s tow rating capabilities. These systems can also help offset the negative effects of sagging springs or worn shocks that lead to poor towing performance. An added bonus is the ability to adjust your tow vehicle’s height when hooking up a trailer. Companies like Air Lift and Ride-Rite offer many add-on air spring systems capable of increasing the stability, safety, and ease for your towing experience.
Can adding an airbag to your existing suspension allow you to carry increased payloads or tow heavier trailers? The simple answer is, no! It’s important to remember that the addition of any airbag system does not allow higher payloads or towing capacity to your current vehicle. You have to take into account that other systems on your truck—including braking and cooling—are rated for specific manufacturer-rated capacity. Exceeding these ratings is not safe and can be a very costly mistake, even with the addition of an airbag arrangement that is theoretically capable of carrying additional weight.
Since an air spring acts like an inflatable (and deflatable) balloon and requires high air pressure to operate effectively, you need the ability to inflate. Generally, more air (higher pressure) cushions and levels the ride of a loaded-down rig, and less air (lower pressure) returns an empty rig to a factory feeling. Onboard air systems are the answer to adjusting air pressure and come in many different variations based on the duty cycle of the system. On the light-duty end, simple inflation valves can be installed on lines that connect to the airbags. These are filled exactly the same as a tire and work well for sustained periods during which static, nonadjustable air pressure is adequate. They can be plumbed together or with individual valves. The advantage to individual valves is the ability to level out a vehicle side to side to compensate for uneven loads. The next step is adding electric or mechanical air valves, a compressor, and an air tank to allow for pressure adjustability on the fly, via in-cab switches. There are many options for a setup like this, including a 12-valve air compressor, a CO2 system, or an engine-driven compressor. With a little bit of creativity, compressors and air tanks can be mounted so that no bed space is compromised. A desirable side-effect to having onboard air for your suspension is the ability to inflate tires and drive air tools if the system if robust enough.
If we had a look at a big rig’s suspension and air system design, we would find a multi-link setup with airbags fed by a very efficient gear-driven engine compressor, tank, and valve arrangement. The system is pressure regulated and maintains a prescribed ride height determined by a valve mounted to the chassis. This valve is actuated by a lever arm connected to the rear end; if the vehicle is loaded and the rear end squats down, the valve opens and adds more air to the airbags until the load is back to normal ride height. This arrangement allows for a light and tolerable ride when unloaded and an equally capable vehicle when fully loaded. Many aftermarket systems are available from companies like AccuAir to mimic the big rig design using a controller and electric valves that can be manually operated to lift or lower a vehicle to a desired height.
So how long do these airbags last? When installed properly and maintained, they will last as long as any other rubber product on your vehicle. Since the air spring is pliable and can be damaged from rubbing or chafing, it’s very important to keep a good amount of room between the bag and any brackets across the whole range of travel. Any contact the airbag makes will shorten its usable life significantly. It’s also important to keep the airbags inflated enough to maintain their shape even when you aren’t towing. Excessive wear can result if the bag is under or overinflated. Keeping air in the bags also allows the vehicle to be put up on a lift for short periods of time for service. If the vehicle needs to be on a lift for a while, it’s best to unbolt the airbags if they are the limiting suspension component. One final note about the airbags is to be aware of their maximum pressure ratings to avoid premature failures.
Airbag setups, both OEM and aftermarket, have come a long way in design and function. With truck manufacturers jumping on the pneumatic bandwagon, it’s clear we will be towing on clouds of compressed air in the not-so-distant future.
1. Factory air ride? You bet! An optional rear air suspension system was introduced on the ’14 Ram heavy-duty trucks. On the 2500, an airbag replaced the coil spring, much like the Ram 1500. Load capacity is not sacrificed and, in fact, ride and handling get even better. The air suspension is also capable of load-leveling, where payload or the load on the rear suspension from a trailer is automatically detected and accounted for. The 3500, while still featuring the rear Hotchkiss leaf spring system, received a supplemental air suspension system on single and dual-rear-wheel applications. With the addition of air bags, the leaf springs were softened, allowing for more unladen suspension movement.
2. Kelderman offers a different approach to the air spring assist game with its Two-Stage kits that replace the rear shackle hanger assembly. In its place, a new assembly that houses an air spring makes the connection to the leaf spring shackle. This design allows for the initial harshness of bumps to be absorbed by the bags before being transferred to the leaf springs. The result is a very smooth ride when unloaded and a fully capable regular heavy-duty vehicle when fully loaded. This allows for easier daily use of a normally unbearable large truck’s rear suspension. Kelderman also offers link-type systems that completely replace the stock suspension components for an even smoother ride.
3. Some custom vehicles want the front-up, rear-down stance for an evening of cruising; this is not one of those vehicles. This setup benefited from the leveling abilities of a helper airbag setup.