Air suspension and how it works

Air Suspension Basics

The basic air suspension system comprises a compressor, storage tank, air springs, lines and fittings, and a control mechanism. When integrated, these components constitute the vehicles' primary suspension system, and allow for adjustable ride height by changing air pressure, which alters the air spring load and rate characteristics.

For our purposes, the most important consideration is adjustable ride height. Contemporary sport truck, custom, and street rod styling mandates a lowered stance, while discriminating enthusiasts demand technical sophistication. Our air suspension systems satisfy both requirements. Another important consideration in this conversion is proper shock absorber fitment. Easy Street systems include all the bracketry need to relocate the shock absorber to the optimum position. As air suspensions become more popular, there is an increasing emphasis on radical rear suspension modifications, including frame "notching" and the employment of 3 and 4 link trailing arm axle locating systems, such as in our 88-98 Chevy/GMC rear kit (75610). Easy Street systems are designed to allow for maximum suspension travel "out of the box". In addition, we offer optional bolt-on and weld-on C-notches, dropped spindle and disc brake conversion kits, and remote control. The following air suspension FAQ and component descriptions provide information relative to basic air suspension design and performance. 

How does an air spring work?

An air spring employs a flexible membrane to capture compressed air. The “spring” is the air, and an air spring takes advantage of the physical properties of air that allow it to be compressed. As the bag is compressed, the air pressure in the bag increases, forcing the bag to seek a return to its static height, or to “rebound”, similar to a steel spring.

How is an air spring rated?

The spring load and rate characteristics of an air spring are determined by its physical configuration, and manipulated by air pressure.
Spring load is the amount of weight required to compress a spring to a given height, at a given pressure.

Load is expressed in lbs. Spring rate is the amount of weight required to compress the spring one inch, and is expressed in lbs./in. Therefore, the spring load determines how much the spring can support at a given height, and the spring rate determines how much the spring will compress as the loading increases.


What do the terms convoluted, rolling lobe, and tapered sleeve mean?

Convoluted refers to an air spring constructed with one, two, or more convolutions, which are defined by the end plates and equally-spaced dividing rings which have a lesser diameter than the rubber membrane. This construction forms a bellows, or “donut” shape. Rolling lobe and tapered sleeve air springs are cylindrical in construction. Typically sleeves have a lower rate curve than bellows, which provides a more comfortable ride when carrying for lighter loads.


How durable are air springs?

Air springs are extremely durable and will last for years, if installed properly and in an appropriate environment. Air springs fail as a function of abrasion (contact with suspension and frame components), operation under extreme over or under-inflation conditions, or gross misalignment of the air spring.

Generally, a minimum of one inch of clearance between the bellows and any other structure, when the air springs are fully inflated, is necessary. Air springs should never be subjected to prolonged use at maximum pressure, and a minimum of approximately 20 psi is required to prevent internal chafing of the air spring.
A physical stop, such as a jounce bumper, is necessary to prevent the bag and/or suspension from bottoming out, in the unlikely event of a line or bag failure.

How is an air suspension system typically configured?


An air suspension system starts with an onboard air compressor and a reserve tank. The onboard compressor is necessary to supply the compressed air, and the storage tank stores the volume of air that is required to inflate the springs.
From the storage tank, air is routed to solenoid valves, and then to the air springs, by distribution lines. Available in 1 /4", 3 /8", and even 1 /2" OD’s, flexible thermoplastic tubing is the material of choice.
The most common fittings are push-to-connect (PTC). PTC fittings are reusable, although the tubing should be trimmed back occasionally so as to present a fresh surface for sealing.


What determines the flow rate of a system?

The flow capacity of a given air suspension component is called the Cv factor. Cv (“see-sub-vee”) is a coefficient based on the number of gallons per minute of water, which could pass through the part with a one psi pressure differential between the inlet and cylinder ports. In a pneumatic system, the component that has the lowest Cv determines the overall flow capacity of the system. Increasing airline size beyond the flow capacity of the other components has no net effect. Airline size is a limiting factor ONLY when it represents the smallest orifice in the system.


What is a solenoid valve?

A solenoid valve is an electrically actuated valve. Available as individual units, or mounted as a group to a base, solenoids offer high flow rates, quiet reliable operation, and a number of plumbing alternatives. Quality solenoids are manufactured from brass or hard-anodized aluminum (extruded aluminum bodies degrade in the harsh under-car environment), are rebuildable, and usually advertised as “bubble-tight”.


Is it possible to combine air springs suspension with other lowering components?

Air springs are physically compatible with dropped spindles, and are commonly used in conjunction with dropped spindles. By definition, air springs are a direct replacement for coils. Most air suspension manufacturers design their systems to ride at a height that is consistent with the OEM spring height.... therefore, when driving, the vehicle assumes a typical “dropped spindle” attitude. However, air suspensions take advantage of the fact that you can reduce height, beyond that offered by the spindle, as a function of deflating the air spring, when you are posing.

Which brings up a very important point…. although air springs allow for the vehicle to be lowered, they are not intended for lowering the vehicle on-the-fly, or for operating the vehicle in an attitude other than that which is required to maintain proper alignment when the vehicle is in motion.


Is alignment different with an air suspension?

For the purposes of alignment, an air spring should be treated like any other spring: establish ride height (driving height) and align the vehicle at that point. Yes, the alignment changes as the suspension moves through its travel, but this is true of any suspension. Alignment problems with air suspensions are usually a result of driving the vehicle at other than alignment (driving height) pressure.

Identification

1. As versatile and convenient as cars are, it's easy to overlook the small built-in comforts they provide, such as smooth riding. If it weren't for suspension systems, our travels would definitely be a bit more bumpy. Air bag suspension is an improvement over the traditional systems; however, the basic design for air suspension merely replaces the parts used in the older design. A traditional suspension system involves steel springs and shock absorbers. The mechanism itself is made up of a coil, or leaf spring, that contains a piston. As the pistons moves up and down, gas or liquid contained in the chamber works to buffer the impact of the piston. This is the shock absorber mechanism at work. The spring and piston move together in each wheel position to absorb the shock whenever the car rolls over a bump. Since the coil springs are designed to resist being compressed, they further enhance the effect of the shock absorber. Air bag suspension takes this enhanced effect a couple steps further by using air bags in the place of the spring-piston setup.

Function

2. Instead of the metal spring mechanism, strong rubber bags act as air containers. The bags are then connected to an air compressor and an air reservoir. The compressor does the job of inflating and deflating the bags, which is how the car gets raised and lowered. The resulting effects are a smoother ride and versatility in performance. These systems come with a control unit that's located inside the car to give the driver complete control over the system. As this set-up is just a modification of a traditional system, changing how your car performs is just a matter of purchasing a kit. Air bag suspension kits can run anywhere from $400 to $1,000, depending on how sophisticated the set-up is. The more complex systems enable the driver to adjust for different road conditions or for city versus highway driving.

Low Rider Designs

3. Air bag suspension systems can be installed in passenger cars, semi-trailers and buses. Within the last decade they've become popular within the custom automobile culture of street rods, trucks, cars and motorcycles. These systems are more complex and feature-rich, allowing for immediate adjustments to the level or height of the car. Known as "low riders," the suspension system is much more powerful using small electric or engine-driven air compressors. The control unit enables the driver to boost up any wheel of the car at any time to the point where the entire vehicle can be "rocked" at will. Typically, these cars are using a hydraulic suspension system wherein a bladder is filled with fluid by a compressor. This device is called an hydraulic actuator. The actuator is designed to brace the wheels against the ground so the force of the fluid into the bladder will lift the car.