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Whenever we hear the term “air suspension,” it often comes with a fixed impression—unmatched comfort. While it’s true that many executive sedans are equipped with air suspension systems, semi-trucks are also loyal users of this suspension.
So, what exactly is air suspension? And what are its advantages and drawbacks? If you’re curious, keep reading.
What is Air Suspension?
Car suspension system consists of many components, with springs and shock absorbers playing the main role in reducing vibrations from the road to the vehicle body. This helps keep the ride smooth and comfortable.
In other words, if you replace the traditional coil springs with air bags (air-filled bladders), you basically have an air suspension system. Therefore, air suspension is essentially an air spring system.
Vehicles Equipped with Air Suspension
Some well-known vehicles equipped with air suspension include:
- Bentley Continental GT/ Porsche Panamera
- BMW 7 Series
- Mercedes S-Class
- Lexus LS
- Rolls-Royce
These vehicles are luxury or executive sedans and tend to be heavy. Air suspension helps provide superior comfort and handling for such cars.
Which Suspension Types Can Use Air Suspension?
There are many types of suspension systems, and in principle, air suspension can be integrated with all of them. However, due to the characteristics of air suspension, currently only independent suspension systems are used with air springs in passenger vehicles.
In other words, air suspension is typically found on double wishbone and multi-link setups. These suspension types share common traits—they take up more space, add weight, and come with higher costs.
Components of Air Suspension?
As mentioned earlier, air suspension is basically found only on multi-link and double wishbone suspensions. Therefore, the structure of air suspension largely shares components with these systems.
The key parts include:
- Suspension arms
- Stabilizer bar
- Ball joints
- Shock absorbers
- Springs
- Air compressor
- Air tank
- Control module
The main differences between air suspension and conventional multi-link or double wishbone lie in the springs and shock absorbers, as well as the addition of the air compressor, air tank, and control module.
Next, we will focus on the air springs and shock absorbers.
How Does an Air Spring Work?
An air spring works by pumping air into a rubber bladder, using the compressibility of air to fulfill the basic function of a spring. The rubber bladder is often reinforced with woven fibers to improve durability.
When the control module detects the need for more air or higher pressure to stiffen the spring, it sends a signal to the air compressor or air tank to inflate the airbag. Conversely, when less air is needed, excess air is released either into the atmosphere or back into the air tank through another valve line on the air spring.
By inflating and deflating the air spring, both the spring rate and the vehicle’s ride height can be adjusted in real time. In contrast, traditional coil springs have fixed parameters and cannot be adjusted.
What is a Shock Absorber in Air Suspension?
Basically, the shock absorber used in an air suspension system isn’t all that different from a conventional shock absorber—they’re both dampers designed to control vibration. However, vehicles equipped with air springs almost always come with electronic shock absorbers as well. This is because when the spring height or stiffness changes, the damping characteristics need to adjust accordingly. Without this coordination, the suspension components can work against each other, leading to a rough or unstable ride.
Thanks to the vehicle’s onboard computer and a network of sensors, the air springs and dampers are continuously adjusted together. This seamless coordination is what gives air suspension its famously smooth, “magic carpet” ride quality. Modern systems can detect and adapt to changes in suspension settings in as little as 100 milliseconds.
Electronic shock absorbers come in various types depending on their control methods, but that’s beyond the scope of this discussion. Generally, they use a controller to open and close valves inside the shock chamber to adjust damping levels on the fly.
In short, electronic shock absorbers usually go hand in hand with air suspension systems, offering a combination of superior comfort—at a higher cost.
Advanced Adaptive Control Technology
Besides the two key components mentioned earlier, the computer control module is actually the core of the air suspension system. Fine-tuning this module is a specialized task.
In addition, electronically adjustable anti-roll bars are also an essential part of the system. Their inclusion allows for more precise body control, enabling the vehicle to seamlessly switch between extreme comfort and sporty handling. A well-tuned air suspension can even provide a distinctly different driving experience.
In recent years, some manufacturers have integrated camera technology to scan the road ahead in advance, allowing the computer to adjust the air suspension proactively. This enhances ride comfort and safety by enabling the suspension to react ahead of time.
Air Suspension in Electric Vehicles
Many electric vehicles have also adopted air suspension, mainly due to the heavy weight of their batteries, which traditional coil springs struggle to manage effectively in terms of vehicle dynamics.
Since air suspension systems involve numerous sensors, controllers, and complex components, their cost is quite high. Therefore, air suspension is mostly found on high-end models from luxury brands.
Advantages of Air Suspension
1. Excellent Comfort
For traditional coil springs, improving comfort usually means changing the spring’s material, wire diameter, or coil pitch. But making springs too soft to increase comfort can lead to durability issues. However, with air springs, these concerns are largely avoided because air pressure can be adjusted dynamically.
2. Adjustable Ride Height
Air suspension allows for ride height adjustment, which is not possible with fixed coil springs.
3. Comfort Without Sacrificing Handling
By adjusting air pressure (P), volume (V), and Area (A), air suspension can create variable characteristics. This means the suspension can soften over bumpy roads for comfort, yet quickly firm up during high-speed maneuvers like lane changes. The spring doesn’t become too soft, preventing unsettling feelings for the driver—allowing the vehicle to perform well in both comfort and handling.
4. Good Load Carrying Capacity
Unlike coil springs that may deform over time under heavy loads, air springs simply adjust air pressure to handle different weights. This is why semi-trucks commonly use air springs.
Disadvantages of Air Suspension
1. High Design Costs
Air springs usually need to be integrated with electronic shock absorbers, which involve complex vehicle dynamics calculations, making the overall system costly to design.
2. High Maintenance Costs
Air suspension systems in passenger cars typically last around 80,000 miles. After that, there’s a high chance of noise or failure requiring replacement. In contrast, coil springs rarely fail, and if they do, they are cheaper and easier to replace individually—advantages that air springs lack.
3. Higher Alignment Costs
Vehicles with air suspension have more complex electronic components, making wheel alignment more difficult and costly.
4. Limited Performance
Air suspension mainly focuses on maintaining ride balance. At the vehicle’s getting close to limits, it keeps the body stable, but compared to the more direct and predictable feedback of coil springs, drivers may find it harder to sense the car’s true state. This can make controlling the vehicle in extreme situations more challenging.
References
- T.G.Q R&D
- T.G.Q Sales
