What is ECAS (Electronically Controlled Air Suspension)?

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What is ECAS (Electronically Controlled Air Suspension)?

In the world of semi-trailers, we rely on technical innovations to carry our load. The latest innovation on the market? Electronically Controlled Air Suspension, or simply put: ECAS. But what is it and what are the benefits compared to a conventional air suspension system that only uses air valves?

Both air suspension systems have the same goal: keeping on tires on the ground at all times. Even when driving on unpaved or bumpy roads. Furthermore, there are strict height constraints for semi-trailers, which entails an unloaded truck can’t rest higher on its suspension system than a loaded vehicle. This means we need a system that’s able to adapt to the various load conditions of a trailer. Hence, an air suspension system is used on all the trailer’s axles. There’s a multitude of benefits to an air suspension system:

  • Exceptionally good driving comfort
  • Air suspension improves the ride height ensuring the trailer will always have the same height, whether fully loaded or empty
  • Less wear and tear on your trailer, making it last even longer
  • When you’re not driving, the air suspension system can be used to raise or lower the entire trailer

ECAS is the next generation of air suspension, but why is it better than the previous system? Well, the conventional system uses a levelling valve to regulate the air suspension bellows. Whenever the trailer’s height dips too low, the levelling valve opens allowing air pressure to enter the bellows. When the trailer reaches its riding hight, the valve closes. If the trailer rises too high, the valve opens again to relieve pressure. The system works perfectly fine, but it’s slow because the levelling valve slowly closes off, meaning it will take longer for the bellow to reach optimum capacity. Furthermore, when driving an uneven terrain, the valves will react to every little bump in the road and will constantly lower or raise the height of the trailer.

In comparison, ECAS works with an electronic height sensor that sends real-time data to the trailer modulator. This unit automatically calculates whether the pressure in the bellows needs to be adjusted using the solenoid valve, which ensures a more efficient suspension. The modulator also considers other factors such as the wheel speed and tipping sensors. Because this modulator operates fully electronically, and the valves are all solenoid valves which can only be fully opened or fully closed, the system reaches the correct riding hight much faster when (un)loading your trailer. With ECAS you’re sure of a safer, faster, and more efficient suspension system.

Benefits of ECAS

  • With ECAS the trailer will reach the optimal height faster as the valves open all the way to add air to the bellows as needed. In the conventional system the levelling valve slowly closes, meaning less air gets through to the bellows meaning it will take longer until the bellows are at the needed capacity to embark on the next ride
  • The system collects data, and the modulator automatically calculates the average height the trailer should have and can adjust when the trailer should be lowered or raised. This system is data-driven and is more suited to uneven roads as it will not respond to sudden dents in the road and thus will limit wasting compressed air
  • Automatically adjusts the height of the semi-trailer making the system more efficient to work with
  • ECAS provides a much safer driving experience
  • It’s possible to add additional functionalities to improve the driving experience even more! A few examples: lift axle, traction help, Optiturn, Optiload, …


*ECAS is a standard practise on all STAS moving floor trailers and tippers