Mechanic Glossary

Active Suspension System

An advanced suspension system that uses onboard computers and hydraulic or pneumatic actuators to dynamically adjust shock stiffness and ride height.

Active suspension replaces standard springs and shocks with computer-controlled actuators. Sensors at each wheel track body movement, vehicle speed, and steering angles in real-time. The suspension computer uses this data to adjust individual struts within milliseconds. It pumps fluid or air in to stiffen the suspension when cornering to prevent body roll, and softens it on straight highways to absorb bumps. This provides a flat, stable ride.

These systems require a lot of components, including oil pumps, valve blocks, pressure sensors, and thick hydraulic lines. Leaks are common as the components age. If a hydraulic line ruptures, the system loses pressure, causing the suspension to drop onto its bump stops, making the vehicle unsafe to drive.

Frequently Asked Questions

Passive suspension uses standard steel springs and shocks that have fixed rates. Active suspension uses sensors and actuators to change spring and shock rates continuously to match driving conditions.
Many European vehicles use a specialized synthetic mineral oil (such as Pentosin CHF 11S). Never use standard power steering fluid, as it will destroy the seals inside the expensive struts.
Yes. Because active parts are expensive to replace, many companies sell conversion kits that swap the active struts for standard coilover shocks. You will need to install bypass modules to turn off the dashboard warning lights.
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