It’s a system designed to dampen oscillation or slow down a movement, compression or extension, of the vehicle suspension system. It is made mostly of metal parts and is hydraulic.
It consists of two coaxial (or concentric) cylinders, an external ring-shaped one and an internal one in which a piston slides with the rod anchored to the vehicle frame or vice versa.
The internal cylinder is always full of oil, the external one just partially so. The volume of oil in the two cylinders is controlled by various systems.
There are generally two valves inside the shock absorber: a compression valve and a compensation valve, respectively referred to as rebound and intake; their purpose is to connect the two coaxial cylinders and regulate the oil flow inside these two chambers as the shock absorber moves.
These two valves are very important because they regulate the flow of oil and thus allow us to create the desired damping effect.
By acting on one or the other it is possible to make the shock absorber harder or softer and so create different calibration set-ups as we shall see in a further lesson.
Shock absorbers come in a wide range of diameters and sizes, feature various types of anchoring systems and must always provide a good working match with the vehicle suspension system.