Suspension & Steering

Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. more...

Suspension systems serve a dual purpose - contributing to the car's handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibrations. These goals are generally at odds, so the tuning of suspensions involves finding the right compromise. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. Design of front and rear suspension of a car is different.

Passive, Semi Active, and Active Suspensions

Traditional springs and dampers are referred to as passive suspensions. If the suspension is externally controlled then it is a semi-active or active suspension.

In the past devices such as air springs, and switchable shock absorbers, have been referred to as semi-active suspensions. The difference between semi-active and active is a bit of a grey area. Delphi currently sell shock absorbers filled with a magneto-rheological fluid, whose viscousity can be changed electromagnetically, thereby giving variable control without switching valves, which is faster, and probably cheaper and probably better. An Australian company, Kinetic, is having (as of 2005) some success with various semi-active systems, which provide adjustable roll control and damping, by using cross linked shock absorbers, and other methods. They have now been bought out by Tenneco.

Fully active suspensions use external power (typically hydraulic or pneumatic) to directly control the motion of the car. They have been around for a long time, notably Lotus developed several prototypes, and introduced them to F1, where they have been fairly effective, but have now been banned. Nissan introduced a low bandwidth active suspension in circa 1990, for the domestic market only.

Read more at Wikipedia.org