Saturday, 9 June 2012


Shock Absorbers

The function and operation of shock absorbers are widely misunderstood. Here we present the bare facts on shocks and your many options in shock absorbers.

The first lesson to be learnt about shocks absorbers is that their name is deceiving, for shock absorbers do not absorb shocks - or at least that is not their primary role. Shock absorbers are devices that resist movement and their main function is to control the movement of the car’s springs and also reduce body roll.

SHOCKS IN ACTION
When a tyre hits a bump in the road surface, the wheel and suspension moves upwards, causing the spring to compress. The spring absorbs the energy of the impact and then releases this energy by expanding.

This movement of the suspension is necessary to allow the tyre to pass over the bump without causing the body of the car to rise the same distance. However, further expansion and compression of the spring after the impact is unwanted and this is what a shock absorber is designed to prevent.

Shock absorbers, like springs, are generally mounted between the axle and the car body. When a spring expands and compresses, so does the shock absorber. The shock resists this movement by controlling the flow of oil inside the shock through a number of control valves.

How a Shock Absorber Works
With each extension and compression of the shock, known as a ‘stroke’, a piston moves up and down inside the shock and oil flows between the inner and outer chambers of the shock, known respectively as the ‘pressure cylinder’ and ‘reservoir’. The oil must pass through tiny valves which open and shut depending on the direction of the flow. The valves are precisely engineered to provide a measured resistance to the oil flow. The spring-loaded valve only opens to allow oil to pass through when enough force is supplied. This force is generated by the speed at which the shock is extending and contracting. As the stroking speed of the shock increases, more stages of the valving come into play to control the flow of the oil.

Thus the shock is sensitive to the amount and speed of suspension movement and is designed to supply precisely the amount of resistance required at any time to ensure that the suspension’s spring remains in control, performing its intended role.

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