Shock Absorbers - What is Their Function

“There seems to be a lot of misconception about what a shock absorber is and what it does. Can you explain its function?”

The function of the shock absorber is to, as far as possible, keep the tyres in contact with the road surface thus ensuring safe and controlled vehicle handling. It does this by controlling the action of the spring and suspension movement. There are several types of shock absorbers but for the purposes of this article we will only be looking at telescopic, hydraulic shock absorbers as used on our 4x4’s. Some of these are plain hydraulic shock absorbers, many have gas charging (“gas shocks”) and a few have foam cell technology. They can also be either Mono-tube or Twin-tube in design.

The word “shock absorber” is a bit of a misnomer. It is actually a damper or dampener. The shock absorber dampens the spring and suspension movement by restricting the flow of hydraulic fluid inside the shock absorber when it is compressed or extended through the suspension movement. The hydraulic fluid flows through restrictive orifices and valves within the working piston and the foot valve. It is this restriction that generates the damping resistance. This varying resistance gives the shock absorber its dampening ability. The shock absorber therefore does not absorb road shock but rather the energy transferred into the spring by the road irregularities.

Scientifically, the shock absorber converts the energy from the vehicle’s springs into heat inside the shock absorber oil by means of this restrictive flow dampening action. This heat is then dissipated into the atmosphere through the outer surface of the shock absorber body. One can easily confirm this by touching your shock absorbers after a couple of km’s down a corrugated road.

As a rule, shock absorbers do not determine the ride height of the vehicle, and one cannot therefore raise the ride height of a vehicle by merely fitting longer shocks. Shocks also do not support the weight of the vehicle. It is the function of the spring to hold the body and chassis of the vehicle above the wheels and axles at a predetermined ride height, enable the vehicle to carry load and most importantly, to absorb the road irregularities.

The suspension engineer can vary the amount of dampening action of a particular shock absorber by the design of the piston and the valve coding. The stiffer the springs and the more load you carry, the more control you are going to need from your shock absorbers to ensure a safe and controlled ride. Merely fitting stiffer springs without matching the shock absorbers is therefore not a good idea. Conversely, fitting heavy duty shock absorbers to standard springs could lead to over damping or too much control. This is as dangerous and could induce a very uncomfortable ride.

Adjustable shock absorbers are an ideal solution in an ideal world. Most are not easily adjustable once fitted though. There are shock absorbers that can be adjustable on the go from within the vehicle cabin but they are pretty scarce and very costly. The trick is to accurately determine your predominant requirement for your suspension and tailor your upgrade accordingly.