In order for the rear wheel to move upwards over a bump in the road, the swinging arm must compress the rear suspension unit or shock absorber. In this way it allows the rear wheel to react to imperfections in the road by moving upwards (when riding over a bump) or downwards (when riding over a hole) therefore isolating the rest of the motorcycle from that motion.
Like the front suspension, the rear shock absorber consists of a coil spring that offers a controlled resistance to the swinging arm moving upwards. The speed at which the coil spring compresses or extends is further controlled by simultaneously squeezing oil through tiny holes during these movements. This is called damping and can be likened to a damper on the rear hatch-back door of an SUV to stop it falling shut as you load the car. The oil flow through the damping system can sometimes be adjusted.
Why upgrade your rear suspension?
When manufacturers choose a suspension for their new motorcycle they must make a compromise between cost and quality. Normally, the higher the cost of the motorcycle, the higher the quality of the components.
Regardless of cost, most standard suspension systems can be improved upon with finer tolerances of engineering, better quality materials and more options for adjustability that enable you to alter the suspension to suit your weight or the way and places you ride.
Upgrading suspension is the single most effective way to improve the comfort, stability, safety and performance of your motorcycle or scooter.