SUSPENSION | SHOCKS
Suspension systems for vehicles have progressed in leaps and bounds since the invention of the motor car. Vehicle suspensions can be broadly classified into two sub-groups namely dependent and independent suspension systems. Suspension is the term given to a system of springs, shock absorbers and suspension linkages and steering components that connects a vehicle chassis to its wheels.
A dependent suspension normally has a beam or driven live axle (a solid axle that uses the driveshafts to transmit power), that holds the wheels of the vehicle parallel to each other and perpendicular to the axle. When the camber of one wheel changes, the camber of the opposite wheel changes in the same way, by convention on one side this is a positive change in camber and on the other side. The solid axle is driven by the means of a centre differential that drives side shafts within the axle housing.
An independent suspension allows wheels to rise and fall on their own without affecting the opposite wheel therefore being isolated from movement on the other side. Suspensions with other devices, such as sway bars that link the wheels in some way are still classed as independent suspensions. This suspension set up includes the centre diff which is usually fastened to the chassis and has drive shafts coupled with constant velocity joints that drive the wheels.
It is important for the suspension to keep the wheels of a motor vehicle in contact with the different and ever changing road surfaces as much as possible, because all the forces acting on the vehicle do so through the tyres of the vehicle.
Vehicles which carry heavy loads will often have heavier springs to compensate for the additional weight. Heavier springs are also used in performance applications where the loading conditions experienced are more extreme. Riding in an empty truck used for carrying loads can be uncomfortable for passengers because of its high spring rate relative to the weight of the vehicles mass.
Springs that are too hard or too soft cause the suspension to become ineffective because they fail to properly isolate the vehicle from the road. Vehicles that commonly experience suspension loads heavier than normal have heavy or hard springs with a spring rate close to the upper limit for that vehicle's weight.
A race car would also be described as having heavy springs and stiff shocks and would also be uncomfortably bumpy. However, even though we say they both have heavy springs, the actual spring rates for a truck and a race cart are very different. Vehicles with worn out or damaged springs ride lower to the ground which reduces the overall amount of compression available to the suspension and increases the amount of body lean. Performance vehicles can sometimes have spring rate requirements other than vehicle weight and load.
An automotive suspension strut is a structural component designed to resist longitudinal compression which generally incorporates a shock absorber as a damper. The struts provide outwards facing support in their lengthwise direction, which can be used to keep two other components separate. The most common form of strut in an automobile is the MacPherson strut.
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