Applying a force to this object deforms it. Removing the force lets it return to its original shape. This characteristic is called elasticity.
Automotive suspension systems generally use the elastic properties of metals, to provide the springing medium.
The springs are located between the frame and the axle assemblies, and are shaped to suit the application.
Leaf springs are normally semi-elliptical, and they absorb the applied force by flattening out under load.
Coil springs are formed in a spiral from a single steel rod, and absorb the force of impact by twisting.
Torsion bars are held rigid at one end, and twist around their centre as the suspension arm is deflected.
They all return to their original shape when the deflecting force is removed.
Non-metallic materials, like rubber, can provide the main springing action, but are more commonly used as stops, to limit extreme suspension movement.
The stops can also be shaped to provide an auxiliary springing function.
In light vehicle applications, air is normally used only for ride-height control.
When a vehicle strikes an uneven surface, the springs are deformed from their original shape. They return to their original position, but tend to overshoot, and set up oscillations.
This makes the vehicle bounce up and down, which makes the ride uncomfortable.
It can produce forces that make the tires bounce. And a bouncing tire won’t grip the road surface well.
Shock absorbers have a marked effect on how well tires follow a road surface. They damp the natural bounce over the road, and reduce spring oscillations.
There are different kinds of shock absorbers, but they all use a piston sliding in a cylinder filled with oil.
The dampening action occurs as a result of the piston movement, forcing the oil through valves in the piston, and at the foot of the shock absorber, which restrict oil flow.
The oil heats up from this continuous movement as the energy of motion of the suspension is transformed into heat. This heat is transferred through the body of the shock absorber to the outside air.