Your car’s suspension system maximises the friction between the tyres and the road surface, to provide steering stability with good handling and to ensure the comfort of the passengers. If you don’t service it regularly, you’re in for a bumpy ride.
The suspension system is designed to give you a smooth ride while maintaining excellent driving control. When your car accelerates, bumps cause forward energy to be converted into vertical energy, which then travels through the frame of your car. Without coil and leaf springs to absorb this, the vertical energy would cause your car to jump up off the road, reducing tyre friction and control. Your car would then come crashing back down onto the road with even greater force, making for a very uncomfortable and dangerous ride.
All suspension systems are different, but most include a chassis or frame, coil springs, leaf springs, dampeners including struts and shock absorbers, and anti-sway or torsion bars in various combinations.
Coil springs and leaf springs are designed to absorb up/down forces to keep tyres planted firmly on the road. Most modern cars have independent front/rear suspension. Dampeners, namely struts and shock absorbers, dissipate the energy absorbed by coil springs, so up/down motion is quickly reduced to zero. If the dampeners are in proper working order, the passengers should be unaffected by dips or bumps in the road. If shock absorbers are old or faulty, once the car starts bouncing, it continues to bounce for a long time.
Some cars also have torsion bars (anti-sway or anti-roll bars) that span the car’s frame and help level out side-to-side motions while cornering. Torsion bars are an important feature of the suspension system, particularly on high-profile vehicles (such as 4WDs) that are considered top-heavy.