A vehicle’s suspension system is designed to absorb variations in the height of roads and other surfaces, to give passengers a more comfortable ride.

A good suspension system must balance the stability of a vehicle, particularly when cornering, with comfort. Too soft, and a vehicle will ‘wallow’; too hard and the passengers will suffer an uncomfortable ride.

Springs allow a vehicle’s wheels to drop or retract as they travel over rough surfaces. On their own, however, springs would introduce further discomfort, since they tend to keep bouncing. To take care of this, cars also have ‘shock absorbers’, which are hydraulic tubes designed to dampen the natural bounce of springs. The combination of the two can lead to a smooth ride.

Types of spring

• Leaf springs are long, narrow, curved metal plates attached to the underneath of vehicles. One end of them is fixed to the vehicle’s body. The other attaches to moving brackets, or shackles. U-bolts attach the leaf springs to the axles. The tension of the curved metal acts to absorb bumps in the road.

• Coil springs look like the traditional idea of curly springs. They often sit on suspension arms, rather than on the axles.

• Torsion bars attach to wheel suspension arms. Bumps in the road push up on the suspension arms, causing the attached torsion bars to twist out of their natural alignment. This provides the spring effect.

Independent vs non-independent suspension

Non-independent suspension is often found on rear wheel drive cars, as well as trucks and many four wheel drive vehicles. In this form of suspension, opposite wheels are connected by a single axle. As a result, a bump on one wheel affects the wheel at the other end of the axle. Stability and problems with traction can be the result. On the other hand, these arrangements are very sturdy, suitable for vehicles that carry heavier loads.

Independent suspension, as its name suggests, means that each wheel is mounted on its own suspension system. A bump on one wheel has no effect on the others.

Suspension arm bushes are more susceptible to wear, but all parts of a car’s suspension system need monitoring and repair over time.