CHAPTER 3 - PART 5 - CHASSIS - SUSPENSION

The main components of the suspension system are:

• Springs: may be coil springs, leaf springs or torsion bars. They support the motor vehicle's weight and deflect elastically when the wheels travel over bumps, absorbing the shocks transmitted from the road to the body;
• Shock absorbers: control spring movement, reduce suspension oscillations after travelling over bumps and help the wheels maintain contact with the carriageway. In doing so, they contribute to motor vehicle stability, steering control and ride comfort.

Types of shock absorbers:

• twin-tube shock absorbers: have two oil-filled chambers: the working chamber, in which the piston and its rod move, and the reservoir chamber, located between the working cylinder and the shock absorber's outer tube;
• gas-pressurised monotube shock absorbers: contain oil and pressurised gas (approximately 25-30 bar);
• shock absorbers used with coil springs: in many cars, the shock absorber can be integrated into a strut assembly with a coil spring, forming a structural part of the suspension. This assembly controls wheel movement and contributes to motor vehicle stability.

• Stabiliser bars (anti-roll bars): reduce the motor vehicle's body roll when cornering and help it remain more stable during changes of direction;
• Suspension arms (control arms): are pivoting components that connect the wheels to the motor vehicle's structure and allow them to move vertically while driving;
• Suspension bushes, joints and mounts: allow controlled movement of the components, reduce vibrations and noise transmitted to the body and help keep the wheel correctly positioned while driving;
• Independent suspension: in this type of suspension, each wheel can move independently of the others, helping to improve ride comfort and handling.

In some modern motor vehicles, the suspension can be electronically controlled. Adaptive suspension can adjust its damping characteristics according to road conditions, driving speed and driving style to improve stability and comfort.

The role of the suspension system:

• motor vehicle stability​: helps maintain contact between the wheels and the road surface, contributing to vehicle stability and steering control;
• handling: enables a quick and precise response to the driver's inputs;
• safety: by maintaining contact between the wheels and the carriageway, the suspension helps reduce the risk of losing control, particularly during braking, when cornering or on uneven roads;
• passenger comfort: absorbs and reduces shocks and vibrations caused by uneven road surfaces, contributing to a smoother and more comfortable ride.

The role of the suspension system in braking:

The suspension system directly influences braking effectiveness. By managing weight transfer and maintaining contact between the wheels and the road, it contributes to braking system performance and helps reduce stopping distances.

Therefore, a suspension system in good working order contributes to road safety through:

• load distribution: during braking, the front of the motor vehicle is subjected to greater loads as the load shifts towards the front axle. The suspension must control this change so that the wheels maintain their grip on the road and braking remains effective;
• maintaining contact with the road: a suspension system in good condition helps the wheels maintain contact with the carriageway, including on uneven surfaces, reducing the risk of a temporary loss of grip;
• reducing braking distance: a suspension system in good condition helps the wheels maintain contact with and grip on the road, including on uneven surfaces. By limiting oscillations and instances of the wheels losing contact with the road, it can contribute to more effective braking and reduce the distance needed to stop;
• stability during braking: when braking, the suspension helps the motor vehicle remain balanced and prevents excessive body movement. This allows the driver to maintain better steering control, particularly during sudden braking, when a loss of stability can increase the risk of an accident.