Car suspension acts to maximize the contact and friction between the tyres and the road surface. Effective suspension enhances steering stability and improves handling as well as provides comfort to the occupants of the vehicle.

Vehicle suspension has three main functions which is to minimise the effect of bumps, to promote tyre contact with the road or surface and to provide vehicle stability. Suspension is designed to absorb the energy of the forces acting on the wheels.

Studying the dynamics of suspension, its role is to carry weight, absorb energy, dampen shock and allow the frame of the vehicle to move while the tyres follow the terrain. Vehicle dynamics covers three important principles - road isolation, road holding and cornering.

Off-Road Vehicles

Suspension systems for 4WD off-road vehicles are typically more complex and robust compared to conventional passenger vehicles. Off-road vehicles are usually heavier, with larger wheels and they are designed for operations in terrain where the vehicle is subject to much higher shock and forces than under on-road conditions.

The primary goal of a suspension modification is to raise the vehicle body and frame of the vehicle to create additional ground clearance. This also provides extra clearance for larger tyres and increases suspension travel.

­As a car hits a bump, a shaft is driven upward into the shock absorber's oil chamber. The piston inside the shock regulates how quickly the shaft moves up (compresses) and moves down (rebounds). Through the provision of correct compression and rebound the manoeuvrability of the vehicle is improved. Commonly, shock absorbers are pressurised with Nitrogen to prevent the oil from foaming and losing it's compression and rebound properties.

Springs and shock absorbers form the two fundamental parts of a suspension system.

Springs

Common spring systems are typically based on four design types:

• Coil springs - Store and release energy to absorb shock or maintain a force between two contacting surfaces.
• Leaf springs - Consist of several layers of metal ("leaves") combined together to act as a single sprung unit. 
• Torsion bars - Employ the same principles as coil and leaf springs except they act by twisting along their axis to provide spring force. One end of the torsion bar is anchored to the vehicle frame and the other end is attached to a wishbone which acts like a lever that moves perpendicular to the torsion bar.
• Air springs - Consist of a cylindrical chamber of air positioned between the wheel and the car body and use the compressive qualities of air to absorb wheel forces and vibrations.

Shock absorbers

A shock absorber controls unwanted spring motion by slowing down movement and reducing vibrations. This is achieved by converting kinetic energy into heat.

When the car wheel encounters a rut or a bump in on/off road conditions, this causes the spring to coil and uncoil. The energy of the spring is transferred to the shock absorber, down through the piston rod and into the piston. This process slows the piston movement which in turn slows the movement of the spring.

The Ultimate Suspension's proprietary "Aussie Ryder" shock absorbers are velocity-sensitive. This means that the faster the suspension moves, the more resistance the shock absorber provides. This enables shocks to adjust to road conditions and to control the unwanted motions that can occur in a moving vehicle, including bounce, sway, brake-dive and acceleration squat.

See the video below - "Suspension and how it works"