Know Your 4×4: Chassis and Suspension

4X4 chassis suspension

Know Your 4×4: Chassis and Suspension

The Chassis

The chassis is a frame to which the vehicle’s body is mounted, the suspension and axles are fitted to the underside of the chassis, keeping the wheels in contact with the ground.

Ladder Frame Chassis

Consists of two parallel beams running the length of the vehicle, joined by cross members.

ladder frame chassis

A Monocoque

Is a unitary construction. The body, chassis, suspension etc. are all integrated. This system gives a 4×4 a comfortable ride. With a monocoque chassis, wheel articulation is reduced and the body is more rigid.

monocoque chassis

Suspension Systems

Suspension is the system of tyres, springs, shock absorbers and linkages that connect a vehicle to it’s wheels. They are designed to absorb road shocks while allowing the wheels to maintain contact with the road surface.

Independent Front Suspension (IFS)

This is a suspension system that allows wheels on the front axle to move up and down independently of one another. It is used on most Double and Single Cabs coupled to a live rear axle.

All-Round Independent Suspension

A system allowing all the wheels to move up and down independently. This reduces wheel articulation, while giving a comfortable ride, so it is often fitted to SUVs.

All-Round Live Axle

This uses ‘solid’ or ‘beam’ axles which allow opposing wheels on an axle to
operate in tandem Live axles are coupled to either a ‘coil-spring-over-shock-absorber’ combination or leaf springs and shock absorbers. Live axle suspensions are fitted to tough pick-ups and large SUVs as it offers greater wheel travel and load carrying capacity. Some passenger comfort is sacrificed.

Multi-link Solid-axle suspension

This design uses ‘coil-spring-over-shock-absorbers’. The axle is held in place using control arms, or links.

Torsion Bar

Is a spring that looks like a long metal rod. One end of the rod is attached to the
vehicle’s chassis, the other end is attached to the suspension’s control arm. When the control arm moves, the torsion bar is twisted and then returns to its original form. This is mounted to independent front suspension systems.

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