The rear suspension has two primary purposes:
| • | Isolate the driver from irregularities in the road surface. |
| • | Define the ride and handling characteristics of the vehicle. |
The rear suspension absorbs the impact of the tires travelling over irregular road surfaces and dissipates this energy throughout the suspension system. This process isolates the vehicle occupants from the road surface. The rate at which the suspension dissipates the energy and the amount of energy that is absorbed is how the suspension defines the vehicle's ride characteristics. Ride characteristics are designed into the suspension system and are not adjustable. The ride characteristics are mentioned in this description in order to aid in the understanding of the functions of the suspension system. The suspension system must allow for the vertical movement of the tire and wheel assembly as the vehicle travels over irregular road surfaces while maintaining the tire's relationship to the road.
On front-wheel drive vehicles, the hubs are suspended between a torsion beam type rear axle. The front of the rear axle attaches to the vehicle body with semi-rigid bushings. Coil-over-shock type coil springs and shock absorbers connect to the rear axle and to the vehicle body. The rear axle moves up and down independent of the vehicle body structure. The rear suspension has a stabilizer shaft. The stabilizer shaft is connected to the rear axle.
On four-wheel drive vehicles, the knuckle is suspended between the upper control arm and the lower control arm. The inner end of the upper control arm attaches to the crossmember with a semi-rigid bushing. The forward end of the lower control arm attaches to the vehicle body with a semi-rigid bushing and a bracket. The rearward end of the lower control arm attaches to the crossmember with a semi-rigid bushing. Coil-over-shock type coil springs and shock absorbers connect to the lower control arm and to the vehicle body. The knuckle moves up and down independent of the vehicle body structure. The rear suspension has a stabilizer shaft. The stabilizer shaft connects between the left lower control arm and the right lower control arm through the stabilizer shaft links. Insulators and clamps retain the stabilizer shaft to the crossmember.
The up and down motion of the tire and wheel assembly as the vehicle travels over bumps is absorbed predominantly by the coil spring. This spring is retained under tension over the shock absorber. The shock absorber dampens the oscillations of the coil spring. A shock absorber is a basic hydraulic cylinder. The shock absorber is filled with oil and has a moveable shaft that connects to a piston inside the shock absorber. Valves inside the shock absorber offer resistance to oil flow and consequently inhibit rapid movement of the piston and shaft. This allows the shock absorber to utilize the dampening action to reduce the recoil of a spring alone.
The stabilizer shaft controls the amount of independent movement of the suspension when the vehicle turns. Limiting the independent movement defines the vehicles handling characteristics in turns.
