The front suspension has 2 primary purposes:
| • | Isolate the driver from irregularities in the road surface. |
| • | Define the ride and handling characteristics of the vehicle. |
The front suspension absorbs the impact of the tyres 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 vehicles 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 tyre and wheel assembly as the vehicle travels over irregular road surfaces while maintaining the tyre's horizontal relationship to the road.
This requires that the steering knuckle be suspended between a lower control arm and a strut assembly. The lower control arm attaches from the steering knuckle at the outermost point of the control arm. The attachment is through a ball and socket type joint. The innermost end of the control arm is attached to the vehicle frame through a bushing. The upper portion of the steering knuckle is attached to a strut assembly by two bolts and nuts. The strut assembly then connects to the vehicle's body by way of a support bearing and mount. The steering knuckle is allowed to travel up and down independent of the vehicle body structure and frame. A shock absorber is used in conjunction with this system in order to dampen out 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 strut unit. Valves inside the shock absorber offer resistance to oil flow and consequently inhibit rapid movement of the piston and shaft. Each end of the shock absorber is connected in such a fashion to utilise this recoil action of a spring alone. Each end of the strut unit is designed as the connection point of the suspension system to the vehicle and acts as the coil spring seat. This allows the strut assembly to utilise the dampening action to reduce the recoil of a spring alone.
The lower control arm is allowed to pivot at the vehicle frame in a vertical fashion. The ball joint allows the steering knuckle to maintain the perpendicular relationship to the road surface. The subframe is bolted to both longitudinal frame side members. The front subframe to side member attaching bolts incorporate a tapered boss near the head of the bolt on the front bolts, to assist in front subframe to body alignment during assembly while the pivots of the front control arms are rubber bushed and are attached to the subframe by bolts and nuts.
A stabiliser bar is mounted to the subframe by two brackets and insulating rubbers. The link connecting the stabiliser bar to each front suspension strut assembly has a ball joint and nut at each end. There are numerous configurations for each suspension option, depending on body type and powertrain combination. For further information regarding the identification of which suspension option is fitted to a particular vehicle, refer to Vehicle, Engine and Transmission ID and VIN Location, Derivative and Usage. For all other information regarding the suspension specification fitted to a particular vehicle, refer to Fastener Tightening Specifications.
