Front suspension (Description): Description and operation

Description

General

The front suspension comprises two MacPherson strut dampers with coil springs, two lower suspension arms and an anti-roll bar. A front subframe is bolted to the body and provides mounting points for the lower suspension arms. Each damper has a steering arm which provides for the attachment of the track rods from the power steering rack.

The suspension is designed to allow longitudinal movement of the wheel, which allows the wheel to move rearwards and upwards in response to surface undulations. The longitudinal movement allows the springs and dampers time to react to surface changes which improves ride quality.

MacPherson Struts

The left and right hand dampers are handed but otherwise similar in construction. The front dampers are similar to the rear dampers but have slightly different damping characteristics. The damping characteristics of the front dampers also differs between model variants. The spring rates also differ between the front and rear suspension and model variants.

The damper has a forged steering arm which provides for the attachment of the track rod via a ball joint and the antiroll bar link. The damper body is fabricated from thick walled tubing and has welded brackets for attachment of the swivel hub. A smaller welded bracket provides for the attachment of the brake hose to the caliper and the ABS sensor cable.

Each damper is fitted with a coil spring. The coil spring locates in a fabricated seat and is retained in a partially compressed condition on the damper by a spring seat, top mount and nut. The top mount is fitted with three studs which locate in mating holes in the inner wing turret. The top mount is fitted with a bearing which allows the damper rod to rotate when the steering is turned.

On vehicles fitted with air conditioning, the front springs are approximately 5 mm longer. This maintains the correct ride height with respect to the additional weight of the air conditioning equipment.

A spring aid and a bump cup are fitted to the damper to prevent shock loads when the damper is fully compressed. A dust cover prevents the ingress of dirt and water to maintain the integrity of the chromium plated damper rod.

The damper functions by restricting the flow of hydraulic fluid through internal galleries within the damper. A chromium plated damper rod moves axially within the damper. As the rod moves, its movement is limited by the flow of fluid through the galleries thus providing damping of undulations in the terrain. The damper rod is sealed at its exit point from the damper body to maintain fluid within the unit and to prevent the ingress of dirt and moisture. The seal also acts as a wiper to keep the rod outer diameter clean.

Anti Roll Bar

The anti-roll bar is mounted to the upper face of the front subframe in two places. Rubber bushes fitted to the anti-roll bar are held in position by two clamps retained with bolts. The outer ends of the anti-roll bar are each connected to a link, which in turn is attached to the damper.

The links have a ball joint at each end. The link transmits suspension movements directly to the anti-roll bar. The design of the links reduces the steer effects commonly found in this type of suspension.

Lower Suspension Arms

The lower suspension arms are fabricated from steel and each arm is handed. The arms are attached at two pivot points. The forward end of the arm contains a bush and is attached to lugs on the front subframe with a bolt. A spigot on the rear mounting of the arm engages with a bush and housing assembly and is retained with a snubber washer and a nut. A ball joint is located on the outer part of the arm and is connected to the swivel hub and secured with a nut.

The two pivot bushes have a significant role in vehicle handling. The bushes control the longitudinal movement of the wheel due to braking, acceleration or surface undulations.

Front Bush The front bush is located at a specified angle to the axis of rotation of the lower suspension arm. The front bush is deflected radially and axially as the wheel moves rearwards. The angle of the bush ensures that the wheel moves directly rearward reducing the effects of longitudinal steer to a minimum.