Difference between revisions of "NG 900/9-3 Suspension and Steering"
Latest revision as of 07:24, 29 July 2010
The NG900 has independent front suspension incorporating MacPherson struts, which are fitted between the steering swivel members and the body and are therefore direct-acting on the wheels. Besides being of compact, robust and reliable design, MacPherson strut suspension also provides good isolation from road noise. The long stroke of the strut makes for excellent roadholding and a comfortable ride. The spring and damper act in the ratio of 1:1 to the wheel.
Front Dampers and Springs
As stated above the front suspension on the NG900 utilises MacPherson struts. This is a suspension system that consists of a combination coil spring and damper in one compact unit at each wheel. With this "independent" suspension design, road shocks at one wheel are not transferred to the opposite wheel. MacPherson struts use fewer parts, meaning a reduction on weight and fewer elements that could wear out. The strut consists of a coil spring and interior damper with welded on spring cup, steering arm mount and steering swivel member. The steering swivel member is the main component in the wheel bearing assembly and consists of a bearing housing, which is integrated with the strut, and a ball joint mounting.
The front springs are of the cylindrical compression type with the top and bottom turns of the coil springs narrower than the other turns, providing greater deflection in a given working space. They are fitted with rubber supports at the top. The top spring support also acts as a compression stop for the spring and is held in place by the tension of the partially compressed spring. The stop for the spring on extension is incorporated in the damper.
The front dampers are of the gas-filled, twin-tube type. The space between the tubes serves as an expansion chamber. The damper is not an integral part of the MacPherson strut and can be replaced separately. The piston rod is protected against dirt and moisture by a gaiter to ensure a long service life. The compression stop and the protective gaiter form a single unit.
Front Suspension Arms
One end of each suspension arm (1) is attached to the subframe via a rubber bush and the other end to the steering swivel member via a ball joint. A support arm (2), secured to the rear of the subframe via a rubber bush, braces the suspension arm longitudinally. The anti roll bar (3) is attached to either the suspension arm or the support arm depending on the year of the car. This change was put in place in 1995. Cars from VIN serial numbers S2012272 and S70414773 onwards have the anti-roll bar mounted on the suspension arm. Earlier models have the anti-roll bar mounted on the support arm. There is a kit available from Saab to upgrade the earlier models if desired.
The track rods are screwed to the middle of the steering gear via rubber bushes. The track-rod ends are secured to the track rods on both sides by means of an adjustment screw with both left-hand and right-hand threads which is used for toe-in adjustment. Each track-rod end is secured to the steering arm of the steering swivel member by means of a self-locking nut. The track-rod ends cannot be dismantled but they are self-adjusting to compensate for moderate wear.
Steering column assembly
The steering column assembly is bolted to the bulkhead. The steering column shaft is mounted in two needle bearings suspended in rubber mountings in the steering column assembly. A jointed intermediate shaft connects the steering column to the power-assisted steering gear. For reasons of safety the steering column assembly incorporates a collapsible steel cage, a telescopic steering column shaft and an intermediate shaft with a deformation zone designed to crumple progressively in the event of a head-on collision. In addition, the joint configuration is such that the shaft will be directed away from the driver in a collision. Adjustment of the position of the steering wheel spokes is achieved by adjusting the toe-in on both sides of the car.
The rear suspension consists of a semi-rigid trailing rear axle. Since the car has front-wheel drive, an extremely light and simple rear-axle construction can be used, which ensures that unsprung weight is kept to a minimum. The rear axle consists of two spring links connected by an extruded section acting as a torsion bar. There are two anti-roll bars, one outer bar and one inner bar which is inside the axle. Both anti-roll bars have a diameter of 15 mm.
Dampers and Springs
The rear springs are miniblock helical compression springs and are provided with spring supports at the top and bottom. The top supports are made of polyurethane and the bottom ones of rubber. The top spring support also acts as a bump stop. The spring supports are held in place by the tension of the partially compressed spring. The stop for the spring on extension is incorporated in the damper. The rear dampers are of the double-acting, twin-tube, gas- filled type - the gas pressure is used to maintain pressure on the damper fluid. This reduces the foaming tendencies of the fluid and also the formation of air bubbles that can result in noisy operation of the damper.