 An integral part of Saab's chassis engineering philosophy is that it should not only give the driver complete control over the car, but also act as a responsive medium, supplying constant feedback on the car's reactions.
Moreover, the Saab 900 has a forgiving nature and provides the driver with ample margins for correcting any minor errors, instead of amplifying them.
The interaction between the driver and the car can be illustrated by what happens when he turns the steering wheel. The movements of the car can then be described by the concepts of yaw and lateral acceleration. The yaw rate is a measure of how quickly the car changes course. This is recorded by the driver's eyes. The lateral acceleration is a measure of the forces acting transversely on the car, i.e. how it moves sideways.The driver detects this by the side pressure applied by the seat to his hack. The seat, in turn, receives information from the tyres, through the chassis and the body. | | Computerised calculations and advanced measuring equipment designed by Saab-Scania have been used to optimise the chassis design. Conventional optical measuring equipment was not considered to be accurate enough to meet the high standards set by our designers |
If the car should skid, the yaw rate will increase and the driver will detect this with his eyes. At the same time, the lateral acceleration will decrease, since the tyres no longer grip the road and no lateral forces will therefore act on the car body. The driver will detect this with his body. The human being is extremely receptive to changes in both these phenomena. The driver will even react to very small variations and will make corrections as necessary with the steering wheel. So it is vitally important for this information to be clear and correct. In the Saab 900, all such "signal transmitters" are carefully matched in the various design features of the car, to provide the driver with correct information. The combination of optimum chassis geometry and exact interplay between the driver and the car has resulted in good roadholding and good road behaviour. The chassis is designed to provide maximum ride and driving comfort at all speeds. For optimum comfort, the chassis must attenuate vibrations of different frequencies and eliminate the fatiguing swaying and pitching of occupants' bodies. None of this is usually apparent on a short trip or a test drive. But after a longer journey in a car that does not conform to these criteria for comfort, the passengers and driver will feel tired, stiff and uncomfortable. On the Saab 900 much work has therefore been devoted to combining good roadholding characteristics with a high standard of driver and passenger comfort. This has been achieved by technical features such as the light, rigid rear axle, soft springs, suitably matched shock absorbers, well proportioned rubber bushes and a Panhard rod that effectively counteracts the rolling tendencies of the body. This design reduces the undesirable side movements and the fatiguing "swaying" motion, i.e. the tiring and unfortunately common sideways movement that causes the occupants' heads to sway from side to side. The rigid rear axle also eliminates undesirable steering effects, and the soft bushes damp out the vibrations. |
