Good road behaviour of a car is dependent on a host of interacting factors rather than on just one or two good design features.
|The behaviour of a car on the road is primarily dependent on the chassis design and the chassis geometry. The track, wheelbase, wheels and tyres, suspension and springs, steering, etc. are elements that have been carefully matched to one another to provide the Saab with good roadholding and directional stability-to the benefit of road safety and comfort.|
|If the yaw rate is plotted on a graph as a function of the lateral acceleration, the curve for the theoretical ideal car will be a very narrow ellipse (shown black in the graph). The blue loop represents a competing car with front wheel drive and with acknowledged good roadholding properties.|
The Saab 900 has excellent directional stability, regardless of the speed, the road surface or the load. Since the driven and steered wheels carry most of the load, there is little risk of wheel spin, which is important when the road surface is slippery, snow-covered or difficult in other ways. Due to the design of the chassis, the Saab 900 has a "forgiving" nature - it will compensate for any minor errors the driver may make.
When travelling at moderate speeds on good roads, all cars will perform in a disciplined, well behaved manner. The car will only show its true mettle when the road conditions become more difficult. Front-wheel drive, favourable weight distribution, good suspension characteristics, rack and pinion steering, and the geometry of the steering and chassis - these are the features that have been ideally combined to make the Saab 900 so outstanding when the road and weather conditions are at their worst.
The ideal car
A car must be able to give the driver fast and accurate information in all situations. The human being is very sensitive in this respect and can immediately detect differences of one hundredth of a second.
In theory, there should be no delay between the movement of the steering wheel, the car's response to the movement and the instant when the driver can actually feel the car responding. The way in which he feels this should also be consistent and logical. The driver's hands, eyes and body should receive fast, clear and accurate information.
In technical terms, the reaction of the car to movements of the steering wheel can be described in terms of yaw rate and lateral acceleration. The driver detects the yaw rate through his eyes and the lateral acceleration through his body.
Interaction between the driver and the car
The driver receives very distinct, reliable signals at all times - through the steering wheel, the pedals and the seat. This is an important element that enables him to take the correct action in all situations.