DR. BULL emphasizes the vital role that tires play in car stability, not only because they provide the final connecting link between car and ground forces, but also because they have inherent properties which are indispensable to safe and smooth steering control. Stability, however, is a relative matter, he explains, as the skill and experience of the driver enter into the problem to a very considerable degree. Although the factors in car or chassis design which affect stability are numerous and complex, this discussion deals only with that portion of the problem which relates to the behavior of tires under the different conditions to which they are subjected.
That stability is far from uniform among tires of different manufacture, and that speed has very little effect on cornering force under practically all conditions, are two of the conclusions reported from experiments made on a test machine built especially for studying the behavior of tires under a wide range of conditions. Data and charts to show the important relationships between slip angle, cornering force, load, inflation, self-aligning torque, and camber thrust are presented. Results of work on the application of driving and braking torque, and on the effect of slip angle on the power consumption of tires, also are revealed.
In conclusion, Dr. Bull stresses the point made by other workers in the field - that stability is but one of the factors in tire quality and that, although it can be increased, the gain usually is at the expense of other desirable properties.