TESTING MACHINES FOR MEASURING THE UNIFORMITY OF PASSENGER CAR TIRES
In recent years the comfort and fatigue of passengers in vehicles has become a major engineering consideration. Among the many factors involved are vibratory and auditory disturbances. Tires participate, among other elements of the vehicle, in exciting vibrations and noises. Furthermore, tires also may generate forces leading to lateral drift of the vehicle.
This recommended practice describes the design requirements of equipment for evaluating some of the characteristic excitations of passenger tires causing disturbances in vehicles. The kinds of excitations treated result from nonuniformities in the structure of the tire and have their effect when a vehicle bearing the tire travels on a smooth road.
This recommended practice also describes some broad aspects of the use of the equipment and lists precautionary measures that have arisen out of current experience.
The intention underlying these recommendations is to establish the best standardized measurement for use by the engineering community that our present state of knowledge allows.
There is a considerable body of evidence that supports the statistical relevance of data obtained from the type of equipment and the procedures described. However, the mechanical instability of the materials of a tire responding to the effects of temperature, storage conditions, and surface contamination, as well as the previous history of usage, etc., all produce variations in vibratory excitations. For these reasons the measurements of individual tires are often cloaked in a degree of uncertainty. Nevertheless, larger values of vibratory excitations are usually well identified, and statistical evaluations of the data usually serve to indicate properly the quality of production lots of tires.
Criteria of quality which might be based on measurements made under this recommended practice follow from the needs of individual engineering applications and are consequently not sufficiently general to be specified here.