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THE author compares tread-wear of front and rear tires. Considering wear of rear tires as normal wear he analyses the abnormal wear observed on front tires and traces it to its causes, which are found to be camber, toe-in and imperfect geometrical layout of steering-arms and linkages. A theory of the scuffing action is developed. It is due partly to various rolling diameters at different parts of the tire tread and partly to the setting of the two front wheels so they tend to roll in slightly different directions. Reducing the camber angle to ¾ deg. and the toe-in to 1/16 in., reduces both these errors and results in longer tire-wear. No definite theory for camber is found. Toe-in depends on camber, counteracting the tendency of cambered wheels to diverge. A method is described for testing accuracy of rolling action by means of paper on a greased floor. Service stations must be put in a position to test and correct toe-in and camber.

LENGTHY consideration is given to tire overloading, with the understanding that overloading as referred to in tire failures is quite different from the application of the term overload to structural materials which collapse under a reasonably well-defined excess of load. While this paper deals primarily with overloading, there are so many other aspects relating to the use of truck-bus tires affecting the industry that a discussion is included of various other phases of the tire business intended to be instructive along the line of longer life and greater freedom from trouble. The increasing varieties of service in which motor-vehicles are being placed demand different types and characteristics of tires, which are outlined. Then there is a discussion of the relative merits of the balloon type versus high-pressure-type tires.