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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.