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The author starts with the development of the pneumatic tire since its invention by Dunlop in 1888, and proceeds to show why several different types of tire construction are now in use. The merits of the three types of tires, namely, the clincher, straight-side and quick detachable, are discussed as regards energy consumption, traction, total mileage, cost-per-tire-mile, cushioning effect, reliability, ease of applying and service. The conclusions brought out show principally the advantages of the straight-side tire. Statistics are offered to show the trend of the rim situation, and it is pointed out that it is just a question of time when the quick detachable clincher will cease to survive. It had a legitimate place during the development stage, but with the developed straight-side tires giving entire satisfaction, the author holds that there is no excuse for continuing the quick detachable clincher type.

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.

STATISTICS show clearly that, while the quantity of synthetic is increasing at a satisfactory rate, the stockpile of natural rubber is already dangerously low, with little hope of improvement very soon. Less than 10% of the natural rubber that we actually need is being imported into the country. It is necessary, therefore, that truck and bus operators learn the limitations of the synthetic tires that they will continue to get, and which will contain increasing percentages of synthetic. To aid the operators in giving these tires the care they need for maximum life and repeated retreadings, Mr. Hale gives here a short manual of dos and don'ts for the proper care of synthetic tires.

THIS paper is a non-technical review of an up-to-date survey of the lines of tires needed in all types and classes of fleet operation. To understand better how to get the best results from their operations, operators must know the proper type of tire to use. The author first describes and catalogs the principle forms of tire failures, then reviews the characteristics of the fundamental lines of tires available at the present time. Next, an attempt is made to classify the different types of fleet operation so that definite recommendations can be made as to the most appropriate tire equipment for these vehicles. The types of tire trouble most commonly encountered in each group are brought out with suggestions on how to avoid them. This part is followed by a section giving advice on the care of tires. The paper concludes with a brief survey of worthwhile facts about repairs and retreading. An appendix contains the load-inflation tables which are most widely used.

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.