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Internal heat transfer through the tire cavity from the tire to the rim is strongly influenced by the speed distribution of the cavity air. For lack of any experimental data, exploratory tests with a hot-wire anemometer were performed on a radial tire operated at various loads, speeds, and inflation pressures. The measurement technique is described, and some results are presented. Cavity air flow is governed by the peristaltic action of the footprint region; however, it is strongly modified by secondary flows. The general speed distribution is very stable, with a peak at the leading edge of the footprint and a near-zero minimum at the tire top. Peak speeds of about 30% of the tire road speed were measured. These high speeds together with the augmenting effects of secondary flows may produce internal heat transfer coefficients well comparable with those at the outer surface.

This review primarily covers scrap tire disposal processes used, or suggested for use, in the U.S.A. Sufficient statistical data are presented to define the magnitude of the scrap tire disposal problem. The constraints of an ideal solution are presented as a basis for a critical review of current and proposed scrap tire disposal procedures. Our conclusion is that no one scrap tire disposal procedure is so outstanding as to be used exclusively to handle the problem. Geographic location and economics will dictate which scrap tire disposal procedure will be used.

The increasing use of brake retarders in highway opera­tion has produced an interest in the effect of these retarders on tires. It was found that more dynamic slip and tire wear was produced on the retarder axle than with drum brakes on a given braking route, but the loss in wear during the re­tarding cycle was offset by a reduction in use of brakes on other axles. Temperature buildup in tire beads indicated that repeat­ing braking cycles with drum brakes could produce tempera­tures damaging to tire components. The use of brake retarders eliminated this problem. The characteristics of brake retarders appear more fav­orable to tire durability than drum type brakes.

The increased size and capabilities of earthmoving equipment in recent years has resulted in new tire development to keep pace with the durability demanded by high speeds, heavy loading, and extreme terrain conditions. This paper discusses performance, design, maintenance, and economics of single and dual tires, and reports the results of extensive testing to determine the advantages of each type.

The relatively new wide base tire has a number of distinct advantages: over duals. One of these, improved ride, is discussed. Data taken under static conditions shows the spring rate for the wide base tire to be substantially less than for duals under fully loaded conditions, with less difference appearing under lightly loaded conditions. This, it is believed, partly explains the tire behavior as it relates to impact absorption and bounce under dynamic loaded conditions, wherein an exaggerated bump condition is introduced. Over rough concrete, also, the data shows greater impact absorption for the wide base tires than for duals.

An infrared line scanning system has been used to measure surface temperatures of automobile tires under operating conditions. A designed experiment was employed to demonstrate statistically the individual and interaction effects on tire temperature profiles of changes in tire speed, inflation pressure, and wheel load. These effects are different at different radial positions on a given tire and are quite dependent on tire construction, as illustrated by application to bias, belted-bias, and radial tires of comparable sizes.

United States heavy duty radiall truck tire usage has grown to about the same level as bias tire usage. Tubeless construction, low aspect ratio size and retread usages have increased along with the trend to radial construction. Future usage trends are expected to include tires for further fuel economy improvements, lighter weight tires, and tires to help increase vehicle efficiency in areas such as greater trailer volume and better braking life.