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.