Experimentally measured temperature rise in tires is used to calculate tire temperature profiles and to estimate the mechanical loss of cords and rubber. These data are used to establish the relative importance of cords and rubber in tire rolling resistance. Three types of tires are examined: a bias passenger tire, a radial light truck tire, and a radial passenger tire. It is shown that the relative contribution of cords varies from 10 to 85 percent which is much more than expected on the basis of results reported in the literature. Each set of results is resolved in the rolling resistance due to: (a) the mechanical loss in tire sidewall, and (b) the loss in the shoulder-crown area. Effects of speed and load on tire are also discussed.