While developing an analytical model for tire power loss, it was observed that the thermal state of a tire, and thus the factors which affect this thermal state, have a large influence on predicted levels of power loss. An experimental program was conducted to determine the actual magnitude of such effects. Parameters chosen were those capable of altering the thermal state of the tire by changing the rate of heat flux from its surface. Specifically, test results are presented which include the effects of wheel material, venting, and blading, and various types of tire sidewall roughness including lettering. Among all configurations tested, power loss was found to be least for smooth sidewall tires on wide, nonbladed, and nonvented plastic wheels.