The airflow direction, velocity, and turbulence level were measured around the left front tire of a passenger car operating on-road over the normal driving speed range. Both photographic and hot-wire anemometer techniques were employed. The measured airflow field, and other idealized ones, were used to select appropriate values for the tire heat transfer coefficient from previous GMR work. Tire power loss was then calculated with the GMR Combined Thermo-Mechanical Model to assess the importance of the airflow field on tire power loss. It was found that for the range of realistic flow conditions, tire power loss could be changed by up to 6% by the flow conditions alone.