The design and development of a machine to measure tire energy dissipation over transient driving cycles is described. The main feature of the machine is that two tires are loaded against each other across a steel belt which runs on 762-mm diameter steel drums. One of the wheels is driven to follow a transient driving cycle representative of typical passenger car use; the other wheel is allowed to roll freely. Energy dissipation in the driving tire is measured by subtracting the energy leaving the tire from the energy entering the tire. An error, ascribed to small deformations of the belt in the tire contact area, was found in the tire energy measurement. This error is a function of the construction of the tires installed on the machine. A number of modifications to the machine and the test procedures are suggested to improve the accuracy of the energy dissipation measurements. Typical energy dissipation measurements for C-14 tires are presented.