Transient versus steady-state tire rolling loss testing.

A formula is developed for computing the energy loss per unit distance (or the "rolling loss") of tires operating under transient conditions. The formula is applied to two transient test schedules~a warm-up test with constant speed and zero torque (free-rolling), and an urban driving test with rapidly varying speeds and braking/driving torques. Test results indicate that the average rolling loss during warm-up is 9%, and during urban driving, 26 to 47% higher than the steady-state rolling loss. Equipment problems associated with transient testing are indicated.