A new design and test procedure for characterizing the friction interface between an accessory V-ribbed drive belt and it's mating pulley has been developed. The procedure is a dynamic test, to best simulate the accessory or drive pulley under real conditions. Consistent, large variations in the dynamic coefficient of friction of different belts were found. Both wet and dry conditions were investigated. This paper describes the new test procedure and its benefits. It also provides some fresh insights into variations in friction properties of different belts and pulleys under different conditions.