Abstract This paper gives data on transmission efficiency of various types of belts on cast-iron and paper pulleys and goes thoroughly into the transmissive power of oak-tanned and rubber belts on such pulleys with varying contact angle, a subject of importance in view of the prevalence of short-center drives with large transmission ratio. It is found that commonly used formulas for the effect of contact angle on transmissive power are not dependable for all combinations of belts and pulleys.