a wheel balancing apparatus for balancing an out - of - balance wheel that is mounted on a rotatable shaft includes force transducers positioned in a horizontal plane against resiliently supported bearings for the shaft to thereby detect horizontal components of the imbalance forces created by the out - of - balance wheel . photosensitive switches associated with the shaft produce phase - displaced analog signals , which signals are supplied to a pulse producing circuit for generating a train of count pulses on one of two output lines depending upon the direction of rotation of the shaft . a counter , which has a capacity exactly equal to the number of pulses generated by the pulse producing circuit per revolution of the shaft , is set when the horizontal component of the imbalance force for a particular correction plane associated with the counter equals zero . when a command to stop spinning the shaft has been issued , the shaft will slow down until it comes to a stop but the counter will continue to count through each cycle of shaft revolution so that it will stop at a position wherein the relative rotative position of the unbalanced weight can be determined . a digital - to - analog converter responsive to the counter output provides a ramp voltage to drive a null meter and thereby permit the operator to rotate the wheel after it stops until the position of weight imbalance for the particular correction plane is provided in the predetermined location for providing a corrective weight -- as is ascertained by bringing the null meter to the null position .