Abstract: A wheel balancer comprises apparatus for determining the radius of a rim of a hub of a wheel and for determining the distance of the inner and outer side walls of the hub from a reference plane. A framework which is pivotal downwardly over the wheel to be balanced carries a pair of ultrasonic transducers to determine distance of the sides of the wheel from the reference plane. A transducer monitors the position of the framework. The distances monitored by the ultrasonic transducers are stored in a microprocessor against the corresponding positions of the framework at intervals on movement of the framework. The ultrasonic transducers detect a large change in distance from the reference plane caused by the hub well periphery. The hub rim radius is computed from the well periphery radius, while the distances of the side wall from the reference plane is obtained by looking up the stored values of distances which corresponds with the appropriate position of the framework for the hub rim radius.