Abstract: A wheel balancer (1) for balancing an alloy wheel (2) comprises a support housing (30) and a main shaft (36) onto which the wheel (2) is mounted. A sub-housing (35) rotatably carries the main shaft (36), imbalance forces in the main shaft (36) and their respective directions are monitored for determining the magnitude and angular positions of balance weights required for correcting imbalances in the wheel (2) in selected balancing planes (17) and (18). A telescoping extendible sensor arm (54) is pivotally mounted about a vertical pivot axis on the support housing (30) for detecting balance weight receiving locations on the inner surface (10) of a wheel hub (4) of the wheel (2) at the selected desired balancing planes (17) and (18).