A disk drive is disclosed employing a VCM control loop comprising a voltage detector operable to detect a back EMF voltage across a voice coil of a voice coil motor, a current detector operable to detect a current flowing through the voice coil, and a control voltage generator, responsive to a command input and the detected back EMF voltage, operable to generate a control voltage applied to the voice coil. Control circuitry within the disk drive (a) initializes the control voltage; (b) injects a transient into the VCM control loop and detects a corresponding current flowing through the voice coil; (c) adjusts the control voltage in response to a polarity of the detected current; (d) repeats elements (b) and (c) at least once; and (e) stores an offset value in response to the adjusted control voltage.