Abstract: A method for applying an optimal seeking technique to a disk file with excessive repeatable runout includes a method of modifying a control signal for a rotary actuator arm of a disk drive. The control signal is modified during track seeking by adding a runout state that is calculated each time a servo sector of a target data track on a surface of a disk is sampled by read/write heads carried by the actuator arm. A calibration algorithm can be used during track following to determine runout magnitude and runout phase at various preselected calibration tracks on the surface of the disk. A seeking algorithm can be implemented to compensate for the relative runout magnitude and phase variations between present and target tracks.