Abstract: A method to balance spindles in a plurality of disk drives is disclosed and claimed. An initial imbalance and initial phase for one of the plurality of disk drives is determined, the determination depending upon an amplitude and phase calibration. One of a plurality of balancing masses is selected based on the initial imbalance and attached at an angular position selected based upon the initial phase. A final imbalance after attachment is similarly determined. These determinations are repeated for each of the plurality of disk drives, with the final imbalance and the initial imbalance recorded for each. The amplitude calibration is adjusted based on a comparison of a measured distribution and a theoretical distribution of the final imbalance versus the initial imbalance.