A computer process establishes data frequencies for recording data in zones of a zone bit recording medium in a disc drive. At least three data points are identified for each zone correlating data frequencies and corresponding bit error rates, and a slope of a curve between each two data points is calculated. The slopes are averaged, and the data frequency is calculated based on the average slope. If a difference between the average and default slopes exceeds a first threshold value, or if a spread of the slopes exceeds a second threshold value, the data frequency is calculated based on the average slope and the default slope. In one embodiment, each of the three data points is generated by recording data in the zone at each of three selected data frequencies, reading the recorded data, and calculating bit error rates based on the recorded and read data.