A disk drive is disclosed comprising a disk including a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval, and a head actuated over the disk. The spiral tracks are demodulated by reading a spiral track to generate a spiral track crossing signal g(x.sub.n), where x.sub.n is a time in a demodulation window, and determining a position error signal (PES) by determining a time-shift L that maximizes a correlation between g(x.sub.n) and a function that estimates a nominal spiral track crossing signal having the time-shift of L.