An improved method for determining an initial flat spot magnitude on a tire that has been resting for a period of time on a substantially flat surface uses regression analysis. In accordance with the method, values of a tire flat spot magnitude for a particular type of tire are determined at a number of measurement intervals by a uniformity machine that spins the tire. An equation having at least two exponentially decaying terms is then determined that corresponds to the measured data points. Regression analysis is then used to determine an estimate for an initial flat spot magnitude. The method can be used to evaluate the effectiveness of different tire designs with respect to flat spot recovery rates.