Tire wear data from two tread wear tests on different courses have been analyzed to determine how patterns of wear are affected by the course. The coefficient of variation (CV) was used as a measure of irregular wear. Tires which exhibited irregular wear (large CV) exhibited the same pattern of wear on both courses; that is, the location of the fastest wearing ribs was unchanged. Those that wore more evenly showed distinct differences in wear pattern on the two courses although all ribs wore at about the same rate. However, some of the changes observed for particular brands of tires may have been the result of tire design changes. Tread life was projected for tires based on the fastest disappearing groove and on the average of all groove depth readings. The rankings of the tires by both methods on the two courses were highly correlated; there does not appear to be any advantage to one method over the other for relative rating.