Estimates of wear rate ratios for the two tire brands tested vary in replicated experiments run concurrently or after intervals of weeks or months. This study reports tests made on different car models, and repeated several weeks later. Rim width and shock absorber stiffness were also studied for their contribution to wear rate variability. Alignment settings for all cars were fixed at the midpoint of the manufacturer's specification range, and were frequently checked and adjusted if necessary. Hitherto unreported data from former experiments that were run under various controlled alignment procedures are reported here. No evidence was found in the present experiments that differences in car models, rim width, or shock absorber stiffness contribute to wear rate variability. The average wear rates in the several experiments varied by 30%, but the ratios of the tire brands varied by only ± 2.23% around the mid‐range. The variations among cars when alignment settings were frequently checked and adjusted were characterized by a standard deviation of less than 0.20 mils/1000 miles (0.008 mm/1000 km).

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