Although there are over 20 organizations in the United States engaged in tread life evaluation by average groove depth measurements, no previous attempt has been made to compare the results obtained by the variety of procedures in use. Therefore, ASTM Committee F‐9 on Tires organized an experiment in which four tires were measured at 14 laboratories representing most major tire producers and independent test houses. Each participant measured the tires following his normal practice. In several laboratories the tires were measured by each of their operators.
The data show in general that there are significant differences between laboratories but none between operators within a laboratory. Precision and accuracy vary between laboratories. Practices between laboratories vary greatly with respect to the number and locations at which measurements are made. On ribbed tires, 7 of 14 measured all grooves at 10 positions in each. For snow tires, there was no most common practice.