Transcon has gained extensive operating experience with tubeless, 11.00 x 22.5, nylon cord, bias ply construction tires mounted on 7.5 x 22.5 aluminum wheels. The six year period of 1970 thru 1975 will be discussed, further supported by data derived thru September of 1976. During this period, the significant factors and operating parameters affecting tire durability have not changed. Engine horsepower, geared speeds, average loads, routes and type of operation have remained constant. Pertinent fleet facts are summarized in the Appendix for the period 1970 thru 1975.