Standard Practice for Radial Light Truck Tires to Establish Equivalent Test Severity Between a 1.707-m (67.23-in.) Diameter Rotating Roadwheel and a Flat Surface

Abstract

5.1 Historically, tires have been tested for endurance by a variety of test methods. Some typical testing protocols have been: (1) proving grounds or highway testing over a range of speeds, loads, and inflations, (2) testing on fleets of vehicles for extended periods of time, and (3) indoor (laboratory) testing of tires loaded on a rotating 1.707-m diameter roadwheel; however, the curved surface of a 1.707-m diameter roadwheel results in a significantly different tire behavior from that observed on a flat or highway surface. 5.1.1 This practice addresses the need for providing equivalent test severity over a range of typical tire operating conditions between a 1.707-m diameter roadwheel surface (Practice F551) and a flat surface. There are different deformations of the tire footprint when loaded onto curved surfaces versus flat surfaces resulting in different footprint mechanics, stress/strain cycles, and significantly different internal operating temperatures. Since tire internal temperatures are key parameters influencing tire endurance or operating characteristics under typical use conditions, it is important to be able to calculate internal temperature differentials between curved and flat surfaces for a range of loads, inflation pressures and rotational velocities (speeds). 5.2 Data from lab and road tire temperature measurement trials were combined, statistically analyzed, and tire temperature prediction models derived.2 5.2.1 The fit of the models to the data is shown as the coefficient of determination, R2, for the critical belt edge: R2 = 0.90 Two Standard Deviations (2-sigma) = 3.2°C (that is, 95 % of the variation from the means is within ±3.2°C) 5.2.2 These prediction models were used to develop the prediction profilers outlined in Section 7 and Annex A1.