Significance and Use
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 on curved versus flat surfaces resulting in different footprint mechanics, stress/strain cycles, and significantly different internal operating temperatures for the two types of contact surface. 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.
Scope
1.1 This practice describes the procedure to identify equivalent test severity conditions between a 1.707-m diameter laboratory roadwheel surface and a flat or highway surface for radial pneumatic light truck (LT) tires.
1.1.1 Tire operational severity, as defined as the running or operational temperature for certain specified internal tire locations, is not the same for these two test conditions. It is typically higher for the laboratory roadwheel at equal load, speed and inflation pressure conditions due to the curvature effect.
1.1.2 The practice applies to specific operating conditions of light truck tires up through load range E for such tires used on vehicles having a gross vehicle weight rating (GVWR) ≤4536 kg (10000 lb).
1.1.3 The specific operating conditions under which the procedures of the practice are valid and useful are completely outlined in Section 6, (Limitations) of this standard.
1.1.4 It is important to note that this standard is composed of two distinct formats:
1.1.4.1 The usual text format as published in this volume of the Book of Standards (Vol. 09.02).
1.1.4.2 A special interactive electronic format that uses a special software tool, designated as prediction profilers or profilers. This special profiler may be used to determine laboratory test conditions that provide equivalent tire internal temperatures for the belt edge region for the two operational conditions, that is, the curved laboratory roadwheel and flat highway test surfaces.
1.2 The prediction profilers are based on empirically developed linear regression models obtained from the analysis of a large database that was obtained from a comprehensive experimental test program for roadwheel and flat surface testing of typical radial light truck (LT) tires. See Section 7 and the research report2 for more details.
1.2.1 For users viewing the standard on CD-ROM or PDF, with an active and working internet connection, the profilers can be accessed on the ASTM website by clicking on the links in 7.5 and 7.6.
1.2.2 For users viewing the standard in a printed format, the profilers can be accessed by entering the links to the ASTM website in 7.5 and 7.6 into their internet browsers.
1.3 For this standard, SI units shall be used, except where indicated.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.