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One of the objectives of laboratory measurements of tire rolling resistance is to compare tires. This requires that a common basis be established for this comparison. For tests performed per the current standard, SAE J1269, rolling resistance measured at a standard load/pressure condition, at 80 kph, is used for this purpose. However, a similar specification should not be used for rolling resistance measured as per the new standard under development, SAE J2452, because the data are collected at multiple speeds for each load/pressure condition. This paper explores alternatives, defines new parameters and proposes a new methodology for comparing tires using data generated as per J2452. The new parameters are MERF (Mean Equivalent Rolling Force) and SMERF (Standard Mean Equivalent Rolling Force). The mathematical derivation of these terms is presented and their use illustrated using laboratory rolling resistance data generated as per J2452.

This study addresses the issue of modeling laboratory rolling resistance data, collected following standard test procedures. A brief reference to the current method, SAE J1269, and the models used therein, is followed by a discussion on development of new models that also account for the effect of speed on rolling resistance. A model is proposed that represents rolling resistance data over a range of speeds and can be used to predict rolling resistance at various load, pressure, and speed combinations, other than the test conditions. Further, the same model is effective in modeling passenger car as well as light-truck (LT) tire data.