This paper presents research results from the first phase of a project to develop a tire fuel efficiency consumer information program for passenger vehicle replacement tires. In this phase of the project, the agency completed a test program using 600 tires of 25 model/size combinations to evaluate five different rolling resistance test methods. These test methods were derived from two SAE and two ISO standards. The test matrix included two separate test laboratories to examine lab-to-lab variation.

The results indicated that all of the five test methods had very low variability and all methods could be cross-correlated to provide the same information about individual tire types. While multi-point rolling resistance test methods are necessary to characterize the response of a tire’s rolling resistance over a range of loads, pressures, and/or speeds, either of the two shorter and less expensive single-point test methods were deemed sufficient for the purpose of simply assessing and rating individual tires in a common system. The single-point ISO 28580 draft international standard has an advantage over the single-point SAE J1269 recommended practice because it contains a lab-to-lab measurement result correlation procedure. There was a significant offset observed in the data generated by the two laboratories when using the identical test, even when testing the same tire, which must be accounted for in a rating system. Results show that for all the tests conducted, lab-to-lab variation can be statistically minimized if data from each lab is normalized to the test results of a Standard Reference Test Tire (SRTT). Two additional retests of a given tire did not produce statistically different rolling resistance values from the first test. So the concept of limited retesting of the same tires for lab alignment or data quality monitoring appears valid.