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APPENDIX: Explanation and Comparison of Society of Automotive Engineers Test Procedures for Rolling Resistance
Pages 137-145

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From page 137...
... ."2 J2452 was approved by SAE in 1999. Its primary intent is "estimation of the tire rolling resistance contribution to vehicle force applicable to SAE Vehicle Coastdown recommended practices J2263 and J2264."3 COMMON FEATURES OF THE TWO TEST PRACTICES The two practices have common features such as test wheel diameter, surface texture, and ambient temperature.
From page 138...
... This is straightforward for P-tires, but it only applies to single-tire loading in the case of LT-tires.5 In J2452, P-tire base pressures are defined in the first table in the recommended practice. 4The design/measuring rim is the specific rim assigned to each specific tire designation to deter mine basic tire dimensions.
From page 139...
... In both practices load is defined in terms of maximum load. "Maximum load" is defined in both practices as the maximum load molded on the tire sidewall and listed as the load limit in the tire load tables of the current yearbook for the relevant tire and rim standards organization.
From page 140...
... With the tire loaded just enough so that it will continue to rotate, force or torque data, whichever are relevant for the test machine being used, TABLE A-3 Regulated Pressure Test Conditions for LT-Tires J1269 J2452 Test Point % Max Load % Base Pressure % Max Load % Base Pressure 1 100 110 20 110 2 70 60 40 50 3 70 110 40 100 4 40 30 70 60 5 40 60 100 100 6 40 110
From page 141...
... A matrix to remove this effect is derived during machine calibration. If errors exist because of machine load application alignment imperfections not fully compensated by the crosstalk matrix, the test must be run in both directions of rotation on force measurement rolling resistance test machines, and the results must be averaged.
From page 142...
... or 1.22 meters (48 inches) , which is used in federal vehicle emission and fuel economy tests.
From page 143...
... For J1269 P-tire fitting, For J1269 LT-tire fitting, In Equations 4 and 5, FZ is load, P is inflation pressure, and A0, A1, .
From page 144...
... Simplified Standard Reference Condition Because of the possibility of needing to produce data on a large array of tires, J2452 contains a Simplified Standard Reference Condition, which yields data at the following single condition. · Load = 70 percent of maximum, · Inflation = base + 20 kPa, and · V = 80 km/h.
From page 145...
... (88) E RBAN Standard MERF This is a MERF computed at the standard reference conditions discussed above.


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