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SAE J2452 2017 Edition, July 1, 2017
Stepwise Coastdown Methodology for Measuring Tire Rolling Resistance
Description / Abstract:
Scope
This SAE Recommended Practice is applicable to pneumatic Passenger Car "P" Type, Light Truck Metric, and Light Truck High Flotation tires, or similar tires approved by bodies other than Tire Rim Association. The methodology is applicable within normal operating ranges of vertical load and inflation pressure, and for velocities between 115 km/h and 15 km/h (71 mph and 9 mph) during a relatively short duration event such as a coastdown. This procedure is applicable only to operation in the free-rolling mode at zero slip and camber angle for ambient temperatures between 20°C and 28°C (68°F and 82°F) and for surfaces with diameters of 1.2 m (48 in) diameter or greater. Details regarding the equipment, tires, and test methods used specifically for validation of this document are included in Appendix A. Two basic measurement methods covered by this document are as follows
Force Method
Measures the reaction forces at the tire spindle and converts it to rolling resistance. The chief advantage of this method is that the only parasitic losses in the measurement are tire spindle bearing losses and aerodynamiclosses associated with rotation of the tire and its wheel. The main disadvantage is that the measured spindle force can contain large errors caused by load misalignment and load-spindle force interaction ("crosstalk"). Elimination or compensation of these effects is necessary. A minor disadvantage is that the loaded radius of the tire must be measured in order to convert spindle force to rolling resistance
Torque Method
Measures the torque input to the test machine and converts it to rolling resistance. The advantage of this method is that the measurement is direct: rolling resistance is the net torque divided by the test surface radius. The main disadvantage is that parasitic losses contained in the measurement include rotational test wheel losses as well as tire spindle losses. Hence, the parasitic losses are larger than those of the force method and can be of the same order of magnitude as the rolling resistance itself. Accurate measurement and compensation for these losses is necessary. Speed hunting oscillation in the drive motor can also induce large measurement errors due to the high moment of inertia of the test surface
This SAE Recommended Practice is applicable to pneumatic Passenger Car "P" Type, Light Truck Metric, and Light Truck High Flotation tires, or similar tires approved by bodies other than Tire Rim Association. The methodology is applicable within normal operating ranges of vertical load and inflation pressure, and for velocities between 115 km/h and 15 km/h (71 mph and 9 mph) during a relatively short duration event such as a coastdown. This procedure is applicable only to operation in the free-rolling mode at zero slip and camber angle for ambient temperatures between 20°C and 28°C (68°F and 82°F) and for surfaces with diameters of 1.2 m (48 in) diameter or greater. Details regarding the equipment, tires, and test methods used specifically for validation of this document are included in Appendix A. Two basic measurement methods covered by this document are as follows
Force Method
Measures the reaction forces at the tire spindle and converts it to rolling resistance. The chief advantage of this method is that the only parasitic losses in the measurement are tire spindle bearing losses and aerodynamiclosses associated with rotation of the tire and its wheel. The main disadvantage is that the measured spindle force can contain large errors caused by load misalignment and load-spindle force interaction ("crosstalk"). Elimination or compensation of these effects is necessary. A minor disadvantage is that the loaded radius of the tire must be measured in order to convert spindle force to rolling resistance
Torque Method
Measures the torque input to the test machine and converts it to rolling resistance. The advantage of this method is that the measurement is direct: rolling resistance is the net torque divided by the test surface radius. The main disadvantage is that parasitic losses contained in the measurement include rotational test wheel losses as well as tire spindle losses. Hence, the parasitic losses are larger than those of the force method and can be of the same order of magnitude as the rolling resistance itself. Accurate measurement and compensation for these losses is necessary. Speed hunting oscillation in the drive motor can also induce large measurement errors due to the high moment of inertia of the test surface
SAE J2452 2017 Edition, July 1, 2017
Stepwise Coastdown Methodology for Measuring Tire Rolling Resistance