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Old 04-20-2008, 04:42 AM   #19 (permalink)
IWillTry
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Join Date: Jan 2008
Location: Vancouver, BC, Canada
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If, for whatever reason, you want to measure Crr more accurately, without including drivetrain friction and viscous forces here is one method.

Use a spring scale to measure the force to pull your vehicle on flat ground at a constant speed (a walking pace). Call this force F1. Then jack up each wheel in succession, wrap a cord around the outside of it several times and use a spring scale to measure the force required to spin it at constant speed (walk away at the same walking pace as before). Add up the forces for all 4 wheels to get F2. Then Crr = (F1-F2)/Vehicle_Weight.

For even more accurate results, measure both drive wheels simultaneously (requires 2 spring scales and two people walking at the same pace).
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Last edited by IWillTry; 04-20-2008 at 07:12 PM.. Reason: oops, typo in formula
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