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Old 02-15-2012, 04:52 PM   #2 (permalink)
seifrob
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Join Date: May 2011
Location: Czechoslovakia (sort of), Europe
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Dáčenka - '10 Dacia / Renault Logan MCV 1.5 dCi (X90 k9k)
90 day: 47.08 mpg (US)
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Sorry if this thread is locked or banned any other way, but I have a (presumably) stupid question:

Did anybody considered use of personal scale to experimentally find out the rolling resistance instead of findig it out from graph?

As rolling resistance is a force (represented by Crr M g part of equation above), one could measure it directly:

Find a flat place (empty parking lot), have someone who can drive a car (or, at least, who can brake). Take a personal scale with you (mechanical preferrably - ie type that IKEA sells). Put your car to neutral, release hand brake. Ensure someone is sitting behind the wheel and knows how to brake. Push your car with the scale (you push the scale, scale pushes the car). Remember how many kgs you see on the scale, when you enter a steady speed. Repeat few times in both directions. Average the result, multiply by factor of your local gravitational acceleration (9,81 ms^-2 for us in central Europe) and you have rolling resistence force. (Or divide by your car actual weight to get Crr).

Is there a caveat I don't see?
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