Crr Values for clincher tires

[Scramman]

I have recently done a series of 10 coast downs each using two different clincher tire combinations. The results of the Crr seem high, but I don't have any real feel for what they should be. Total bike weight is 248 lbs and using both a 700x23C and 700x20 tire both at 120psi. Crr ranges from 0.0070 to 0.0074. Does this sound right? The road surface was smooth (not glass smooth but smooth) asphalt and the tests were done on the same stretch of road with only on minor very gradual turns. It seems high. Does the gradual turn make a difference?

[rruff]

What tires? What tubes? Bearings good?

[lorduintah]

And are the wheels true so that your brakes are not rubbing at any spot around the circumference?

All these - including the tires/tubes from above - factor in to Crr.

If your coast downs are consistent across the sample - with one not being an outlier - chances are you have a valid calibration.

Tom