A ride with my iBike and PowerTap

[Velocomp]

I have my trusty iBike Gen II on my bike as well as a variety of direct force power meters. Today, the DFPM was my PowerTap.

Earlier this year I used one of the new features of iBike 2 to determine my drag coefficients with and out-and-back ride where the PT is used as the direct-force power reference. This isn't "cheating"; rather, it's a way to have two different measurement devices (the iBike and the PT) be calibrated so that they perform similarly for a given set of ride conditions.

I rode 17 miles today on Montana chip-sealed roads, including the rumble strips on the side of the road. Prior to the ride I let the iBike acclimate to outdoor temperature, then I performed a tilt calibration and wind offset. That was it; the rest was riding.

After my ride I used the iBike 2 software to marry the iBike and PT files together.

I thought you might be interested to see the results. You can download and view the attached file; you'll find that the two devices differed by 0.1W (out of 160) for average power and by 38W out of 780W for maximum power (when I look at the shape of the power burst I find the PT peak data somewhat suspicious).

Also, play around some with the power meter comparison and you'll see that the moment-to-moment data is extremely close.

A lot of this ride was on reasonably flat roads where wind is a major factor. This means that the CdA and Crr measurements were very good. In general I held the same ride position for most of the ride; you should be able to tell from the CdA vs time analysis where I moved around some.

[Velocomp]

Here's an image from the power meter comparison. The top graph shows power vs time; you can see that the two devices are virtually indistinguishable. The bottom graph is power differences which, again, are minimal.

[michaeltop]

Ditto for my IAero and powertap . This little fellow has really come of age.

Outstanding upgrades.
Thanks to the entire Ibike team.

Michael