discrepancies

[Prmoulton]

PowerPod, Isaac, and Garmin. How come if I choose 20 minutes on the lower left area on Isaac it will give me a lower average power than if I choose a 20 minute area on the power graph, if I click a high spot on the power graph it is not the highest power (the area below the graphs tells the values at that point) and the power will go up higher and higher as the graph is going down? And how come when I try an FTP test Isaac says my highest power for 20 minutes is 300 Watts average, 306 if I choose the area myself, and my Garmin tells me 280 Watts for the highest 20 minute segment? The 20 Watt difference is pretty significant. My ego wants the 306 but am I really just 260 Watts?
Thanks,
Paul.

[Velocomp]

Please attach the .ibr file that is used in your post.

[Prmoulton]

John:
I have attached the .ibr file along with a URL for the Garmin analysis.
Isaac says Peak 20 min 307.9 W
My selection from power curve is 316.5 W for 20 minutes
GarminConnect says Maximum average for 20 minutes is 280 W
Why are these numbers different?

https://connect.garmin.com/modern/activity/1213100475

iBike_06_14_2016_1914_52_Miles.ibr

(1.06 MiB) Downloaded 185 times

[Velocomp]

1) Your PowerPod is slightly miscalibrated for wind; its wind readings are slightly low. This will cause somewhat low watts, the 280W you see in your Garmin.

2) The out-and-back portion of your route was auto-analyzed, possibly because you have "Auto Analyze" checked in the Edit/Edit Preferences/Analysis/Automatically Analyze Route

Screen Shot 2016-06-16 at 9.35.03 AM.png (68.31 KiB) Viewed 3338 times

3) The Auto Analyze function adjusted the calibration of your sensor, boosting watts to 308W (by the way, that is a good performance!)

4) With your PowerPod connected to Isaac, load this file again, then use the Analyze/Check Calibration command, and send your profile to your PowerPod. This will correct your future rides

By the way: your frictional road resistance Crr of 0.0071 is high. Unless you are riding a MTB or Crossbike, this number should be lower, around 0.0054

[Prmoulton]

Dear John:
Thank you. My Crr value was the default during set up. I have a road bike with Schwalbe One tubeless 25mm tires inflated to 65 psi. How do I get the appropriate Crr?
Paul.

[Velocomp]

Connect PowerPod to Isaac

Go to Edit/Edit Profiles

Select your profile

Click on the Advanced Tab

Click the radio button next to Riding Tilt (to hold the value)

You can now change Crr from 0.0071 to 0.0054

Click the Accept button, you'll get a Change Value message, click OK

Open the Edit/Edit profiles window again

Click Send to Device

You're all set!