Crr, CdA + calibration advice?

[JRandomUser]

Hi,

I've been using my PowerPod BLE for a few months now, and I'm still not sure if I have it calibrated correctly. I suspect that my configured Crr is too high, my CdA is too low, and that the fixed Cm is also too low. I've carefully performed an out and back calibration ride, the PowerPod is located away from any cables, in what I hope is clean airflow, but 'Check Calibration' suggests my wind scaling might be too high. I'm wary of just changing this stuff without a better understanding of what the correct values should be.

Some background information on me + my bike:
my weight: 62.5 kg
bike + gear weight: 16.5 kg
bike type: hybrid, wide flat handlebars
drive train: belt drive, Alfine 8 speed IGH
tires: 42mm Schwalbe Road Cruiser @ 60 PSI/4.14 Bar (cannot find any Crr data online for these)

I've attached three approx 17km out-and-back rides, all done early morning with little or no wind, and essentially no traffic on the middle few km. Road surface is good asphalt near the start and end, and not too rough tar + chip towards the middle/turning point.

Can anyone suggest if I should adjust Crr + CdA, and if so what to, ideally accounting for my tires, the road surface mix, my handlebars + riding position, and the presumed low mechanical efficiency of my drivetrain? And do I need to adjust my wind scaling factor?

Thanks!
James

[Velocomp]

Your ride files all look fine, and the calibrations are all good. This is easy to see because your wind speed is approximately the same as your bike speed, as it should be for an out-and-back ride.

Your Crr is fine, especially because you are using a hybrid bike, where rolling resistance is higher than typical road bikes.

Your CdA might be low: how tall are you, and what is your ride position? Do you sit more upright than you would on a conventional road bike?

[JRandomUser]

Thanks John, it's good to know my calibration is good.

I'm 1.72 m tall, riding position is more upright than a road bike - saddle height about same as handlebars, arms nearly straight and much further apart than they would be on the hoods of drop bars. Can you suggest a more appropriate CdA?

[Velocomp]

Modified profile is attached, with a CdA of 0.362, to account for the upright position.

Import the profile into Isaac, then transfer to your PP.

[JRandomUser]

Thanks John, will do.

[meste]

Your ride files all look fine, and the calibrations are all good. This is easy to see because your wind speed is approximately the same as your bike speed, as it should be for an out-and-back ride.

John, starting from your quote above, what approximately means, I see sometimes things like speed 28 wind 37 or speed 27 wind 40. I am trying to establish an algorithm to see when to do again my calibration.

Point number 2: I found Crr value for my tires, https://www.bicyclerollingresistance.co ... 0s-ii-2014 should I enter this data in my profile? Autocalibration had 0.0057, from the website would be 0.00387

Thanks,
Serban

[Velocomp]

If you wish you may use your Crr.

The important thing is to keep your profile consistent (and unchanged) so that you can compare results over time.