Powerpod calibration on two bikes. Need help.

[singh]

Hi All,
I'm using powerpod for about 7 months on one bike only and data was always consistent from ride to ride so i didn't care much about accuracy or number meanings.
Now i'd like to use pp on two bikes and it seems i can't get a correct calibration because power numbers i see on my Garmin seems too high (comparing with old setup) and very different from bike1 to bike2 doing the same effort.

this is my setup;
profile 1
bike weight about 9,5kg
tyres 700*25c
giroscopic speed sensor on front hub
standard powerpod mount

profile 2
bike weight about 7,5kg
tyres 700*25c
garmin speed sensor on front hub
combo out-front mount

attached you can find the two calibration ride i did in two weekends with each bike, my two profile and the 50km bike ride i did this morning with bike2.

What do you think, are they correct or there's something strange?
Thank you in advance

[singh]

Hi,
Can anyone help me?
Thank you

[Velocomp]

Please post .ibr ride files for each bike

[singh]

Sorry for the delay, I was waiting for new ant+ sensors to attach to bike#3 as the oldest one wasn't so good and gave strange readings.

this is the current setup;
profile#1
using out front mount and ant+ magnetless speed and cadence sensors. speed sensor on front hub.
did a calibration ride a few weeks ago and then a "check calibration" on a more recent out&back ride.

profile#3
using standard powerpod mount and ant+ magnetless speed and cadence sensors. speed sensor on front hub.
did a calibration ride today before the 15km rides attached.

Attached you can find 2 rides i did today, on the same route, with each bike. You can consider them as an out&back ride, i started from home and then turn back on the same road. i also tried to keep the same speed to see the differences on power output on my garmin during the ride and to have comparable files.

my feelings are that profile#3 is pretty good but profile#1 gives higher power numbers (maybe 30/40W). i also noticed strong power numbers fluctuations during profile#1 ride.

[Velocomp]

I looked at your ride files.

You've done a very nice job of calibrating each bike, and of controlling your riding so that they are nearly identical to each other.

I removed the first 8 minutes of each ride file, so that tilt calibration would not be a factor.

Because you did such a great job of riding, I was able to use the Power Meter Comparison feature (even though they are two different rides). In some places there is slight misalignment of time, but your eye can fix that...

You're correct that Profile 1 gives higher power numbers--after removing the first 8 minutes, about 20W higher.

But I think this is correct.

If you look at the PMC, you'll see that the riding conditions were close, but not identical. Though you held the same bike speed on both rides, wind conditions were a bit different. Where profile 1 wind is higher, in those sections watts are slightly higher. And note that your heart rate was SLIGHTLY higher on profile 1 ride--suggesting that you were working a bit harder.

I think you've done a great job with both setups. Have fun riding!

[singh]

Thank you John for your fast answer and your hard and precious work.
I can confirm you that profile#3 is very good and i will use it as benchmark to setup the other profile. Yesterday i did a 3 hour ride on prof#3 and power readings was in line with my feelings and with power numbers i have on my mind after months of PP use. You can find the ride attached, i enjoyed seeing everything working as expected.
Regarding prof#1, i will try to do another calibration ride when conditions are like they was last saturday (almost no wind and no traffic). Because the bike is 2kg lighter than the other I expected to have slightly lower power numbers going almost the same speed.

You are right, looking at my 2 rides files, power numbers between my two bikes are similar but the strange power fluctuation i see on the head unit during the ride of profile#1 gives me the feeling there's something wrong so i will try to tweak the profile a little more. I'm using dynamic smoothing on PP and instant power on head unit just to avoid this behaviour but power is going up and down continuosly. What can cause this fluctuation? something about aero or wind scaling values?
The bike is a Giant Propel and i read on another post that a guy uses these values for his Propel;
Aero 0.622, Wind scaling 1.930, CdA 0.322 on the drops. Friction 10.004, Crr 0.0044
Mine are;
Aero 0,528, wind scaling 1,436, CdA 0,368 on the hoods. Friction 10,469, Crr 0,0041
how can i compare these values? He rides on the drops and probably he is phisically more "aero" than me (81kg vs 67kg). Can both sets of values be correct or do you think some values are out of scale?

i'm sorry to bother you with all this questions, i'm new to power but very happy with Powerpod and all the informations i can get from it and isaac software, i just want to know more, and more, and more, and more.
Thank you.