Unstable ride

[Wobblydrow]

Hi

Just as I thought i was getting settles with my powerpod I had a terrible experience today.

Started off on a bike and paired sensr first, no issue, then garmin, but still the slop / cda not showing on the garmin even after reboot

I thought that the numbers looked bad on the ride to start with, way way too high, then four times in the first hour or so the unit started to read zero watts for several minutes and then start again, but displaying 500+ watts instead of the expected 150-200 until the auto calibration kicked in. Still no cda/slope showing on the garmin. Eventually the zero power display problem disappeared. Eventually i saw my cadence sensor died ( flat battery i guess). The power display came back down from 500w, but still i reckon 30-50% higher than expected, my typical power on the flat would be ~150-170w, whereas even drafting was showing 200+. The average normalised power for the 96km ride was nearly 400w, should have been around 150w. The profile is correct for the bike. The file appears to show the wind and speed was being recorded by the unit, but no power on the file, its not a communication with the garmin thats the problem

We stops for a few minutes and then as soon as we started again the power jumped to an impossible 1000w+ for several minutes, when still riding on the flat...the sensor was showing 15% gradient, but had not moved in the mount. eventually the auto cal kicked in again.Only after we had a further stop for 15 minutes did the unit start to give a power that was around my realistic numbers for the last 10km of the ride (250w on a climb, 100-150w on the flat). By comparison two people with other PMs who are 75-80kg vs my 57kg heavier recorded average power at 145-150w each, so my average should have been around 120w give or take a bit.

Any ideas? , could the loss of a cadence sensor cause the power output to change by by disrupting the signal ? i find the only time i can get the wind and slope to display is right after doing a calibration, each time just turning my garmin on it never displays, no matter how many times i reboot. Also the average power my garmin was showing was way too high at 220w, does the dynamic smothng cause the garmin unit to over estimate the average?

Was a dry day, using a garmin speed sensor, only a couple of months old. mounted in a rigid mount not moving.

[Velocomp]

Your PP is rotating on its mount. This is why your watts are not stable.

[Wobblydrow]

Ok so PP locked in and now unmovable

I did two rides on two bikes back to back, I wanted to check if now being ultratight locked was going to change numbers i have seen, I rode an identical course on both bikes out and back. Both profiles previously had a 5km ride used as a calibration base. Today, i did a similar course as previous, only difference was the wind today was a bit stronger. I then used the calibration function in Isaac, which worked well and for both bikes gave me a normalised power within 5w, which i thought was reasonable. When i tried to upload the profile the software said for one the friction was negative and the other the slope was negative, so neither would allow profile loading. If these numbers have been spit out of the calibration software, why would it produce numbers that are not allowed to be used in a profile? What do i do to correct?
?
how do i determine what a correct calibration is, i have done a similar 5km ride twice, each time the values that the cal option spits out are totally different, for the same bike, on a comparable course, the only difference being one day was more windy than another.

In analysing the ride, I was expecting a symetrial match of the slope % , and whilst its not bad, some points are different, how mush is this affecting the calculation and if the unit is locked down hard and cant move, what would cause this?

[Velocomp]

Overall your readings are OK, but I suggest you do new calibrations for each bike, following the instructions:

1) Attach PP to your bike 1, pressing down gently near the button until PP locks against the mount. Then, tighten the screw so that PP cannot rotate

2) Do a calibration ride according to the normal instructions

3) Change profiles, then repeat the above steps for bike 2

4) Whenever you move from bike to bike, make sure you press down gently near the button until PP locks against the mount. Then, tighten the screw so that PP cannot rotate. This will ensure that PP is in the same rotational position each time you attach your PP to your bike

The reason you have strange friction numbers is because you're reattaching PP in a different angle from when the calibration was done.

Slope information is based on accelerometer and speed sensor readings. Your data is quite symmetrical. Slope is NOT used to calculate power, so variations in slope data have no effect on power.