Tilt correction out of range after calibration?

[djaustin]

I thought this would be interesting.

On my TT bike, I've moved the PP from the extensions to beneath the base bar (standard mount). The reason being that I want to test new arm positions and swap extensions. I rode 22 laps of my normal off-road calibration course last night and after the initial tilt adjustment, the PP reported power. The reading for power was, however much lower than I'd expect (about 140 watts) - bikecalculator would predict 200W. I've chopped off the last 11 circuits which I ran as a post-ride check calibration - it's a one mile circular circuit, and you can see that the wind/bike speed is clearly biased.

Now the odd part. When I run a Check Calibration to give a new profile, it gives me the expected 195 watts (which is the right answer). But when I try to upload this new profile to my PP, it says the tilt is -9 degrees and outside the range and won't upload.

Can you advise? I can move the PP back to the combined Garmin/Go Pro extension mount, once the new extensions are dialed in, I was just surprised at this finding.

[Velocomp]

Your PP internal slope setting so far away from correct that, when Isaac tries to fix it, you get an error message.

You should do a new, Best Accuracy calibration. This should fix things.

[djaustin]

Thanks.

Is that for only for the post ride calibration? The original mount had some tilt due to being on the raised extensions, so I couldn't mount it level. I've the mounted pod absolutely level on the base bars now, so I'll start again with a full calibration ride when the new extensions are delivered this week. I'm right in thinking I don't have to ride both ways - Just stop on 50W and restart?

[Velocomp]

No, you should do a complete, both ways, O&B calibration.

[djaustin]

Just a follow up for those interested. I rode an O&B calibration ride - basically three laps clockwise followed by three laps anticlockwise. Then I rode 11 laps to warm up and get a feel for target power. Finally I raced at a target power of 310 Watts per lap. Files attached for those that are interested.

Average power during the race was 312 Watts. Bikecalculator.com gives a prediction of 315 for 5% reduced Crr and 5% CdA - I'm pretty aero and run the fastest tyres ever tested on bicyclerollingresistance (Corsa Speed tubeless at 90 PSI). The race file includes an extra four laps with a different helmet at a power similar to the warm-up 11 laps, just to see if I could see much difference.

Very pleased with the results. And I won the race too

I won't be moving this Powerpod from the TT bike. I do however plan to couple it to a DFPM eventually for CdA evaluation.