CdA changing during the Ride
Posted: Thu Feb 28, 2019 7:57 pm
Hi John,
I've recently noticed that during the rides the CdA that is used by the PP (and Isaac) to calculate power is changing and not what was defined on the profile (I'm not using a DFPM). I would like to understand why the PP is doing that, because it is doing exactly the opposite to what I'm really doing on the bike (decreasing CdA by moving to the drops). The attached file is an example, during the segment from the km 95 to 105 I was on a high tail wind and downhill (around -2%), during that time I was on the drops instead of hoods, so I was expecting a higher than normal power output, but it was too high for a small difference on CdA. When I opened the ride on Isaac and use the power meter comparison tool (or the data on the CSV), the CdA used during that segment was 0.55 instead of 0.35 from my profile. Is there a way to tell the PP not to do that and stay with the CdA on the profile? Is that change related to the Speed,Tail wind or what causes the PP to start wild guessing the CdA? I have seen that on almost all rides and if I tried to change the CdA, the offset doesn't go away.
Thank you for your help and for an excellent product.
I've recently noticed that during the rides the CdA that is used by the PP (and Isaac) to calculate power is changing and not what was defined on the profile (I'm not using a DFPM). I would like to understand why the PP is doing that, because it is doing exactly the opposite to what I'm really doing on the bike (decreasing CdA by moving to the drops). The attached file is an example, during the segment from the km 95 to 105 I was on a high tail wind and downhill (around -2%), during that time I was on the drops instead of hoods, so I was expecting a higher than normal power output, but it was too high for a small difference on CdA. When I opened the ride on Isaac and use the power meter comparison tool (or the data on the CSV), the CdA used during that segment was 0.55 instead of 0.35 from my profile. Is there a way to tell the PP not to do that and stay with the CdA on the profile? Is that change related to the Speed,Tail wind or what causes the PP to start wild guessing the CdA? I have seen that on almost all rides and if I tried to change the CdA, the offset doesn't go away.
Thank you for your help and for an excellent product.