Tried the "new" Cda analysis with Isaac 1.08
Have spend lot of time to get the Wind Scaling correct. 1.05 seems to be the correct number for me. (this is the middle number from 6-8 cal rides, from 0.98 to 1.08)
When analyse the CDA from lots of different rides I find this correlation between cda and speed.
At 40km/h cda is around 0.40
At 35km/h cda is around 0.35
At 30km/h cda is around 0.30
Lower cda with lower speed. Have also noticed this in the newton display.
I use a 0.006 crr for my MTB tires and 0.36 for cda.
Why different cda with different speed? Wrong tire crr or wrong Wind scaling?
One other thing. Please Velocomp, double the view time (or more) for cda in the Newton+ display. Really dangerous wating for the 2-3 sec the cda number shows before it dissapear while coasting.
Norbike
Newton+ CDA analysis with Isaac 1.08
Re: Newton+ CDA analysis with Isaac 1.08
Norbike,
I have observed similar results, depending on the road I think. This is providing you are seeing these trends repeatably.
If your wind scaling is indeed dialed and weight and all is correct, then Crr is the likely culprit.
I have three profiles set up with different Crr's for my rides for smooth, rough and mid. I usually ride with the middle Crr profile. When I select the correct profile for my ride, especially with smooth (less variation) I have gotten nearly consistent Cda numbers. I say nearly because there is usually a little gust or the like that will also cause variations in the readings.
This is also why in another post, I have suggested doing Cda measurements for real comparative usage, you choose smooth pave and get your Crr dialed. I think the consistency (averaged) of displayed Cda is a fair indicator of having the Crr dialed.
For Velocomp:
It would be very nice if the Cda analysis tool would respond to Crr tweeks in the Analise: tweek Cda, Crr, Cm function but it seems to only use the recorded ride file data or something.
This way, if my thinking is correct, the Cda analysis tool could be used to dial in Crr by looking for the analysis Cda value to become consistent during a decent with increasing speed!
Hope this helps (and hope I am correct
Russ
I have observed similar results, depending on the road I think. This is providing you are seeing these trends repeatably.
If your wind scaling is indeed dialed and weight and all is correct, then Crr is the likely culprit.
I have three profiles set up with different Crr's for my rides for smooth, rough and mid. I usually ride with the middle Crr profile. When I select the correct profile for my ride, especially with smooth (less variation) I have gotten nearly consistent Cda numbers. I say nearly because there is usually a little gust or the like that will also cause variations in the readings.
This is also why in another post, I have suggested doing Cda measurements for real comparative usage, you choose smooth pave and get your Crr dialed. I think the consistency (averaged) of displayed Cda is a fair indicator of having the Crr dialed.
For Velocomp:
It would be very nice if the Cda analysis tool would respond to Crr tweeks in the Analise: tweek Cda, Crr, Cm function but it seems to only use the recorded ride file data or something.
This way, if my thinking is correct, the Cda analysis tool could be used to dial in Crr by looking for the analysis Cda value to become consistent during a decent with increasing speed!
Hope this helps (and hope I am correct
Russ