New to power and wondered if I could use my ride this am to estimate CDA. Loop course.
42.86 miles
2:02:45
20.95 mph
Average Power 194, NP 198
1,821’ elevation gain through Garmin 800. (although a loop with start and stop at my house so really no gain?)
Temp 75-80deg.
FTP 300
Weight of me and bike 84kg
Winds were slight (under 8mph)
Cannondale Slice, aero helmet for the ‘test’, wheels, Mavic Ascium, roads a mix of asphalt and chip seal (3:1 ratio?). Michelin Pro3 tires (old race tires)
I do not have a very aggressive opinion imho. Was fit at Elite bicycles about 7 months ago
So when I was playing with Golden Cheetah or Analytic cycling it puts me at a very ,low CDA, which I highly doubt.
Am I missing something (a lot of things?)?
It was coming up with numbers in the 0.2 range. Not believing it, so I bow to the experts to tell me how I can do this better?
New to power and wondered if I could use my ride this am to estimate CDA. Loop course.
42.86 miles
2:02:45 20.95 mph Average Power 194, NP 198
1,821’ elevation gain through Garmin 800. (although a loop with start and stop at my house so really no gain?)
Temp 75-80deg.
FTP 300
Weight of me and bike 84kg
Winds were slight (under 8mph)
Cannondale Slice, aero helmet for the ‘test’, wheels, Mavic Ascium, roads a mix of asphalt and chip seal (3:1 ratio?). Michelin Pro3 tires (old race tires)
I do not have a very aggressive opinion imho. Was fit at Elite bicycles about 7 months ago
So when I was playing with Golden Cheetah or Analytic cycling it puts me at a very ,low CDA, which I highly doubt.
Am I missing something (a lot of things?)?
It was coming up with numbers in the 0.2 range. Not believing it, so I bow to the experts to tell me how I can do this better?
Thanks.
I won’t comment on the actual CdA part. Though if you are worried about consistency, having a 40 mile loop on which to do CdA estimation is not as desirable as having a 3 mile (or even a velodrome) on which to do the estimations.
That said, given the weight and power put out, the CdA sounds about right and i’d expect it to be in the high 0.2x range. For comparison, for me to average 21mph on a 6mile loop with 350ft climbing per lap, i better put out 235W, with rider + bike weight of 80kg. This is done on a road bike with an rather aggressive position.
As someone has pointed out, that’s a very long ride file. I’d find it hard to believe you would be able to hold a position constant throughout the ride. And 8mph is not considered “slight” for this kind of thing.
Really, try a very short ride consisting of at least 4 loops on a windless day. Each loop should be under 1km long. Give yourself every chance to eliminate errors if the answer is really important to you.
Am I missing something (a lot of things?)? If you were using Aerolab in GC I believe you need to do it on a loop with no braking. As others have said, this is difficult to do on a 40 mile loop. It looks like you hit the brakes a few times.
Only thing I would add is you need to really fine tune for RR and air density to get precise absolute values. I usually do quick work in aerolab and see if one thing is faster than the other. As long as I am able to acurately identify small improvements, the exact CDA is gravy. I do have a bunch of data showing 25mph at 220-240 or so watts, so I am in pretty good shape.