AeroPod, PowerPod and Newton

I was following the calibration checking procedure by going to the coast screen and just wanted to verify if I did it right. To start with my unit seems like it is giving good numbers on climbs and even flats , but I was getting like 100-200 watts while coasting downhill at 25-30mph. This is when I read about the calibration checking procedure so I figured why not give it a try. I went into coast screen and coasted down a 1% grade doing apprx. 25-30 miles hour. I took the numbers that were high and not close to zero and went into IB3 and adjusted AERO in my profile down about 10%. My numbers/watts are much lower in the coast screen and while in the normal power screen to(50 watts or so) but still not close to zero. My CDa was .460 and Aero was .296

Dropped my AERO to .257 and my CDa went down to.400
Just for the record this is on a mountain bike I use for training on the road.

My question is this, should I keep lowering my Aero more until my watts are around zero (right now it is around 40-60watts) on the coast down screen or am I risking it changing my power numbers on climbs and /or flats.

Thank you,
Clint

You are risking changing the numbers on the flats. . .although if you are coasting downhill and seeing high power numbers, then your watts are likely a bit off on the flats (but not as much because of the lower speeds). As for climbing, almost all of your wattage is used to overcome gravity (not aerodynamic forces) so it's likely your climbing wattages won't change much.

This will probably be the best way for you to dial in your cda. I know you have had some problems getting it properly set on the mtb, and it can be tough getting this dialed in when the input variables are less than ideal. I think what you are doing, coasting down a hill at about 25mph while in the coast screen so you can see positive or negative watts is going to be your best option. If you wanted to do these tests on the bike, you could use the estimated cda for this, but keep in mind that you will need to have your weight be much higher than it actually is to compensate for the higher cda of riding a mountain bike.

Thanks coach Boyd. You have really, really helped me a lot. I have spent a lot of time reading all of the posts on the forum here to get a better understanding of things, and so far I think I am understanding settings and tweaks a little more.


But now, just when I think I am starting to understand something I get another curve ball (lol)....changing my weight, and how much to change it to??
I usually will not have a lot of super high speeds in a race,so just getting close will do for me. I just thought that 100-200 watts at 27 mpg was a little to high.
As of right now I am very satisfied with my unit other than the higher downhill coast numbers, which are a lot lower now after I lowered my aero down by about 10-15% which then of course lowered my CDA a bit to. Also my riding position on my bikes is almost if not more forward /down than riding on the hoops if that matters.
What I am going to do is adjust both of my bikes down until the number are close to what they should be on the coast screen and then I will post my profiles for each bike, along with a ride file or race file for each bike also. Then maybe you or someone on the forum here can look and see how my FINAL results look to my profiles. I race again this weekend so I should have the files early next week. After this, the only thing I want to make sure of is that both bike are comparable in the wattage area so that I can go back and forth between the bikes using the same FTP number.

Thanks again in advance,
Clint