Today, we will become a little more practical. After I calculated my theoretical CdA in the second part of our aeroCAST blog series, today, I will be showing you how to verify this in the field. To receive the most comparable results, I will have to use the same setup I did while racing. One of the most important points we cannot stop mentioning is the following: aeroFITTING is a process, which you have to conduct over a period of time. The largest impact on the windresistance has the human body and therefore you do not have to put too much emphasis on thinking about the enhancing your equipment and you can prioritize the optimization of your position. Here we assume that you have ideally already been set by a professional bikefitter on your bike.

Now, I will come to our aeroTEST which functions the following.


To receive the most accurate results it is important to repeat the same setup as often as possible. The first testrun functions for the program to be “calibrated” to the current climate conditions and to conduct accurate calculations. This is for our windfit and you can read more about that in a seperate blog. Therefore the first test run does not get incorporated into the results. After this run you will have to repeat every setup at least twice. Our recommendation is three test runs per setup if possible. For a verification in this example I will be conducting 8 test runs to receive a high number in accuracy.

Coming to the practical part: You are at your testing route with your setup and conduct the aeroTEST as described above. I conducted this procedure 7 more times without any changes.

After all testruns, either at home or at the test location via mobile internet, you just have to log in to the aeroDATA website. Now, I will lead you through the next steps. Then I will complete the data entry site of the aeroTEST with my data.


After completing this first part I will go to the testsuit and enter my testdata.

Now, I just have to connect my Garmin with my computer and upload my FIT files. The analysis will be done automatically as soon as I click on “Calculation”.

The first graph shows the expected time for the competition I aim for or which I want to use as a baseline. In our example I tool the data from Challenge Roth with 240w average power.

time advantages

The second graph displays the average CdA of all tests. As you can see this is calculated to 0,273 or 27.3 aeroPOINTS, which matches pretty exactly with the value calculated with our aeroCAST.


These two graphs will become more interesting if you perform the test with different setups. Now, if we scroll down, we will be getting closer to the more interesting details.
Here you can see the different test runs and their divertions. This was the first aeroTEST I did and therefore my testruns were not all 100% constant, which you can see in testrun 5 and 6. Unfortunately in testrun 5 I left my aeroposition and during testrun 6 I got passed by a car and streamlined a little bit.
time advantages

This last graph shows the CdA value of each test run. The measurement error of each test is also displayed graphically; if you want it can also be displayed numerically.

In both graphs our initial testrun which we used for our windfit is displayed at position number one.

With this data the process of aeroFITTING begins. Of course, you can do the next step on the same day, but you will have to wait till next week to read it here.