Last week, we introduced our aeroTEST and verified the calculated CdA (windresistance) value. Today, we will start the work on optimizing the aerodynamic position in order to gain time. In our example, my CdA was 0,27 m2 (27 aeroPOINTS), a value which is ok, but can easily be enhanced according to our experience. As already mentioned, the human body is responsible for approximately 80% of the aerodynamic drag, depending on your specific type of bicycle. The remaining 20% is covered by your equipment and gravity. For that reason, we will focus at the moment on optimizing your body position. As we already mentioned, the starting point is an already completed bikefit by a professional bike fitter to ensure that you are biomechanically well positioned on your bike. In an optimal situation your bikefitter and aerofitter are the same person or working closely together. In my case, I was fitted by Fritz Buchstaller, with whom Aerotune is cooperating as well. This is important, because due to location issues I was not able to conduct this part with the presence of my bikefitter. We had to do some modifications which had some influence on my biomechanics and it was good to be in the scope of the initial bikefit, but this position must be reassessed by my bikefitter.
As an initial startpoint, we took pictures and videos of me during the conduct of the aeroTEST to see how my position is under stress, how my head position is under movement and how my chosen aero helmet aligns with my torso. This has a great influence on the CdA, since the head is the first larger bodypart which hits the wind. We did this step first, since we were already out in the field. If you are doing this on your own, this can be done by a friend who accompanies you, what we highly recommend.
In the second step, we did the same, just on a turbo trainer, checking my position from 360 degrees by taking pictures and videos, with and without helmet. It is important to conduct both series, since both have advantages and disadvanteages and to have a definite evaluation the most accurate available visual data is recommended. The turbo trainer gives the advantage, that you can easily measure, evaluate und modify the position. However, the disadvantage is, that it is artificial and does not incorporate climate, road conditions and full bodymovement into the picture. The field analysis gives a pretty good visual picture, however, if nobody constantly drives beside you in a vehicle, it only gives you a picture at a fixed place and given moment of time and it is a lot more difficult to receive 360 degree footage.
We found that my head position was a little too high during the field test. On the turbo trainer, I had kept it tucked in pretty well. In addition, my choise of aerohelmet was ok, but the gap between my helmet and my torso was improveable. By lowering my aerobars a little bit and raising the angle a little, I was able to keep my head lower and aerodynamically better aligned. This however had some influence on the ability of the rotation of my pelvis. That is why it is important that aerofitting and bikefitting go hand in hand together.
In the next step, we will go back to verify this slightly changes with our aeroTEST and in next weeks blog you can read about the results.