The tyre represents 85 % of the total of the frontal surface of the wheel.
Thus, it is essential not to ignore it in the study of aerodynamics. Most wheel manufactuerers who study aerodynamics do not consider the tyre as an integral part of the wheel. However, a very aerodynamic wheel cannot give good results with a tyre that is not aerodynamic. With CX01 technology, for the first time, a wheel and a tyre are designed together as an unique element.
To eliminate turbulence, the tyre and the rim have to guarantee perfect airflow. This is why the CX01 tyre and rim are shaped to match perfectly together. These specific CX01 profiles, combined with the CX01 blade, eliminate the turbulences between the tyre and the rim.
As on the wings of certain planes, the CX01 profile smooths the total surface of the wheel-tyre system and guides airflow across the rim, reducing the total drag of the system.
To achieve extremely precise results, we developed a rigorous measurement approach
To connect laboratory results with the reality on the road, it is important to conduct 2 types of tests:
- Tests are made by engineers with athletes in the wind tunnel. This testing measures the wheel's aerodynamic drag in a closed and controlled environment.
- Measurements are taken outside, on the road, thanks to specific equipment fixed to the bike. A weathervane allows measurement of the angles of incidence of the visible wind, which is a combination of weather wind and the wind due to forward velocity.
This tool allows comparison of wind tunnel measurements and real-world riding conditions in order to be certain about the validity of any performance gains measured.
By studying the results obtained in wind tunnels and the measurements made in real conditions, we can quantify gains obtained in term of aerodynamic drag reduction. Thanks to a weighting law, the gains are adjusted for real-world conditions.
- The performances of the CXR80 are represented by the yellow line on the graph. CXR80 wheels allow a rider to save 6.4 watts of power output, in comparison with the most aerodynamic wheels available in this category.
- Again by comparison, with a yaw angle of 18 °, the CXR 80 allows as much as 25 watts power savings.
- But the most surprising is that between 14 ° and 19 ° of effective headwind, the wheel actually generates speed thanks to negative (forward) drag force.