Fact: The vast majority of a cyclist's power output goes into overcoming air resistance.
We design and test our frames with this reality in mind. Like many other companies in the industry, we put our time in the wind tunnel to minimize aerodynamic drag. Contrary to others, however, we believe that measuring static frames by themselves in the wind tunnel delivers an incomplete and misleading portrait. We're not the only ones:
"Roughly 75-80% of aerodynamic drag is due to rider position. Rider position is [most] important."
This opinion, held by the vast majority of aerodynamic experts, was put to the test in a recent study done at the National Research Council of Canada:
I. The aerodynamic profile of our Crono and Magis frames – based on varying wind speeds – was scientifically measured and compared to that of two leading, competitive TT/Tri frames (stock models). The results can be summarized as follows:
II. The test then proceeded to take two frames sets, GURU's Crono and Competitor 1, build them up with the same components/wheels, and measure their relative CdA with riders on them. In order to permit valid results, two different subjects (one male, one female), each with a different custom position, were tested on the Crono. The subjects' respective position was then replicated as close as possible** on the C-1 bike. The normalized results of this static aerodynamic test, combining bike and rider, were as follows:
III. Because bikes were not made to stand still, the test proceeded to measure the relative aerodynamic profiles of the same two riders on the same two bike models (four tests in total), this time in a more "real life" context: with cyclists pedalling over an extended period of time***. The normalized results were as follows:
The element that most negatively impacted the aerodynamic profile over time for either subject was the movement of the upper body and head, as illustrated by the following data:
There is also evidence that bike handling has a significant impact on aerodynamics as the slightest side-to-side motion would appear to increase relative CdA (as more of the rider/bike profile becomes exposed to the wind).
While some of the comparative elements of this test merit more study, it clearly confirmed the original hypothesis: aerodynamics on a bike are primarily a function of the rider's position (and relative immobility). Anyway you cut it, a bicycle frame represents a relatively minor portion (less than 10%) of the total potential drag created by a rider on their bike. Ultimately, if you want to optimize your aerodynamics as a cyclist, get a bike that allows you to get in the best position and, more importantly, that allows you to sustain it as long as possible.
