AERODYNAMICS FOR THE REAL WORLD
The Netherlands, home of FFWD Wheels, is world-renowned for its flat landscape, its rain, and its wind. These harsh conditions provide the world’s most rigorous testing grounds for carbon wheels. The FFWD team and it’s engineers have a significant understanding of real world wind conditions experienced by cyclists and how these conditions directly affect wheel aerodynamics and performance.
Due to this vast knowledge and the passion for innovation, FFWD initiated a project to develop a new aerodynamic rim profile. The initial concept was based on the theory that the effective real world winds experienced while cycling were in a lower yaw angle range than that of the 10-20° being cited and adopted by numerous competitors.
During the development phase numerous prototype rim shapes, widths and depths were produced and extensively tested. The result is FFWD’s proprietary DARC™ ‘Double Arc’ profile delivering true superior aerodynamic performance for the real world.
The proprietary DARC™ profile dramatically improves aerodynamics and handling by reducing drag in the most commonly encountered real world wind conditions with yaw angles of 0° to 10°.
The profile is designed to achieve optimal aerodynamic performance by reducing drag around the wheel in both frontal and cross wind conditions by creating a negative pressure section that compresses and speeds airflow over the rim’s positive section reducing drag while also increasing stability.
With the use of DARC™ in the F4, F6 and F9 series wheels the latest market trend of super-wide rims is not required and has shown to be less aerodynamic. FFWD has found that a rim width of 22.4mm in conjunction with the use of the DARC™ profile offers the best aerodynamics.
The DARC™ profile is designed and optimized for a 23mm tire width but allows for the use of a wide range of tire sizes from 19mm-33mm and is universally compatible with past, current and future frame models with no clearance or unique fit issues.
In early 2016, FFWD further confirmed the performance of the profile in the wind tunnel against a range of current leading competitor wheels. These results illustrate that DARC™ equipped wheel offers the best performance in real world wind conditions and can benefit a rider with time savings of 1 minute and 35 seconds over an Ironman™ distance bike leg.
Graph: 2016 F6R vs 2016 Zipp 404 Firecrest
Conclusion: Under real world conditions (average yaw angles less than 10°) that are most commonly experienced on the road, FFWD’s DARC profile wheels offer the best aerodynamic advantage over the leading competition.
Faster Wind Tunnel, SATP Drag Force (grams) versus Yaw Angle at 30mph/48.28kph
More recent studies in bicycle wheel aerodynamics have validated FFWD’s development premise of DARC™. Most notably the 2015 Catalyst Cycling LLC’s white paper “The Mathematical Model of Yaw Angle Distributions For Bicycle Wheels” (Zach McCormick, Nick McCormick, Justin Clarck).
Catalyst notes “that yaw angles between 0-10° will always be more prevalent than 10°-20° or between 20-30°.”
Even at the IronMan™ World Championships in Kona HI, according to Catalyst, “a rider spends 72.1% of the bike leg in yaw angles below 10°”.
Numerous wheel manufacturers claim that 50 to 80% of time will be spent experiencing yaw angles between 10° and 20° and have based their current wide rim profiles on this inaccurate premise.