Aerodynamics
Wind resistance is arguably one of cycling's biggest issues. With this in mind, we've made multiple trips to San Diego Low Speed Tunnel for testing and refinement of our wheel designs. In doing this, we've developed and confirmed world class, low aerodynamic drag for Mad Fiber wheels.
To summarize our findings:
(1) At zero degrees yaw and 30mph wind from straight-ahead, most top wheels are very similar. As long as spokes are minimal in number and profiled, and rims are aero, the drag numbers are tightly bunched. We find drag forces in the 120 to 150 gram range for all the top wheels, those with deep rims, minimal spoke number, and no serious aerodynamic flaws.
(2) As yaw increases, the order shuffles. With toroidal shapes, for example, drag gradually decreases, out to 15º, then steadily rises. The broad shape pays this benefit. For Mad Fiber, drag remains steady from 0º to 8º, rises from 8º to 10º, and then begins to decrease. At 15º, where all others are still increasing, Mads continue to drop. By 20º, the decrease steepens and they drop below any other spoked wheels. And this trend continues out to 30º, where our testing stopped.
For example, in late 2009, we tested a number of well known wheels. At 22.5º yaw, one of the best known samples generated 26% more drag than Mad Fiber. At 25º, its drag was 50% greater. At 30º, this competitor's drag was 109% greater, over double. Granted, these are extreme yaws, but this is what was measured.
Notes:
Magenta curve at top is a 27mm deep aluminum rim aero wheel with bladed steel spokes.
Light blue curve is a very well known and highly developed carbon rim aero wheel.
Orange curve is Mad Fiber.
Many variables in test protocol mean that results are intended to quantify factors that researchers are seeking. No test is directly applicable to real world situations.
Two questions arise:
(1) Why does the Mad Fiber wheel show such an improving trend from 15º to 30º? How does it manage to out pace all others, besides disk wheels, from 20º and on?
(2) What yaw angles are important? Some research suggests 10-20º is important. Others have asserted that 20º is the best all around indicator.
The "why" question is easy to answer, after the fact. Our spoke number is low, the spokes are short (due to a deep rim), and the shapes are simple (which results in less detached air).
As to yaw, we believe the wind angles that matter most are in the 20º range. Certainly, if stuck on the windward side of the peleton, you'd want a solution that delivers exceptional performance at higher yaws. And those who ride along coastlines or near open space are more subjected to wide wind yaw angles (Kona, anyone?).
NEXT: Brake Pads
