The fastest wheels that also just happen to be the best performing!
So how are they so good?
PCW Engineers designed the sinusoidal shape to reduce vortex shedding, a phenomenon which occurs when air travels across a bluff, creating alternating low pressure zones behind the object (in the case of a bicycle wheel, the object is the tire and the leading edge of the rotating rim).
By moulding the rims into a shape with 24 oscillating sinusoids, they are streamlining the air flow, allowing the spokes, hub, trailing edge of the front wheels, as well the frame, rider's legs and feet, and rear wheel system to flow through the air with less drag and more stability.
As it relates to aerodynamics and stability, PCW definitely nailed this.
What PCW didn't expect and are very pleasantly surprised about is what the sinusoidal shape does for the strength and stiffness of the wheel. By mounting each spoke to the most convex part of 24 sinusoids, they are putting the carbon under maximum tension (almost 4800 pounds of force for each wheel), There has never been a stronger wheel, The strength that the shape provides allows to lay the wheels up with less carbon in some areas and more carbon in others, thus allowing the wheels to be lighter.
When you combine the aerodynamic and stabilizing effect, as well as the strengthening and stiffening effect of the sinusoidal shape, together with the lighter rim, you get an overall wheel system with truly unique performance characteristics across the entire spectrum of profiles and terrain as well as wind conditions.
Optimized layup and advanced mechanical design means material can be removed where not needed and applied only where necessary. The result is a medium-deep section rim that is lighter than many shallower depth traditional carbon wheels.
Profile Depth (mm, avg)
Zipp 454 NSW
Zipp 404 Firecrest
Performed at A2 Wind tunnel using exacting protocol. Continental GP4000 SII tires were chosen because of wide use in both application and testing. Tires were inflated to 100psi and double checked before each run. 0-20 degrees of yaw at 2.5 degree intervals. Interval value is the average of 2 time stamped data collections at each yaw position. Wind speed of 30mph. These controls have been used for dozens of cycling product manufacturers, including brands tested against.
Nipple placement at a convex point puts carbon naturally into tension as opposed to every other wheel where internal edge concavity means the carbon is in compression. Stress levels remain more uniform across the entire rim body as a result, creating a stiffer, more responsive, and overall stronger wheel.
Finite Element Analysis show superior uniformity in regards to stress migration from the spoke point through the foil body out to the rim hoop.