CycleOps

PowerTap G3/ZIPP 303 Firecrest Carbon Clincher Rear Wheel

CycleOps completely overhauled the design of previous PowerTap models, improving aspects ranging from rigidity to functionality. An 80-gram weight reduction from the popular SL+ makes the PowerTap G3 Rear Hub the lightest power meter in the world. CycleOps improved on the rigidity of previous models by shrinking the hub profile and widening the flanges. With the distractions of weight and stealth design out of the way, CycleOps improved the functionality and accuracy of data gathering. For one, CycleOps moved the orientation of the electronics that transmit user data to the end cap of the freehub body, making it possible to remove the electronics for service without swapping out the entire wheel. This means more time in the saddle and fewer headaches.

The new G3 is equipped with an ANT+ wireless transmitter that sends power, torque, speed, and virtual cadence data to CycleOps' Joule computer or any other unit that translates ANT+. Please note that the G3 is not compatible with Yellow CPUs. The G3 is capable of storing up to 15 hours of data in one-second intervals, and up to 30 hours of data in two-second intervals. The G3 design still has a 'torque tube' with eight strain gauges, yielding measurements accurate within +/- 1.5% between 40 and 130 rpm.

The Firecrest is Zipp's most ambitious rim shape to date. Designed to account for differences in airflow between tubulars and clinchers, the 303 Firecrest Carbon Clincher maintains a rim depth of 45.0mm and an aero width of 28.50mm. Using computational fluid dynamics, Zipp moved the center of pressure towards the steering axis to create the most stable and predictable deep-section rim on the planet. Zipp found that a wider rim offers greater vertical/lateral compliance for increased control, comfort, and rigidity. For the clincher, they found that moving the hook beads further apart allowed the tire to take on a more stable shape without adding rolling resistance. For the strength and rigidity, the Firecrest 303 utilizes uni-directional fibers to handle the tensile and comprehensive loading within the rim, and woven fibers in the spoke-hole areas. A woven silica-ceramic fabric and a woven carbon fabric encapsulate the braking and tire-mounting surfaces. The combination of fiber patterns creates the highest stiffness-to-weight ratio in Zipp production.

A number of Zipp technologies went into making the 303 Firecrest Carbon Clincher the most versatile wheel in the Zipp arsenal. First, the Multi-Material Co-Molding process permanently fuses a sub-200-gram aluminum hoop to a dimpled carbon structure that acts as a leaf spring for road vibration and impact. Spokes laced directly to the carbon body give you the benefit of a carbon feel and aluminum braking. Next, visco-elastic material is inserted between carbon laminate in the rim to reduce road vibration by ten percent. Lastly, the dimples of the Aerodynamic Boundary Layer Control (ABLC) on the curved rim section work to create a slight turbulence directly above the rim surface. This creates an artificial boundary layer that forces the laminar boundary layer towards the forward part of the rim to become turbulent. This process enables airflow to remain attached over more of the rim for a longer period of time, providing a lower level of integrated drag. The drag that ABLC creates is called skin friction drag; although it's greatly increased, pressure drag (which is ten times higher than skin friction) is decreased to make the 303 Firecrest wheels faster than the competition in a wide range of conditions, not just the wind tunnel. While most wheels only enjoy minimum drag at rarely occurring yaw angles of five and ten degrees, the 303 Firecrest experiences it at the real-world conditions of 10 to 20 degrees.