Zipp’s amazing Firecrest rim is more aerodynamic than any other, plus it improves handling in crosswinds, wheel strength, and overall ride quality. Here’s how:
More speed Previous rim shapes were designed to smooth airflow coming off the tire, and tapered inward from the widest point of a toroidal bulge. Zipp’s Firecrest rims have a less pronounced bulge and maintain a near-constant width almost all the way to the spoke bed. Without giving up the proven benefits of the toroidal shape, Firecrest is the first aero profile that effectively controls airflow around the back half of the wheel.
The benefits are substantial. With Firecrest, the latest Zipp 404 Tubular (58mm rim depth) matches the aerodynamics of the pre-Firecrest 808 (81mm depth). And the new 808 Tubular is faster than any competitor’s 90mm rim.
More stability Using computational fluid dynamics (CFD), Zipp discovered subtle variations in rim shape that improve stability without increasing aerodynamic drag. By moving the center of pressure (the focal point of side forces on the rim) to its optimal location near the steering axis, Firecrest rims offer stable, predictable handling at every wind angle. In real-world conditions, Firecrest rims are markedly more stable than other rims of equal or even shallower depth.
More control, comfort and strength, too Firecrest rims are also wider, which increases lateral stiffness for sprinting and cornering, and offers greater vertical compliance for more control, comfort, and durability, without adding rolling resistance.