Cadence staff and clients may not all agree on what products they prefer to use, but the one thing that we all agree on is that the products Cadence sells get our blood racing. If you're a passionate cyclist or triathlete you can always count on Cadence having stock of the best, rarest, most testing, and most exotic equipment. And no less for Cadence staff than for our customers, coming into Cadence everyday is like being children arriving at the hallowed halls of FAO Schwartz for the very first time.
One of the brands that gets us really buzzing is Zipp. And for very good reason. In Zipp's relatively short lifespan making super fast, super light, and super strong bike racing wheels they've turned the industry on its head. Who can remember a deep dish carbon road racing wheel prior to Zipp? Who can remember a readily available sub-1300 gram wheelset prior to Zipp? Sure, Olympians and national teams had crazy carbon wheelsets and discs by Paul Lew and maybe Steve Hed--and Jan Ullrich had his crazy light Obermeyers--but the weekend warrior was still out there on his Mavic GP4s.
Today Zipp engineers what are arguably the fastest wheels available to pros and amateurs alike. And Zipp doesn't just claim that their wheels are aero and advantageous; they spend countless hours in San Diego's low-speed wind tunnel refining their products to verify and quantify just how aerodymanic and how advantageous their wheelsets truly are. These hours in the wind tunnel also tell Zipp where and how they can improve the aerodynamic profile of their products, and this results in a process of continual refinement and improvement.
The most recent generation of Zipp aero wheels take full advantage of Zipp's patented 'bulging' rim profile, or aerodynamic boundary layer control (ABLC) technology. Wind tunnel testing has shown that deep dish or so-called V-section rim shapes can only improve aerodynamic penetration if the air is actually adhering to the surface of the rim. With a V-section or flat-sided rim airflow gets separated from the rim which creates a vacuum trailing the rim: this is the primary source of aerodynamic drag.
With Zipp's ABLC curved section rim the airflow adheres to the rim to a much greater degree than with a simple V-section; but with greater yaw (wind angles in excess of 8 degrees) the airflow still begins to stall. Hence the introduction of Zipp's notorious dimpling: the dimples actually force the airflow into a higher energy state which forms a turbulent boundary layer near the surface of the rim, which allows the air to remain attached to the rim even at higher angles.
Whereas most aerodynamic rims show minimum drag at between 5 and 10 degrees in the wind tunnel (conditions only seen 20-25% of the time in the real world) and then show increasing drag through higher wind angles, the ABLC allows the minimum drag to occur between 10 and 20 degrees. Because about 50% of real world riding occurs with effective wind angles between 10 and 20 degrees Zipp's design is a wheel that is not just faster in one condition, but faster through the range of conditions you will experience the majority of the time.
While aerodynamic penetration is at the heart of Zipp's wheel development program, they certainly don't rest on the improvements they can make in just that arena. Zipp worries about weight, rolling resistance, strength, spoke quality and design, and numerous other factors that the uninitiated would never think about. After all, we just want to ride fast wheels and be reassured that they are indeed fast. With Zipp, you can be certain.