It's no mystery why Zipp dominates the high-end wheel market. Their commitment to innovation is unmatched, and their engineering is flat-out brilliant. Using techniques and materials utilized by the aerospace industry, Zipp goes beyond the limitations of conventional carbon fiber hollow molding. When Zipp introduced their Inversion Composite Technology (ICT) rims in 2001, the praise couldn't have been louder or clearer. No dissension could be found: never before had a wheelset been so light, so reliable, so flat-out fast. Combine this critical response with a litany of impressive race results (who could forget Rik Verbrugge riding Zipp 909's to his victory in the 2001 Giro d'Italia Prologue at an average speed of 36.5mph?), Zipp had every excuse for resting on their laurels. But in typical fashion, Zipp kept bullying the limits of performance. In 2002 they set the new standard for clincher rim performance with m2cm co-molding technology, they manufactured the lightest, most-precise hubset in the industry, and they released the lightest wheelset ever made -- the 960g Z3 303 tubular wheelset. For 2003 the innovation didn't let up. Zipp unveiled their new Aerodynamic Boundary Layer Control disc wheel skins to make the world's fastest wheel even faster. And their VcLc technology improves the ride quality and overall performance of their 303 and 404 wheelsets.
The basic construction of Zipp's rims has remained the same for 2003. Using ICT, their rims are built with a continuous band of unbroken radial fibers. This radial monocoque forms the structural core of the wheel, and is responsible for not only an increase in lateral stiffness (20% greater than any other wheel made), but also affords a significant increase in strength and reduction of weight over any other wheelset. These purely radial fibers form the basis for Zipp's highly directional fiber system, which orients fibers in key directions relative to the radial layer of fiber. In fact, fiber orientation is so specific that woven fabric is used exclusively in load-bearing area such as the spoke nipple seat. This woven fiber combats high stress due to rim drilling, and significantly increases toughness and durability with no weight penalty. Zipp uses ICT to manufacture rims in 38mm, 40mm, and 58mm depths. These rims are the backbone of the premier wheelsets money can buy: the 303 Mid-V, the 404 Deep-V, and the 909 disc.
Zipp learned unexpected lessons during the R&D of the ICT process. It appeared that different laminate designs yielded varying lateral stiffness measurements and differing vertical compliance and resonant frequencies within identical rim shapes. Zipp took this data and worked in conjunction with the 3M Advanced Polymers Division to harness these laminate properties. By specifically placing constrained visco-elastic elements within the carbon laminate, it allows the rim to filter out high-frequency road shock while remaining equally laterally stiff. In short, under heavy vertical loads and deflection the constrained layer actually becomes slightly displaced by the carbon sidewalls, utilizing its viscous properties to rapidly spread out shock loads while dissipating large inputs into fractional amounts of heat. This new VcLc rim is half the weight and has twice the stiffness of an aluminum rim, but it has a dramatically lower natural frequency when subjected to vertical inputs. Beyond this increase in comfort, the rim improves cornering efficiency by allowing the tire contact patch to remain more consistent over varying road conditions. Zipp's research also proved that this contact patch consistency decreases rolling resistance.
There's more to the Zipp story than just ICT and VcLc. All Zipp rims feature a regenerative airfoil shape -- the classic bulge in the sidewall of the rim. This shape is so special because it utilizes the airflow as it separates off the surface of the tire and reintegrates the air back into the flow. The result is that incoming airflow "sees" the rim and tire as being smoother and more curved than it actually is. The separated airflow forms a bubble around which incoming air flows, allowing the Zipp rim to gently curve into an optimized trailing edge resulting in the smallest turbulent wake and lowest drag of any deep-section rim. You'll also experience a reduction in crosswind drag as the flow circulates around the body more easily.