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4 June 2006

2006 Zipp 808 Tubular

Think back to David Zabriskie's trouncing of Lance Armstrong in the 2005 Tour de France prologue. Remember those spectacular wheels Zabriskie was using? Yeah, those were Zipp 808 wheels. The 808s are the latest in groundbreaking wheel development technology from the American-based company. They are crazy light, very sexy and, as it turns out, legal in all race applications from time trials to triathlons to track to road races.

 

She Blinded Me with Bulges and Science

The R & D boys down at Zipp are a heady bunch and it shows in the 808s. They utilize some of the most forward-thinking engineering ever seen in wheels. The essence of the 808 wheelset is Zipp's patented ABLC technology (Aerodynamic Boundary Layer Control). Look at the profile of the 808 and you'll notice that it has a peculiar bulging profile to it. It's not V shaped or flat-sided like most rims. The reason for this is that the bulging rim profile allows air to stick to the surface of the rim and thus fully exploit the benefits of the airflow against the wheel. When airflow is a couple of degrees off center, rims with a V shape or flat side get separated from the airflow thus creating pressure drag on the wheel.

It's All in the Dimples

What it all boils down to is that the less turbulence an object creates as it passes through air the faster it will go, with less energy expended to make it move. Look at the surface of the Zipp 808s and you'll notice little dimples much like a golf ball. Why are they there?

The Zipp engineers again have a good answer. Simple logic just doesn't "get it." It turns out that the dimples on a golf ball are there to generate turbulence, which in turn causes a high Reynolds number (see www.reference.com/browse/columbia/Rynldsnum for definition) and pressure drag reduction. The pressure drag reduction created as a result of the dimples is some ten-times less than the friction drag created by the bulging rim profile. In the case of the 808s, the added dimples also create a turbulent boundary layer near the surface of the rim, which allows the air to stay next to the surface of the rim with minimal disturbance as it passes through air. Wind rarely blows in favor of the cyclist, but the dimples keep the air turbulence near the surface of the rim even when wind angles range from 10 to 20 degrees, the wind conditions most often encountered by cyclists.

The Ride

My fellow BiciRace.com mate, who was with me on the ride, was literally left gasping for air as I accelerated on the flats. - Zipp 808s

All this science is well and good, but how do the Zipp 808s perform? After having the Vittoria Corsa Evo CX tubulars properly glued to the wheels by my homeboys down at Sellwood Cycles in Portland, Oregon, the 808s were ready for action. Bear in mind these wheels were not tested under the conditions in which the 808s excel most: time trials, triathlons and track racing. My fellow BiciRace.com mate, who was with me on the ride, was literally left gasping for air as I accelerated on the flats. The acceleration of these wheels is that astonishing! It was a rather blustery day with a strong crosswind and the 808s handled the conditions beautifully just as Zipp said they would. Even without the benefits of an echelon, using the 808s I was motoring through the crosswind with noticeably less energy expended than on my box-rimmed wheels.

I was told by several respected bike mechanics that regular break pads can be used on carbon fiber wheels, as long as the same pads are not shared between alloy and carbon rims. The metal on alloy wheels has been known to flake off on the pad, which can be very hazardous to the silica breaking surface of these wheels. Zipp, however, recommends you use a special break pads designed specifically for carbon fiber wheels. The composition of these break pads help to mitigate the heat generated as the wheels roll and to prevent premature wear.

Details:
•  Wheel weight: 1395g tubular, 1775g clincher version
•  Available in both clincher and tubular, 700c only
•  Easily changeable freehub for Shimano or Campagnolo
•  Sapim spokes: 18 on the front, 24 in the rear
•  81mm depth
•  Skewers not included
•  Price: about $1,955 USD

Visit the Zipp Speed Weaponry website to learn more about the 808 wheels and the rest of their innovative products.

Review: 2006 Zipp 303 Clinchers, 4 May