Tech Talk with Lennard Zinn
At the Giro d’Italia, I found a number of new aerodynamic bikes of interest to triathletes:
Iker Camaño Ortuzar’s Saunier Duval Scott Plasma’s rear brake caliper may be hidden from the wind better behind the horizontal platform atop the seatstays than a rear brake caliper that is hidden from view (but not from the wind) under the bottom bracket would be.
The Plasma’s chainstays are horizontal for two-thirds of their length before angling steeply upward to the rear-entry dropouts, and the junction of the down tube and seat tube is raised and leveled to avoid creating a little vortex in the crotch of the tube intersection. A fairing extends downward around the rear wheel behind and below the bottom bracket.
The trailing edge of the fork crown fits tightly into a notch in the underside of the down tube to allow air to pass smoothly by that area.
The Plasma’s integrated seat mast is fitted with a slip-over Ritchey saddle clamp that allows substantial vertical adjustment without shims and has many centimeters of fore-aft adjustability along a hexagonal-cross-section track. As the single clamp bolt pulls the clamp ears against the rails from the side (squeezing them against an inboard stop), the lower lips of the clamp ears follow a tapered surface to pull the clamp down against the rails.
Robbie McEwen’s Ridley Dean time trial bike features Ridley’s R-Flow jetfoils on the fork and seatstays, a variation on Oval Concepts Jetstream fork. Both the stays and the fork feature split aero blades with a new shape designed by MIT aerodynamics guru Mark Drela. The rear brake is hidden from view behind the chainrings under the bottom bracket but exposed to wind under there, but in the future, a little fairing for the brake will be molded in under there.
The Dean’s fork and stays are not only aerodynamic themselves, but their split blades also suck air away from the spokes and reduce the aerodynamic drag of each wheel.
The Dean’s fork blades and seatstays curve in to come closer to the wheel to further cut drag. A special molding process results in very sharp trailing edges of the jetfoils.
The Dean’s shallow head angle gives stability at speed. It has a consistent seat tube angle in line with the bottom bracket; three seat angles are available: 73.5, 76, and 78.5 degrees.
The Oval low-profile front brake is hidden behind the fork crown, and the recessed brake-bolt nut on the front of the fork crown is hidden under the base of the head tube.
The Dean’s aero integrated seatpost has a slip-over saddle clamp to maximize vertical adjustment, and it has a long track for horizontal adjustability, but rather than clamping to the track, it requires multiple threaded holes for the vertical bolt.
Bianchi has really stepped up its time trial bikes, giving Barloworld a powerful tool for races against the clock. The precise seat tube cutout, deep aero seat tube, down tube and fork, and smoothed head tube trailing edge are big improvements complementing components like the FSA NeoPro crank with solid carbon chainring, and the Vision aero bar and brake levers.
Bianchi’s Reparto Corse (Racing Department) was once legendary both for quality and style of bikes for its racers, like, in this case, Swiss rider Patrick Calcagni. I’m not sure what the reason would be for this big chainstay cutout, but it sure looks cool.
Bianchi’s new integrated seat tube cap/saddle clamp offers ample fore-aft and height adjustment. Its clamp can hold the oval-cross-section braided carbon rails of this Fizik Aliante saddle without interchanging clamp parts.
Bianchi’s duck-beak aero trailing edges to the fork crown offer a unique way to access the brake bolt on a deep aero fork.
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Technical writer Lennard Zinn is a frame builder (zinncycles.com), a former U.S. national team rider and author of numerous books on bikes and bike maintenance including Zinn and the Art of Triathlon Bikes and the pair of successful maintenance guides Zinn and the Art of Mountain Bike Maintenance – now available also on DVD, and Zinn and the Art of Road Bike Maintenance, as well as Zinn's Maintenance Tips and Skill Building for Cyclists.
Zinn's regular column is devoted to addressing readers' technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions DIRECTLY TO ZINN. Zinn's column appears here each Thursday.
