| Features | Rear Wheel Cutout
Cervélo was the first to introduce a rear wheel cut out in a production frame. By shielding the spinning wheel from the wind, the cut out yields one of the largest single reductions in aerodynamic drag. The concept is inherently intuitive, however, executing the design requires true aerodynamic expertise.
In order to most effectively reduce drag, the cut out must have the right curvature and width to take full advantage of contemporary aerodynamic wheel technology. The result is that the wheel is completely shielded while maintaining its own aerodynamic advantages. We incorporate this knowledge on every Cervélo model with a rear wheel cut out.
On some Cervélos, the rear wheel cut out is extended upward to be even more effective; covering the top of the wheel is particularly important, as it moves forward at twice the riding speed. Yet even on Cervélos that don’t have this extended rear wheel coverage, the seat tube width and shape is engineered to be an aerodynamic match with the tire and wheel along the cut out’s entire height, even changing the seat tube’s cross section where necessary.
True Aero
In general, a good aero bike uses airfoil tube sections. This may seem obvious, but many “aero styled” bikes have arbitrary, “made-up” tube sections that can actually increase drag. In Cervélo’s early days, “aero sections” meant NACA (National Advisory Committee for Aeronautics) airfoils.
We still use some NACA foils where they make sense, but in our long quest to help Cervélo athletes go faster, we’ve spent enough time studying bicycle aerodynamics to not only design a family of our own aerodynamic sections (our TrueAeroTM library of airfoils) that improve on NACA for bicycle performance, now we’ve arrived at the next generation of aero design. We no longer design just a tube section (two-dimensional) – we now design entire bike frame skin surfaces (three-dimensional), taking into account the different air flow characteristic in each aero zone.
Smart Wall
Smartwall intelligently redistributes material around the tube cross section to increase lateral and torsional stiffness while adding the least weight. Smartwall was inspired by Cervélo’s aero bikes, whose shapes are driven primarily by low drag considerations. Reducing the frontal area of the frame is a part of an aerodynamically efficient design, but narrow tubes have inherent challenges when trying to construct a stiff and light frame. Smartwall addresses this elegantly.
Most unwanted frame flex is out of plane, putting one side in compression and the other side in tension. Thus, material farthest from the center plane has the greatest effect on improving stiffness. Smartwall adds material only at the outside walls, farthest from the center plane, to maximize lateral stiffness and minimize weight.
Smartwall clearly makes sense for all frames. In fact, we use Smartwall to set new standards in frame stiffness, strength and weight throughout the R series. And we still use Smartwall to create stiff and light aero frames. |
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