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.