Trek Madone Review

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Nice stuff, but what pushes the new bike to the forefront of road bike design is aerodynamic efficiency. It isn’t the first or the only road racing cycle designed to pass more easily through the air than one that isn’t, well, “aero” but it is a breakthrough design for Trek.

The aerodynamic treatment borrows from the phenomenon behind the firm’s Speed Concept time trial frame; identified

Flat back of the KVF downtube

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prior to the second world war by German aerodynamicist Wunibald Kamm, it is that air flows around a truncated teardrop shape in almost the same way as it does around a full teardrop. “Truncated” means that part of the tail of the teardrop is missing; classically, the cut should be made at the point where the tail has tapered to 50percent of the maximum cross section. Do so and the air passing

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along the sides of the teardrop continues its travel almost as if the tail were still in place. In other words, a truncated teardrop is almost as effective at parting the air as a complete one. Almost; the complete teardrop creates less drag. However, a full-length shape is long. This makes it unwieldy if used in a car and it was in car design that the so-called Kamm tail made its mark.

Turn to bicycles, and the Kamm shape offers a way around another difficulty. UCI regulations forbid the use of an aero shape with chord (length) to thickness ratio of 3:1. This is too fat to work as a teardrop, but take a 5:1 airfoil (which is not) and cut off the last 20percent of its length, as Trek did with the Speed Concept, and you have a shape that meets UCI demands while offering a drag figure way below that of a 3:1 lemon pip.

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