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UCI legal? That depends…

  • By Aaron Hersh and Nick Legan
  • Published Jan. 18, 2012
  • Updated 18 hours ago
The Cervelo P5 with the triathlon fork. Photo: Aaron Hersh


Anytime a big player in the aero bicycle market launches a new bike, it’s a big deal. In the case of Cervélo’s P5, it was a slightly bigger deal than any other launch in recent history. Why? Well, not only was the cycling press waiting to see the latest wind-cheating design from the Canadian manufacturer, but there were rumors of hydraulic brakes, something not entirely new, but certainly interesting.

It turns out that Cervélo appears to have delivered once again on a bike that is not only aesthetically pleasing, but also functionally compelling. Cervélo partnered with both Magura and 3T for the P5. And the result is a fine example of the increasingly popular trend of frame and component design integration.

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Playing with the rules, and winning

The frame is UCI legal and one iteration of the new fork is as well. Cervélo also offers a triathlon-specific fork that is not. The frame conforms to the regulations stating that tubes must be no more than three times deeper than their width, but Cervélo used a loophole to stretch the seat tube beyond the typical interpretation of the rule.

Cervélo senior advanced R & D engineer Damon Rinard says the UCI allows “gussets” that support and connect the frame tubes as long as they are no deeper than the original tube dimension. The P5’s seat tube is 27mm wide, which means it must be 81mm or shorter in the longest direction, and the seat tube is almost exactly that length. The gusset connecting the seat tube and the top tube, however, is another 81mm.

These connected elements create a surface that is 162mm at its longest point. A second gusset is used to connect the seat stays to the seat tube that extends the segment of the tube deeper than the UCI’s 3:1 ratio lower on the seat tube. At its widest point, the P5 actually has a 6:1 ratio, yet it still abides by the UCI’s 3:1 rule. Go figure.

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