UCI legal? That depends…

  • By Aaron Hersh and Nick Legan
  • Published Jan. 18, 2012
  • Updated Jan. 20, 2012 at 1:10 PM EDT
Dura-Ace Di2 adjustment box on the outside of the stem. Additionally, the Di2 battery is hidden inside the rear wheel cutout. Photo: Aaron Hersh

The innovation doesn’t end with the frame

Using a wind tunnel to design bike shapes by creating and testing prototypes before producing a final bike is now an industry-standard practice that Cervélo pioneered. After years of success with this strategy, they are changing the way they design bikes. Cervélo is going digital.

They have used computational fluid dynamics software to estimate aerodynamic drag for several years, but the quality and speed of their calculations has improved dramatically in the past year. As Cervélo co-founder Phil White describes it, “[CFD] is a math model that breaks the air into tiny little elements and understands what’s happening as each elements goes flowing by each other.” Basically, it’s a digital wind tunnel.

The shape of a wind tunnel influences the data it generates because the walls and ground influence airflow. CFD programs that don’t account for the interactions with the tunnel itself introduce another layer of uncertainty. Cervélo’s full time aerodynamicist designed programs that simulate the conditions in various tunnels and, with the corrections for each tunnel shape, Cervélo gained the confidence that their simulations produce accurate info. Their programs are now able to replicate data gathered in a wind tunnel to within 2-3%. White says the software still ranks shapes correctly, even if the numbers aren’t always identical to wind tunnel data. Testing shapes using CFD then validating that data in a physical wind tunnel allows them to experiment with more shapes and, therefore, design faster bikes.


The very first P5s will arrive in early March. These things are so scarce that the journalists at Cervélo’s launch event rode Caroline Steffen and Luc Van Lierde’s bikes. The complete P5 Tri (their name for the version with the triathlon fork) with Dura-Ace Di2 goes for $10,000. The frameset is $6,500. The road version is $6,000 with mechanical Dura-Ace and $4,500 as a frameset.

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