Follow the leader

Triathlon Forum
1

Warning! More musing below…

So Cervelo jumped way ahead in the arm’s race with aluminum P3 and then the P3C (now just called the P3), which has led to a spate of new bikes that claim to be/at least some data indicate are essentially just as aero, or at least very close. In alphabetical order, some of these are:

Blue Triad
Felt DA
Fuji D-6
Specialized Transition
Trek TTX (although it has been around longer than the other four, so I’m not sure you can argue that it was a response to the P3C…but anyway…)

Taking the above as a given, I think it is interesting to ask, what do these bikes have in common? The answer is that they all have cables that enter behind the stem, and except for the TTX they have all attempted to reduce the aero drag created by the rear brake (and seat stay/seat tube junction) either by relocating it under the bottom bracket (Blue, Felt, Specialized) or shielding it (Fuji). In addition, with the exception of the Specialized and perhaps the Fuji, they all have the downtube located close(r) to the front tire than is often the case (the Willier also deserves mention in this regard). Finally, the Specialized and the Trek have fork crowns/downtube junctions that are at least reportedly designed to smooth the air flow over this region, and the Specialized and Fuji have attempted to minimize the drag created by the front brake.

Put it all together, and it appears to me that these frames are achieving a drag close to that of the P3 by reducing the drag of various components, which compensates for their (again, apparently) less-than-optimal tube shapes.* That then raises another question: what would you get if you tried to improve upon the P3 by incorporating one or more of the above-described features? The answer to that, I think, is obvious: the P4…

*Of course, another interpretation could be that these features provide little or no benefit, and all of the bikes have similar drag due to similar tube shapes.

2

Warning! More musing below…

So Cervelo jumped way ahead in the arm’s race with aluminum P3 and then the P3C (now just called the P3), which has led to a spate of new bikes that claim to be/at least some data indicate are essentially just as aero, or at least very close. In alphabetical order, some of these are:

Blue Triad
Felt DA
Fuji D-6
Specialized Transition
Trek TTX (although it has been around longer than the other four, so I’m not sure you can argue that it was a response to the P3C…but anyway…)

Taking the above as a given, I think it is interesting to ask, what do these bikes have in common? The answer is that they all have cables that enter behind the stem, and except for the TTX they have all attempted to reduce the aero drag created by the rear brake (and seat stay/seat tube junction) either by relocating it under the bottom bracket (Blue, Felt, Specialized) or shielding it (Fuji). In addition, with the exception of the Specialized and perhaps the Fuji, they all have the downtube located close(r) to the front tire than is often the case (the Willier also deserves mention in this regard). Finally, the Specialized and the Trek have fork crowns/downtube junctions that are at least reportedly designed to smooth the air flow over this region, and the Specialized and Fuji have attempted to minimize the drag created by the front brake.

Put it all together, and it appears to me that these frames are achieving a drag close to that of the P3 by reducing the drag of various components, which compensates for their (again, apparently) less-than-optimal tube shapes.* That then raises another question: what would you get if you tried to improve upon the P3 by incorporating one or more of the above-described features? The answer to that, I think, is obvious: the P4…

*Of course, another interpretation could be that these features provide little or no benefit, and all of the bikes have similar drag due to similar tube shapes.

AC,

I think you are right about your observation to some degree. Some bikes are fast in spite of their tube shapes.

I think that the low drag numbers on the P3 are impressive given their cable location. There is a challenge to proprietary components like frame-specific forks or brakes or stems or hubs or headsets or handlebars. Overcoming these challenges within the UCI rules will be the next hurdle to overcome and may very well leave smaller companies behind that don’t have the ability to create their own integrated systems.

While the P4 is a step toward this integration of systems, I wonder how much faster it would/could be if the headtube and its shape were revised to use the same narrow hourglass/nosecone shape, but 1" headset bearings? I mean if the Look or GT SBII is stiff enough with steerer tubes 80% smaller that 1" why have any part of the head tube 45mm wide, even if it is only the bearing seat? Same with BB shell width or front and rear O.L.D.; the UCI doesn’t care about those areas, Gary was onto something methinks.

-SD