Cancellara vindicated by video analysis

If you watched any of the spring classics this year, you saw incredible performances by Fabian Cancellara, including a few stunning attacks. Apparently there has been speculation that he used some sort of seat post-embedded electric motor.

Were Cancellara's decisive accelerations even humanly possible? How much power did he generate when he hammered the field at Paris-Roubaix?

Physics to the rescue! (Don't get to say that often enough.) The link takes you to an excellent post at Cozy Beehive where video analysis is used to determine Cancellara's speed, acceleration, and power output. There's also a clip of the race in case you missed it. For the sort attention set: the analysis suggests his move required over 1000 Watts during the attack. Humanly possible, but incredible.

Rocks are punier at 9/10ths scale

In physics we have the idea of scale invariance. Here's how it applies to mountain bikes: You can think of 29" wheels as 10/9ths the diameter of 26" wheels, but you can just as well think of the wheels as the same size but the 29er sees all the rocks at 9/10ths scale. So that means the terrain is about 10% smoother on 29" wheels. Of course, on the trail, additional factors affect ride quality (wheel flex, geometry, suspension, etc.), but wheel size matters.

The 29er wheel is larger than the 26, but the step is the same size:

Equivalently, the wheels are the same size and the 29er rides over a world that's 9/10ths as big:

Pulling ahead on downhills: pedal before resting

A downhill after a climb is a great place to recover. But if you're racing to the bottom, it's better to pedal past the top before easing up. The video after the jump demonstrates this in a very controlled setting, with two carts rolling down a pair of smooth ramps - analogous to cyclists coasting down a smooth hill.