Can anyone explain the physics of Hesjedal's bike...

[Lister Farrar]

...after his crash? Why does it speed up after it stops? Looks like the camera moto driver didn't expect it either.
http://www.steephill.tv/players/youtube ... kk&yr=2014

[EricS]

I think it comes to a near stop while still connected to Ryder's shoe, then after he releases, the bike is free to move. The centre of mass of the bike doesn't move very quickly, but for some reason (slope and wheel positions?) the bike rotates around and under the wheels of the motorbike. Very interesting.

[Robgrant]

I think the rear wheel is still rotating when he crashes and when it touches the road it drives the bike around while it pivots on the front wheel. That or there is an invisible motor attached to the Di2 battery. Let the conspiracy theories begin.

[Rolf]

I agree it appears his rear wheel was still spinning. There was insufficient friction between the side of the wheel and the road once the bike was on the ground to slow down the rotation. The whole clip is in slow-mo, which skews our impression of how things should move. The sliding motion certainly gives the impression of an ice rink.

From this Velonews article:

Roads in southern Spain are covered in dust, grime, and oil, baking under an intense sun without rain for weeks if not months.

“The roads were pretty treacherous out there,” he said. “We were managing it pretty well, but my bike just slipped out from underneath me.”

[Fozzy]

Perhaps he chose the wrong line rather than the wrong path

[Mickfly]

My theory is that he fell because the road was super slippery. The road surface is dry but polished. If you watch the clip the finishing frame shows the sun reflecting of what looks like a polished pebbly surface.

Thats why he falls!

Why the bike appears to move after it seems to stop is because the road is cambered to the left (inside of the turn). The rear wheel simply rotates/rolls down the hill, pivoting on the pedal.

Then 2 fatties on a motorbike run over it.

Mick

[John D]

Apparently some news outlet reported that the wacky behaviour of Ryder's wheel was evidence that he had a motor assist! His reaction is pretty funny.

http://sporten.tv2.dk/2014-09-04-hesjed ... latterlige

[Mickfly]

Oh well. I'm wrong.

He needs to loosen up a little tho!

[JohnT]

"Spinning things do weird things when they fall down" That's all ya had to say.

Instead: "This is how 'assist' works, therefore it's silly that people are making this claim when my cranks are clearly not moving." Ya, that makes us all feel a lot better.

JT