I normally hand pan shoot these a lot slower (1/160s) however 1/640s at the speed these guys go is about the maximum and still get some blur in the wheels and the BG. It is very technical and you need lots of practice to get it right. There are no second chances.
High Quality Image here. 800px is just a waste of time. It's too easy to hide flaws in 800px and it's archaic and self-defeating for a photo-competition site.
Here's an outtake:
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