Originally Posted by
tashi
Although it's kinda mean fun to watch you try to figure it out, I'll step in here:
When your wheel turns backwards, the freewheel engages, causing the cranks to turn. If you don't pedal backwards when traveling backwards, you'll apply forward force to the cranks, and your bike will stop. Freewheels can only "freewheel" one direction, otherwise you wouldn't be able to apply force to the rear wheel.
Ahhhh....but you guys don't know about Freecoasters.
http://en.wikipedia.org/wiki/Freecoasters
"A freecoaster is a bicycle hub that can rotate in either direction without the pedals moving; most designs incorporate an adjustable-slack clutch mechanism that engages or disengages by pedaling or backpedaling, respectively. It has become a more common item in freestyle BMX, and enables the rider to go backwards without having to backpedal."
Most BMX flatland bikes have these.
Here's how you use it:
http://www.youtube.com/watch?v=8U4_C4RQUC0