Why ride single speed?

"It allows an individual to really learn how to ride a bike...rather than just hang on and rely on ultra-low gears to bail him or her out climbing up the steeps," he says. "Momentum is your friend...with only a single gear, you really learn to let gravity help you carry speed into the next hill. Sometimes the gear you've selected will be much too large for certain climbs, so you have to really grunt it out and produce some power. Conversely, on the down-hills and flats, the same gear will be much too small and you'll have to spin the cranks super fast to keep some speed up. It's really, really cool to be the most important component on your bike! Single-speeding really augments that. Your mindset will determine whether it's fu n and challenging or hard and stupid." 

Matt Chester