Yesterday, as I rode down Pine Street in the rain, bouncing along at 20-25 MPH, my chain slipped off the chainring. All it took was a mixture of a little deferred maintenance, a chain drawing near the end of its useful life and the sorry condition of Seattle’s pavement following our January snows.
And it was no big deal. I braked, pulled onto the sidewalk, put the chain back and on and was on my way.
But if I’d been a slave to fixie fashion? Without brakes, I would have been absolutely screwed. The only way to stop a brakeless, chainless fixed gear bike going downhill is to lay it down or run into something. Chain derailment may be less common occurrence when riding fixed or single speed than it is with a geared bike, but it can easily happen.