Singlespeed

A single-speed bicycle is a type of bicycle with a single gear ratio. These bicycles are without derailleur gears, hub gearing or other methods for varying the gear ratio of the bicycle.

There are many types of modern single speed bicycles; BMX bicycles, most bicycles designed for children, cruiser type bicycles, classic commuter bicycles, unicycles, bicycles designed for track racing, fixed-gear road bicycles, and single-speed mountain bikes.

The fixed-gear single-speed bicycle is the most basic type of bicycle. A fixed-gear bike does not have a freewheel mechanism to allow coasting.

A single-speed bicycle is generally cheaper, lighter, and mechanically simpler than its multi-geared equivalent. Without derailleurs or other gearing systems, there are fewer parts on the bicycle that require maintenance, making this type of cycle useful for city commuting in all weather. The drivetrain efficiency of a single-speed can be greater than today's typical multi-geared bicycles. A straight chainline, lack of chain drag from rear derailleur jockey pulleys, and lack of chainrings, ramps and pins all improve efficiency. As a single rear cog takes less space than the typical seven to ten cogs present on most multi-geared rear cassettes, rear wheels can be built with little or no dish.

As the single-speed bicycle lacks alternative gearing ratios, it is less versatile, as it cannot be pedaled efficiently outside of its single gearing range. Without lower gearing options, the single speed bicycle is generally more difficult to pedal uphill. Conversely, its dedicated gear ratio also limits top speed, and is slower than a multi-geared bicycle on flat or descending terrain once bicycle speed exceeds the rider's ability to maintain continuing increases in cadence (pedaling revolutions per minute), typically 85–110 rpm.

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