Bicycles with multiple gear ratios give different riders the ability to find the one that's best for their particular budget and riding style. Bicycles with multiple speeds use a derailleur for the chainring or cassette to lift the chain and shift between higher and lower gears, which provides either higher or lower torque. Single-speed bicycles eschew this variation for simplicity, weight savings and lower cost.
One Speed to Rule Them All
A single-speed bicycle is one of the simplest designs in cycling. These bicycles are simple and elegant, and use a chainring and a single gear to provide a set level of mechanical advantage for the rider. Single-speed bicycles are ideal for areas that are consistently flat, since they cannot be shifted to a lower gear on an incline. Some single-speed bicycles have a fixed gear in the back, which makes the pedals rotate any time the bike is moving. Other single speed bicycles use a flywheel to allow the rider to coast without the pedals moving.
More Speeds, Fewer Problems
Multiple-geared bicycles use several gears of different sizes on the front chainring and rear cassette. On inclines, you can shift to a lower gear that requires less torque to slowly ascend the hill. Increasing the gear ratio increases the torque, allowing for higher speeds on flat areas or steep descents. This variation in speeds is provided by a combination of a front and rear derailleur, which lifts and aligns the chain with a different set of gears using a steel cable. The entire drivetrain is more complex and heavier than a single-speed bicycle, but multiple gears make the bike more suitable for varying terrain.
Single-speed bicycles are often less expensive and require less maintenance to keep running smoothly, making them popular for long-distance mountain bike touring. The simplicity of a single speed makes it ideal for mountain bikers who might be stranded far from civilization if an errant rock breaks their derailleur. Single speeds are also ideal for urban commuters, since most cities are relatively level, eliminating the need for multiple gear ratios. Multiple-geared bikes have a clear advantage when hills are expected, and the efficiency of different gears is unparalleled. This makes them ubiquitous for most competition mountain bikes, racing bikes and touring bikes.
Choosing A Bike
Casual riders may gravitate toward single speeds, since the stripped-down function of these bicycles is extremely reliable and ideal for rides around town. Cruiser and comfort bicycles often come in a single speed. Multiple-geared bicycles are usually preferable for most riders, since the low gears make conquering hills much easier and more efficient. Multiple geared bicycles have a bit of a learning curve and require periodic adjustment to keep running with precision, but the negatives are worth the ability to take on more difficult rides for a better workout.
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