Hop on a single speed bike and you'll notice it takes some pedal power to get it rolling. This is due to a mid-range gear ratio that works well for cruising on bike paths and streets. Single-speed mountain bikes have one ratio, but mountain terrain is far from consistent. This poses a question regarding the use of single-speed gears vs. multi-speed for mountain bikes, which is easily answered. Single-speed bikes allow the rider to keep both hands on the hand grips at all times.
Setups
Gear ratio is the relative diameter of the larger chainring sprocket and the smaller rear sprocket. With a standard 42-tooth chainring, a larger rear sprocket increases torque, while a smaller rear sprocket achieves more speed. A basic setup for courses with tight turns and sections that require torque might include a 42-tooth chainring with a 32-tooth rear sprocket. This produces a ratio of 1.5 to 1.0, which equates to one and one-half revolutions of the rear sprocket and rear wheel for each rotation of the pedals.
Hills
Climbing hills requires a gear ratio that allows the rider to maintain pedaling motion. In this regard, a 1.5 to 1.0 ratio would not be practical for the average set of legs. A more favorable ratio combines a 32-tooth chainring that turns faster, and a 17-tooth rear sprocket. Even though the 1.8 to 1.0 ratio appears opposite of the desired result, the faster chainring allows the rider to maintain momentum with a degree of power while climbing.
Roads
Any number of gear ratios may be suitable for mountain roads with subtle inclines. The particular setup would depend on the rider's preference and level of conditioning. A mid-range chainring and relatively smaller rear sprocket are typical applications where a greater average speed is desired. A setup using a 40-tooth chainring and 17-tooth rear sprocket combines for a 2.4 to 1.0 ratio. Some power is sacrificed at the start, but the faster rotation of the rear sprocket allows the rider to maintain a greater rate of speed.
Flip Flop Hubs
The latest in single-speed technology is the flip-flop rear hub. The hub has sprockets mounted on both sides and a rider can set it up so each sprocket produces a different ratio when combined with the chainring. Changing the gear ratio is as easy as flipping a quick release lever, pulling the rear wheel off the bike and turning it around in the dropouts. Experienced riders can do this in well under a minute, which is reasonably fast for a pit stop in most types of competition cycling.
Member Comments