Cassettes & Chains

The term “cassette” refers to the entire set of sprockets mounted on the freewheel hub, also known as the cassette body of the rear wheel. Cassettes may consist of anywhere from 7 to 10 sprockets. Because cassettes are controlled by the rear derailleur, they define a bicycle's final gear ratio. The cassette helps with the fine gradation of the gears, as opposed to the chain rings in front which select the approximate level (easy/moderate/difficult). The individual sprockets are identified according to their teeth. Standard increments consists of 11 to 32 or 34 teeth, whereby sprockets with few teeth allow for shifting into difficult gears, and sprockets with many teeth are identified as easier gears. Additional increments are common for racing bikes and tend to allow the bike to reach higher speeds. The choice of chain depends on the number of sprockets in a cassette. For example, a 9-speed cassette cannot be used with an 8-speed chain, because the chain would be simply too wide for the narrow spaces between the sprockets. Because they are responsible for the efficient transfer of the cyclist's pedalling force to the rear wheel, chains require regular maintenance and should be oiled regularly to prevent them from wearing out and causing other drive components to wear out more quickly as well.