Cogset

On a bicycle, the cassette or cluster[1] is the set of multiple sprockets that attaches to the hub on the rear wheel.

A cogset works with a rear derailleur to provide multiple gear ratios to the rider.

Although cassettes and freewheels perform the same function and look almost the same when installed, they have important mechanical differences and are not interchangeable.

The British Cycle Engineers Institute (CEI) thread was adopted as the international standard[when?]

The major disadvantage of the multiple sprocket freewheel design is that the drive-side bearing is located inboard of the freewheel, and as sprockets were added over time, the bearing moved inward, farther from the drive-side axle support.

Multiple speed freewheels were common on quality high end bikes until the late 1980s.

[3] Suntour — Maeda Industries (Japan) introduced a compact 6 speed freewheel which reduced the spacing between the sprockets and was the same width as a standard 5 speed freewheel but required a narrower chain than the standard.

The concept was copied by European freewheel manufacturers Regina (Italy) and Maillard (France).

Some new single-speed — especially BMX and utility bikes — and lower-end multi-geared bicycles continue to be manufactured and sold with freewheels.

Since their introduction in the late 1970s[6] cassettes have been used on increasing numbers of bicycles, starting at the high-end and over time becoming available on less expensive bikes.

Over time, the number of sprockets in a cogset has increased, from 3 or 4 before World War II, to 5 used from the 1950s to the 1970s, up to the 8, 9, 10, 11, 12, and even 13 in the 2010s [when?]

This results in functionally compatible shifters, but specific freehub bodies, or necessitating the use of a spacer with a 7-speed cassette on an 8-speed hub.