Small wheel bicycles are adult bicycles which have wheels of 20 inch (51 cm) nominal diameter or less, which is smaller than the 26" size common on many full-size adult bikes, especially mountain bikes. While many folding bicycles are small wheel bicycles, not all small wheel bicycles can fold. Some small wheel bicycles neither fold nor separate, such as the Moulton, which comes in both fixed frame and separable frame versions. While BMX bikes also have 20" wheels, they are not normally categorised as 'small wheel bikes'.
For general information on small wheel folding bikes, please refer to the Folding bicycle article. For specific manufacturers, follow the categories links.
An early proponent of small-wheeled adult bicycles was Alex Moulton who pioneered the field with his F-framed Moulton Bicycle in 1962. His original small-wheeled design notably featured full suspension. Raleigh introduced the RSW-16 as a direct competitor, but it lacked the suspension of the Moulton, and compensated for this by using very wide 2-inch "balloon" tyres. The RSW-16 "Compact" was a folding version. In 1968 Raleigh introduced the Raleigh Twenty which later went on to become one of Raleigh's biggest sellers. A large number of European manufacturers made U-frame small-wheeled and folding bicycles in the 1970s.
Advantages and disadvantagesEdit
Smaller wheels are more maneuverable. For the latter reason, and in some cases for comic effect, they are used in some clown bicycles. Smaller wheels more faithfully follow the terrain, giving a harsher ride on bumpy roads that are effectively smoothed by larger ones. Bicycles with small wheels normally have their gearing adjusted to provide the same effective wheel radius as large ones, so pedalling cadence is not different. Small wheels usually weigh less than large wheels.
Small wheels, all else being equal, have slightly higher rolling resistance. On the other hand, they may have lower aerodynamic drag due to their smaller area which is proportional to their radius.