[1] An early proponent of small-wheeled adult bicycles was Paul de Vivie, better known by his pen name "Vélocio".
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" tires.
A large number of European manufacturers made U-frame small-wheeled and folding bicycles in the 1970s.
Smaller wheels more faithfully follow the terrain, giving a harsher ride on bumpy roads that are effectively smoothed by larger ones.
[3] It may be desirable for bicycles with smaller wheels to also be fitted with some form of suspension to improve riding characteristics.