Originally Posted by Duragrouch

What is gained in weight, is partly negated by the ability to use all-external gearing, being able to get by without an "overdrive" required for the smaller wheels. A lot of custom makers and Asian frame suppliers were making Brom clones on 406 wheels before Brompton jumped in. Additional benefits are ability for wider tires, and that and the larger diameter make off-pavement more possible, hence the Brompton designation of G-Line (Gravel).