Originally Posted by Duragrouch

Tires rare? If it's a rebadged Dahon 20" folder, the tires are 20"/406 x 1.5" or 1.75", many frames can also fit up to 1.95" section. Very commonly available, these tire sizes fit BMX bikes.

First generation Dahon bikes (I think never rebadged as Bickerton) 1980s and 1990s used 16"/305 wheels and tires. Those tires are not as common in bike shops but still available.

Smaller wheel Brompton bikes use 16"/349 wheels and tires, so quite common as there are many Bromptons in current use.