The Flat-1 is the ultimate urban mini velo frameset. Designed for the streets of Japan, this frame was born out of the need for a compact bike on narrow streets and to store at home.
Available in one adult size, this single speed/fixed gear format frameset accepts 20 x 1 3/8 or 20 x 1.75 wheels (406 or 451 ETRTO) meaning the brake drop will alter depending on the wheel size used. Example – when using a 20 x 1 3/8 wheel size we recommended using our BRS 101 brakes which have a drop of 43-57mm.
We these framesets its important to think about gearing when selecting components for the build, due to the small wheel size a larger gearing should be considered to give a ‘normal’ gear ratio (i.e if running a 16t freewheel, then the chainring will probably want to be circa 50t+)
 
Geometry
Head Angle 73 deg
Top tube 529mm
Seat Tube 460mm
Chainstay 380mm
BB to fork 572mm
Rear dropout 120mmx10mm
Axle to brake 280mm
Specifications
Material Tig welded 4130 Cr-Mo
Headset Compatibility Threadless 1 1/8"
Seatpost 27.2mm
Seat Clamp 31.8mm
Max tyre clearance 451 = 40mm
Bottom bracket BSA Threaded 68mm