I have a Bike with HS 33 It is mounted on V/cantilever Posts .. (Koga WTR Not a Brompton)
That is a custom Mount* .. yes you need (?) the fork changed *( for Trials and Unicycle use)
There are Bodges from the BMX world putting V brake posts on a bolt on Plate .
The Urban have the Hose sticking straight up, from the caliper so Your Fold will be compromised
(& may not have the reach to the Rim on Brommys)
The lever on the HS22 is from the HS 33 of a few years back .
I put Kool Stop Dura 2 'salmon' inserts in the existing Brompton double pivots and they work Fine ..
Buy a Moulton and put the HS33 R Urban brakes on It, Instead of like Campag skeleton Side pulls, short reach.
Last edited by fietsbob; 03-15-16 at 01:05 PM.