It is 4 speed external cogs compatible (X4Ceramic). You will need to source your own spacers, cogs (shimano 9 splines). We will only include 2 sizes of snap rings (1.2, 1.5, 1.8 or 2mm. Pick 2 during checkout in "order comment". 1.2 and 1.8 will be default if not specified)
(b.) 1 Rear hub only (X4Ceramic).
You will need to source your own spacers, cogs (shimano 9 splines). We will only include 2 sizes of snap rings (1.2, 1.5, 1.8 or 2mm. Pick 2 during checkout in "order comment". 1.2 and 1.8 will be default if not specified)
(c.) 1 Front hub only (with ceramic ball bearings).
1. 4 speed upgrade will require more skill and patience than the 3 speed upgrade, which is most stock parts compatible.
2. For 4 speed upgrade, you will need improved tensioner and jocky wheel (for over 19t cog, some can take up to 27t). Longer travel chain pusher (DR spring set). We are in the process of sourcing and reviewing these 3rd party upgrade parts.
3. For now, you can just use the Combo kit as 3 speed upgrade as a start and reserve the possibility for future 4 speed upgrade project.
4. 11 speed chain is ideal for these thin profile cogs.
Parts introduction and tips on external cogs upgrade project
(a.) X3 Unibody Cog Set (MiniMODs)
3 sprockets (11-14-17T) in One Unit. Precision CNC machined
SCM440H heat treated steel. ED-Electrophoresis deposition surface processed black
Most efficient drive output, crispy clear shifting reaction
Plug and play, very easy to install and finetune. Stock components compatible
11 Speed and up (narrower) Chain required. Leading teeth on-shift design for ultra smoothness.
Circlip type for maximum compatibility (1.5mm custom snap ring included).
For 9 spline Shimano spec, compatible with Stock Brompton 2 speed hub (BWR 3x2 6 speed hub) and most third party external cog wheel mods (e.g. MiniMODs, Orz, Hubsmith, Joseph Kuosac, etc. )
Not compatible with Sturmey Archer SRF-5 (W) 5 speed hub or Brompton BSR 3 speed, but compatible with SRF-5(N) 10 (5x2) speed hub, so 5x3 is possible