Brompton X4 Unibody Cog Set (11/13/17/21T) to modify 2 speed to 4 speed, or 6 speed to 12 speed

Stock 2/6 speed wheelset (or 3rd parties compatibleones) Compatible #X4UnibodyCogSet

Reuse your old wheelset (C Line) and expand to #WiderThanPTLine 4 speed gear range

Features :

1. CNC machined 4 cogs (11-13-17-21t) in One Unibody + 1.5mm & 1.8mm Circlip snap rings (MiniMODs)
2. SCM440H heat treated steel. ED-Electrophoresis deposition surface processed black
3. Most efficient drive output, crispy clear shifting reaction
   
4. 9 spline Shimano spec, compatible with 2/6 speed Brompton (now C Line and Eelectric B : BWR hub) wheelset. You will need 3rd party longer Tensioner arm and Derailleur Chain Pusher upgrade.
5. Compatible with most 3rd party 2 speed wheelset (MiniMODs, Hubsmith, H&H, Andoza, Joseph Kuosac, ORZ, RIDEA, Suncord ...) circlip snap ring or Lock nut type rear hub.
6. 11 Speed and up (narrower) Chain required. Leading teeth on-shift design for ultra smoothness.
7. Circlip type for maximum compatibility (1.5mm + 1.8mm custom snap rings included), also compatible with lock nut type rear hub.
8. 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 5x4 is possible

Note:

1. Older stock tensioner can only take upto 19t cog, so you will need a 3rd party (e.g. aluminum) tensioner, we have tested with MiniMODs, H&H, BooK, DCCH & Thx4ride (parallelogram derailleur), Suncord & RIDEA chain pusher type derailleur should work too.
2. You will also need following upgrade parts (Not Included) : 4 speed thumb shifter (ideal brompton stock), 11 speed or up Chain.
3. Disclaimer :
   • X4 Unibody Cog Set was based on our pupular X3 Unibody Cog Set (easy DIY 2s --> 3s with most compatible stock parts).
   • But for 4 speed mod, it will require other 3rd party upgrade parts (the derailleur tensioner system might be hard to adjust for some brands) and tighter precision requirement on Brompton rear frame (known to be not so precise since made manually).
   • We will recommand this to be done in our dealer shops, Only order here if no dealer near and you are very confident with your own technical skillset.