Brompton wheels & drivetrain specialist

Based on Brompton's patented chain pusher mechanism, this kit will bring your C line 2 speed bike to 5 speed with an expanded gear range of 191%~210%. 
 
The beauty of this kit is that it makes use of factory components as much as possible, for lower costs and increased reliability. 
 
This kit will make use of Brompton post-2017 integrated hub gear right hand shifter, or the Brompton P/T Line Advance Shifter. The factory shifters are not included in the kits, but are readily available through Brompton dealers. Other than the shifter, this kit includes all the items necessary for the conversion.
 
While this kit is designed for the post-2017 2 speed bikes, any Brompton manufactured after 2005 can make use of this kit, as long as the relevant factory parts (namely, the 2 speed rear wheel, shifter, chain pusher, cable anchorage set/spring set, and the 2/6-speed chain tensioner) are retrofitted.
 
Kit Content:
- 5 Speed freehub assembly for Brompton factory 2 speed rear hub
- Sprockets, spacers, and lockring
- Chain pusher modification parts & tensioner pulley axles
- Shifter conversion parts. Two choices of parts are avialble, for eitehr the RH 3S shifter or the LH 4S P/T Line shifter. 
- 12s Chain
- Installation & tuning guides, complemented with video instructions
 
Initially available with 11-13-15-18-21T sprocket combination. 1  0-12-14-17-21T will be available in September (tentative). For on other combinations, please contact us.

Please choose the color of the end caps, either black or silver. Please also leave us a note during check out on the choice of shifter parts (for either P/T LH shifter or RH 3S hub gear shifter)

Technical Information

• Please be aware that during the conversion process, the rear wheel will need to be re-dished due to change in the relative position of the hub with respect to the rim. Please be sure that you are comfortable re-dishing a bicycle wheel or your local bike shops offer such service.
• On the back side of the factory chain tensioner, there is a protruded chain guide designed for the 12T/13T sprocket. This protrusion will need to be removed. Most aftermarket chain tensioners do not have such chain guide.
• This kit is also compatible with most aftermarket chain tensioners that make use of factory pulleys, as long as the measurements are the same as factory tensioner.  
• This kit makes use of lockring style freehub body, which allows the use of individual sprockets. There are some aftermarket solutions that utilize factory style C-clip freehub together with 1-piece over-hang cassette. For ease of manufacturing, one piece cassettes are typically made of softer steel.  And when one cog is worn, the entire cassette will need to be replaced. One piece cassettes can be made very light and are generally used in the road bike racings where longevity is of no concern. On the other hand, lockring style freehubs offer greater choices of cog combinations, maintenance friendliness and cost saving in the long run.
• The converted 5 speed shifter has the ability of advancing 1 or 2 gears in one stroke. However, because the gear indexes are sufficient apart, it is not likely to advance 2 gears unintentionally.
• Please note that due to the additional sprockets, and the resulting in a more angled chainline, there are increased chances of chain drops during shifting or while on rough terrains. This is not a design flaw per se, but an inherent characteristic of multi-sprocket systems. This is also why Brompton P and T line bikes are factory fitted with chain catchers. If you experience frequent chain drop after the conversion, we recommend that you use a narrow-wide chainring to reduce the chance of chain drops. This is particularly important, when you are using aftermarket crankset that has an increased chainline.

 Should you have any techincal questions, please feel free to contact us.