Brompton wheels & drivetrain specialist

4-Sprocket Kits for Sturmey Archer Gear Hubs - Updated Apr/2024

This kit is for: Brompton Wide Ratio (BWR) hub

(We also have 3-sprocket kits for Brompton BSR, and other Sturmey Archer hubs)

This conversion kit involves replacing the existing freehub body or the driver on the Sturmey Archer gear hub with our custom piece that can accommodate multiple sprockets, as well as modifying the Brompton post-2017 2 speed derailleur shifter from 2 to 4 speed. The new freehub is compatible with individual sprockets, down to 11T, and will make use of the cassette lockring instead of the cir-clip. The 4 speed indexed shifter has reduced stroke that is very easy to get used to. The shifter is also capable of shifting multiple gears in one stroke, similar to many mountain bike shifters. 

Updated Apr/2024:
There are now two choices for the left hand shifter conversion parts. Please refer to their respective pages for further details.
Post-2017 2 speed shifter,
P/T Line 4 speed shifter.

Pre-requisit / Required existing equipment
- Post 2017 integrated derailleur shifter, or the new P/T line 4 speed shifter
- Brompton chain pusher
- Brompton spring mechanism
- Derailleur type chain tensioner.

Any Brompton made between 2004/5 and 2016, (excluding the new P/L line), can be retrofitted with the above parts, if required. 

Kit Content:
- Freehub body kit (Freehub ASSY, cone nut, cone wrench, axle nuts, extension guide nut, tensioner nut) 
- Shifter conversion parts*
- Chain pusher modification parts
- Sprocket set (Including lockring. Some combintations include longer tensoiner pulley axles)**
- Chain tensioner longer axles and bolts
- 12 speed YBN chain 110L
- Installation instruction & tuning guide

* Choice of shifter parts for (1) Post-2017 LH 2S shifter, or (2) P/T Line 4S shifter
**Choice of sprocket combination: 11-13-15-19, or 12-14-16-19T.

Please note that the conversion will require re-dishing the rear wheel. Please ensure that you are comfortable with this task or your local bike shops offer this service. 

Please also note that for sprocket combination invovling 11T, the chain guide (protrusion) on the back side of the stock tensioner base plate may need to be removed. For more information please see here. Most aftermarket chain tensioners do not have such feature.

Due to the increased gear range, using a smaller chainring is highly advised.