4 Speed
4 Speed Kit for Brompton 2 Speed Bike
Updated Apr/2024. Shifter conversion parts are now available for two shifters, (1) Post-2017 left hand 2S shifter, or (2) P/T Line 4S shifter. Please choose the preferred sprocket combination, and according to the shifter you intend to use. Sprocket combinations are abbreviated as follow. 11-13-15-19 -> 1-3-5-9, and 11-13-16-19 -> 1-3-6-9. Color choices, either black, or silver refer to the color of the hub end caps.
Introducing the 4 speed kit for Brompton standard 2 speed bike
With this kit, the gearing range increases from the standard 12T-16T (133%) to 11T-19T (173%). The kit basically bring the (older) 2 speed bikes to the same gearing range/ratio as the 4 speed P/T line, without costing an arm and a leg.
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.
Prerequisites:
- Brompton post 2017 LH 2 speed shifter, OR, the P/T line 4 speed shifter.
- Brompton Chain Pusher
- Brompton Spring Mechanism
- Brompton single/2-speed rear hub
The above are factory equipped on standard 2 speed bikes since 2017.
For 2013 to 2016 2 speed bikes, the newer integrated shifter is necessary and availble from Brompton. The spring mechansim is also best updated. The tensioner pulleys if worn should also be replaced. The same goes for 2004/5 - 2013 2 speed bikes, but the right hand brake lever would also need to be updated.
Other than the factory parts, this package is self contained. No other 3rd party parts are necessary.
Package Content:
- Lockring style 3/4S freehub body, with hub end caps.
- Shifter conversion parts,
- Chain pusher modification parts
- Sprocket set
- Longer tensioner pulley axles
- Axle extension nut
- 12 speed chain
- Installation instruction & tuning guide
Currently there are two sprocket combinations available, either 11-13-15-19 or 11-13-16-19. As well, the hub end caps are available in either black or silver. Please choose accordingly!
Notes:
- After installing the new freehub, the rear wheel will need to be re-dished. Wheel re-dishing is best done by professional with equipment/tools and expereinces. Wheel re-dishing in most cases, will not require changing the spokes.
- When using 11T as the smallest sprocket, the plastic protrusion on the back side of the chain tensioner will need to be removed, as it can interfere with the chain path.
