Brompton 1/3 Speed to 2/6 Speed External Derailleur Conversion Parts List

Note:

All parts in this listing will be stock Brompton parts, we will use link to listing of 3rd party equivilent upgrade parts if available.

The part order is from wheel back up to the thumb shifter. Some Brompton parts we do not stock but if enough interest, we might consider to stock.

A. Rear Wheel Free hub body (Shimano 9 splines)

For a rear wheel to take more than one cog, it needs to have free hub body with Shimano 9 splines spec. Stock 1 speed and 3 speed hub do not have this, but 2 speed hub or 6 speed (3x2) BWR hub do have this spec. You can tell from the picture below the looks are quite different.

Since most 3rd party wheelset do offer this type of free hub body (either with standard circlip / snap ring lock or lock ring type), so we won't provide brompton stock part here.

Here are some 3rd party wheel set available (contact us if only rear hub you need)

1. Seven Stars External 2/3 Speed Wheel Set Reinforced 28 holes Wide Rims (MiniMODs)

2. BUMBEE A349 2 speed WheelSet (Hubsmith)

3. Racing Wheelset A18C 25-349 2 speed WheelSet (Joseph Kuosac)

4. Racing Carbon Fiber Wheelset C38C 349 2 speed WheelSet (Joseph Kuosac)

5. Hawk B1 Plus Seamless Carbonized / Rim Tape Free / High Profile Wheel Set (Andoza)

B. Cogs / Sprockets / Freewheels (Shimano 9 splines)

Brompton 2/6 speed wheel uses Shimano 9 splines cog, there are different type of thickness and differnt Teeth count to choose from, please specify the cog size you want to order. This listing is only for one cog. You might also need spacer or washer to acommodate free hub body. We have misc components to fine tune the modification, please find more detail here.

For easier and more efficient drive, MiniMODs has design an X3 Unibody cog set which is compatible to most 2 speed free hub body (stock or 3rd party). This can turn the 2 speed wheelset instantly into 3 speed with ease. Highly recommanded.

C. Chain (10/11/12 speed)

Brompton uses 3/32" chain nowaday, so the chain should work with single or 2 cogs setup, however, if your modification project requires 3 cogs in the same free hub space (or even 7 sprockets project), it is recommended that you choose thinner chain to squeeze in. An 11 speed chain will mostly fit for the task. But you should double check the cog spacing to decide. We will not supply this here since there are too many options to choose from.

D. 2/6 Speed Derailleur Chain Tensioner w Jockey Wheels

1/3 speed brompton with only one external cog, require no movement in for gear change, hence the simple tensioner and jockey wheels with only one wall (dust cover). In order to change gears by moving the cog back and forth. The jockey weel will require two walls for the flaps on chain pusher to push against.

There are 3rd party tensioners (most with aluminum CNC machined), some are just improving appearance, but some do have functional upgrade such as the longer arm to take bigger cog (from 22t to 28t). Metal material is also stronger and more rigid hence less deformation after long time usage.

Here are some 3rd party 2/6 speed tensioner

1. Lightweight Xtensioner CNC Machined 25% Gear Range Expansion (H&H)

2. Extra Long arm linear chain push function up to 28T cog compatible (Suncord)

E. 2/6 Speed Jockey Wheels

Some of you might already have 3rd party tensioner, most of them will be stock jockey wheels compatible.

Here are some 3rd party 2/6 jockey wheels option

1. CNC 2/6 Speed Jockey tensioner wheels Ultra Smooth roll Pin bearings (MiniMODs) (MiniMODs)

F. Derailleur chain pusher & wing plate set assembly

This is the most crucial part that makes external cogs gears change possible. Install this on Bromtpon frame and adjust the limit screws on both side to match indexes on the thumb shifter. The later part of the following video expained how to adjust the chain pusher.

There are 3rd party part that use POM rods on both side to replace the meta flaps (will rub against aluminum jockey wheels) to protect jockey wheels surface, or with larger travel to push the cog furer in and beyon 2/3 cogs limitation. Please note, these upgrade parts are only the upper contact part, you still need the bottom base (and limit screws structure ) to get it works.

1.Improved Chain Pusher Longer Travel Mod for XTensioner Jockey Wheel (H&H)

G. DR Cable Anchorage & Spring Set

This srping set provide the required spring tension for thumb shifter to oeperate. It also allows the fixing point of the shifing cable.

H. Integrated Gear Shifter - DR 2 Speed

Left thumb shifter typically for the Brompton setup, new type integrated shifter replace the rabbit ear and sit on top of the brake lever. You can purchase this from local brompton store, such as sjscycle.

1. 2/6 speed left thumb shifter mod kit (Suntour x MiniMODs)

2. Indexed 3 speed thumb shifter handlebar LEFT w 1.45m cable (SunRace)

3. Retro Classic 3 speed thumb shifter handlebar (Sturmey Archer)

4. Indexed 3 speed thumb shifter handlebar RIGHT w 2m cable (Sturmey Archer)

5. XShifter Electronic Wireless Shifter for Road Bike MTB (Cell Cycling)