Viewed products

Top sellers

Brompton SA sprocket set 13T for any 3 spline Sturmey Archer



Sprocket set for 3 and 5 speed Sturmey Archer hubs with 3 spline / ISO fitting

Includes 13T sprocket, plastic chain guard, spacer and circlip

More details

We have 13 in stock


More info

Brompton / Sturmey Archer rear sprocket set 13T

Brompton / Sturmey Archer rear sprocket set - 13 teeth - for all 3 spline Sturmey Archer Brompton hub rear wheels

As used on standard 3 speed BSR (Brompton Standard Ratio) Sturmey Archer equipped hub gear Brompton folding bikes

This is the 3/32" sprocket - introduced in 2012 (compatible with all 3 spline Sturmey Archer hubs used on Bromptons) - the 1/8" sprocket has now been discontinued (in 2017)

If you currently have the wide 1/8 inch sprocket, you can change to this sprocket set - you will also need to change the chain (recommended anyway when changing sprockets)  - the front chainring can handle both 3/32 inch and 1/8 inch, so you will only need to change that if it is worn

How to remove the existing sprocket

How to install the new sprocket

How do I know if my hub needs a 3 spline sprocket?

The 3 spline / ISO (International Standards Organisation) hub is identified by the three groves onto which the sprocket(s) slide.

3 spline Sturmey Archer hubs include (but we are sure aren't limited to - so we would appreciate suggestions) Brompton/Sturmey Archer BSR (Brompton Standard ratio) hub, Sturmey Archer AW hub, Sturmey Archer SRF-3 hub, Sturmey Archer SRF-5 hub.

Below is a picture of showing the 3 grooves (or indentations running from outside to inside of the driver) for the splines on the sprocket used on a Brompton / Sturmey Archer BSR hub

Brompton Sturmey Archer BSR hub showing 3 spline grooves

From this straight on view it is easy to confuse the 3 spline grooves with the 4 grooves used for removing the hub internals cover

The below picture shows one of the ISO spline grooves on the hub driver 

Picture of ISO 3 spline hub groove on Brompton Sturmey Archer BSR wheel

If you have removed your existing sprocket, you see that there are 3 splines on the sprocket and 3 corresponding grooves on the hub driver.

Not sure if this is the right one? Our pictures show both the old, and the new version - both fit - they just require a different chain

The SA-13 sprocket kits consists of:

  • Plastic chain guard
  • Circlip - to hold the sprocket in place
  • Spacer
  • 13T sprocket with ISO fitting (3 splines) - silver in colour 3/32" (The sprocket width is the same as the older sprocket - at the bottom it is thicker)

Tools required: To remove the sprocket from the wheel you will need a flat head screwdiver (to prise the circlip apart), some brute force (to remove the existing sprocket) and some hand cleaner (as you are going to get dirty hands unless you wear gloves)

This video from Brompton shows how to remove / re-install the rear sprockets 

Chains for this sprocket set are dependent upon the number of teeth on the front chainring:
44T = 96 link chain - QCHAIN096DR
50T = 98 link chain - QCHAIN098DR
54T = 100 link chain - QCHAIN100DR 

Brompton Q part code: QRSPRSTACK-SA3-13
Brompton part number: 9024179 

Brompton 13T sprocket stack installation sequence

The older steel Sturmey Archer hubs use the supplier spacer, the newer alloy hubs do not

The installation sequence is the same for the 13T and 14T sprockets

1/ Install the plastic chain guard disk

Simply slide onto the hub and push snug to the spokes

Brompton BSR sprocket stack - chain guard only installed

2/ Install the 13T sprocket

This simply slides onto the hub driver - lining up the three notches on the sprocket with the three grooves on the hub

The sprocket has a wider part in the centre on one side - this should be facing towards the wheel, it ensures the correct spacing away from the chain guard

Brompton BSR hub with sprocket installed

3/ Install the circlip

Next up is the circlip - sometimes know as other names such as c-ring

The circlip fits into a groove on the driver, and holds the sprocket stack in place

It's fitted by prising the open part with a screwdriver then manoeuvring onto the driver - it can be the cause of some cursing

Brompton BSR hub showing circlip holding sprocket stack in place

When the circlip has been installed, it will have a small gap as shown in the above picture

The tension of the circlip and the fact it is seated in the groove will keep the sprocket set in place

A simple but effective solution

Now you can re-fit the wheel and go for a test ride :-)



Good product, great service

Bought as part of a drive train replacement for my 2007 Brompton, the bike is running great now, awesome service from Brilliant Bikes who did the fitting.


    springy circlip

    When fitting the stack start with the black disc , then then spacer / if you have the alloy hub not the steel one this part is not needed , then the cog with the stamped numbers facing out , and the raised edge facing the hub then the dreaded circlip. You can fit this with brute force and a small screw driver leveraging it into place . Took me 5 goes to get it on

    • 1 out of 1 people found this review useful.

    Write your review!

    Write a review

    Brompton SA sprocket set 13T for any 3 spline Sturmey Archer

    Brompton SA sprocket set 13T for any 3 spline Sturmey Archer

    Sprocket set for 3 and 5 speed Sturmey Archer hubs with 3 spline / ISO fitting

    Includes 13T sprocket, plastic chain guard, spacer and circlip

    Have a question?

    3 Question(s) answered - see below

    If your question has not yet been answered here, use the form below to ask something

    *(Required - so we can email an answer - we wont show it)
      Answered questions

    • Asked by Steve rich
      on 11/07/2019
      I have a recent Brompton with sturmy archer gears. I live in a hilly area and would like to somehow get a higher ratio to enable me to cope with the hills better. Is this possible? Answer:
      If you have a 3 speed or 6 speed - the most common - then you probably have a 50T chainring on the front. The easiest way to reduce the gearing is to change the front chainring from 50T to 44T (and take 2 links out of the chain / replace with a shorter chain)
    • Asked by chung pong
      on 06/02/2021
      I have a B75. Because I like to know if I want to change to 50T chainring, hence the chain (98) and the sprockets need to be changed. I am wondering whether this is the correct sprocket set I need. Many thanks. Answer:
      Yes this is the correct sprocket set to change.
    • Asked by Noob
      on 24/03/2021
      I currently have a 44T front chainring, and 14T rear sprocket. Would I notice much different going to a 13T rear sprocket? Answer:
      We agree and feel the difference will be small, you can calculate the gearing ratios using the following link: If you do decide to change it please let us know your thoughts.

    Related items / accessories

    Data sheet

    Comm Code87149990