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Sprocket set for 3 and 5 speed Sturmey Archer hubs with 3 spline / ISO fitting
Includes 13T sprocket, plastic chain guard, spacer and circlip
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Brompton / Sturmey Archer rear sprocket set - 13 teeth - for all 3 spline Sturmey Archer Brompton hub rear wheels
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 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
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
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:
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)
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
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
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
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
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 :-)