Owners of Sturmey-Archer 3-spline coaster or hub-gear bikes who want to change gearing or replace a worn sprocket.
This is a genuine Sturmey-Archer 20T sprocket with the 3-spline fitting and a flat profile. It slides onto the splined driver of Sturmey-Archer hubs that use 3-spline sprockets, such as many of their coaster brake and internal gear hubs, and is held in place by a circlip.
Swapping sprockets is the simple way to change gearing on a hub-geared or single-speed coaster bike. A bigger sprocket makes pedalling easier for hills and stop-start riding, while a smaller one gives a taller gear for flat, faster roads. The chrome plating helps it resist rust on bikes that live outdoors.
3-spline fitting
Fits Sturmey-Archer hubs with a 3-spline driver.
20 teeth
A good all-round size for city and cruiser bikes.
Flat profile
Sits flat, with no dish.
Chrome plated
Resists rust on everyday bikes.
Sprocket
Great for
Maybe not for
3-spline, 35 mm inner diameter, flat type. Make sure your hub uses 3-spline sprockets and check whether it needs a flat or dished sprocket to keep the chainline straight. Chain width must suit the sprocket; bring the old one in if unsure.
Swapping the sprocket
Pop off the circlip with a small screwdriver, slide the old sprocket and any spacers off, then fit the new one the same way round and refit the circlip fully into its groove. You'll need to adjust the chain length or wheel position for the new tooth count.
Flip for chainline
Some hubs use spacers either side of the sprocket to set chainline. Keep the spacer order the same as it came off unless you're deliberately adjusting the chainline.
The original hub gear.
Sturmey-Archer began in Nottingham in 1902 making three-speed hub gears, and the name is still synonymous with internal gear and coaster brake hubs on city and classic bikes.
