Brompton rear sproket on a SA AW 3 speed hub

[Gattopardo]

Can I use a normal sturmey archer sprocket like this https://www.tritoncycles.co.uk/components-c9/fixed-cogs-lockrings-c65/sturmey-archer-hsl-series-3-dog-sprocket-p17395 or does it have to brompton specific?

[Gattopardo]

Anyone?

I know i'll have to run a 1/8th chain even with a 3/16 chain ring upfront.

[LittleWheelsandBig]

If it is a normal (older) AW, then the normal SA sprocket is the correct choice. If it is a modern BWR hub, then you need a Shimano cassette spline cog. I'm not entirely certain about the modern AW on a current 3sp Brompton. You should be able to see the difference between the three half round keyways or the squared off Shimano spline, even with the cogs, circlip and all in place.

http://www.sturmey-archerheritage.com/index.php?page=history-detail&id=47
versus
http://www.jameshouston.com/sturmey-weather/

SA made both 1/8" and 3/32" cogs for their hubs but the Brompton 13t cogs were only 1/8".

[rogerzilla]

The S-RF3 takes normal SA 3-spline sprockets.  They will be flat and 1/8".  I don't think the smaller ones are ever dished anyway (large SA sprockets can be dished, which doubles chainline options).

Up to a 15T will fit, with appropriate chain length.