i've actually been meaning to write up a small instruction set about this very procedure. i corresponded with Sheldon a bit some time ago with some questions regarding the modifications he made to his own ASC shifter.. it was probably one of the last times we emailed...
you can modifiy either a 3 or 4 speed shifter, but it's easiest with a 4-speed. it's also possible to use a 4-speed shifter unmodified, but there will be one extra position to click through between middle and bottom gear.
to setup a 4-speed shifter for ASC use, you basically just have to take the shifter apart and grind off the position for 'low' gear. this would correspond to gear #2 if sturmey-archer had used a numbered system. they refer to the lowest gear as 'B' (bottom?)
i've uploaded a rough guideline and also a picture highlighting some differences between 3 and 4-speed shifters here:
andrei padlowski glen ridge, new jersy
On Feb 7, 2008 7:49 PM, John Clay <firstname.lastname@example.org> wrote:
> I need to convert a Sturmey 4-speed trigger for use
> with an ASC hub. I've heard that instructions exist
> but haven't been able to find any. Does anyone here
> know where I can find them, have a copy or know
> basically how it's done?
> John Clay
> Tallahassee, Florida