Hi, Jack!
Uh, that's the SRAM Automatix and actually, it shifts itself based on rotational speed. The kick-back shift two-speed on today's market is the
Sturmey-Archer S2 series.
....right. It's been sitting over in the corner so long I forgot.
There are a couple of interesting online resources on how you can pull it apart and reset where you want it to shift, if the shift happens either at too high or too low a cadence for your personal tastes. I just need to get the wheel built, first.
