Hello! I have an old RSX (ST-A410). It pulls 13mm over two stages, I’m convinced it’s a triple but came from a stock 2x7 chaindrive. Thought I’d check with the pros!
But if it's a double, it will have 2 clicks downwards. A soft one for trimming when you want that slight movement to ride big/big and then a bigger clunk to drop to the small ring
These I believe used the same shifter for double or triple. They also used an mtb style top swing front mech and the associated pull ratio. The later evolution went to a normal style road front mech.
Thanks guys, appreciate the feedback. I’ve broken out the digital calipers, shifting up with the main lever (going from inner chainring outwards) it’s pulling 8mm of cable and then the next click is 5.6mm. (I do appreciate that I could just stop messing about and mount the thing! )