Originally Posted by
wesmamyke
Shifters will have one less click/detent than the number of gears, you have to count the starting position as 1. Generally Shimano shifters will index one gear past with varying degreees of success.
I think I've only ever setup one bike like that and had it shift perfect, was a 7spd XT thumb shifter running an 8spd cassette if I recall.
You're right about the XT- and perhaps Deore-level thumb shifters, even the 6s version had 7 solid detents.
But I don't think there are any other examples of "extra-click" SIS shifters, especially among road shifters.
My CX race bike has run 7s XT levers with an 8s cassette for over two decades, and I did slightly modify the spool groove diameter for better indexing with an 8s XTR cassette, and it's been race-day reliable over all of these years.