austex9000

HALF STEP refers to a transmission design where a change between the front chain-rings result in half the ratio of a change between two of the rear cogs. Most times the two largest chain-rings will vary by 6 or less teeth.


Your pictures shows you've got a "granny" chain-ring too. NICE! So you've got HALF STEP PLUS GRANNY. The granny gives you a gear that is a very low one you'd use in a steep climb or when slowly maneuvering.


With HALF STEP you can make smaller changes when that is desirable.


Lets say your rear cogs are generally spaced at 15% between most cogs and you're speeding along in your highest gear when a black cat darts in front of you! You hit the brakes briefly and only slow a bit...the cat is now nowhere in sight. Change to the smallest of the two front chain-rings and you've geared down 7.5% instead of 15% ...just enough to regain your top speed in an instant by pedaling a few revs in the smaller chain-ring then shifting back into the largest chain-ring. You gotta keep that tandem moving, it's like a semi truck.


Now you encounter a steep grade. Use that GRANNY front chain-ring with the largest and second-largest rear cog to spin up that hill in a very low gear, preserving your knees for lifelong riding!