As said,
771 – Top normal, i.e if you release all the tension in the cable the mech will sit over the smallest rear sprocket, i.e. the highest/top gear. If you want go uphill you have to press the shifter against the action of the spring to select lower gears. If you want to shift to a higher gear just press the release shifter and the spring action will shift up for you. This is the conventional set-up and works well with Rapidfire shifters
770 Low normal, i.e. if you release all the tension in the cable the mech will sit over the largest rear sprocket, i.e. the lowest gear. If you want to go faster you have to press the shifter against the action of the spring, but it has the advantage (depending on your point of view) that when shifting to lower gears when going up hill the spring action does the shifting so you get very quick down-shifts, i.e. rapid rise of the mech up the sprockets from the smallest to the largest. These work great with dual Control levers but work just as well with rapid fire. It just depends on whether you want quick upshifts (rapid rise 770) or quick downshifts (conventional 771).
Still confused??
Speaking to the Shimano bloke at Bike radar yesterday he said there is going to be no more rapid rise on future Shimano drivetrain and that there will be no dual control for the dynasis 10 speed stuff.
