Originally Posted by
RoadTire
These Shimano STI M020 Rapid Fire 7 sp, ST200 group, came on the 1990 Giant mtb I picked up last fall. The question is - what is the shifting sequence? Seems a little erratic (assume I'll change the cables/housings. I did a semi - dissassembly and clean/lube of the cables, derailleurs and shifters last fall but I think I need to lube and clean better.)
On the rear cogs I can shift to larger cogs one at a time if I'm careful, other wise I can pull it up about 4 cogs in one stroke, then the next full stroke I can shift to the very largest cog.
On the front Biopace triple, I can
drop to the smallest gear in a single hard release of the trigger, or if careful, just release the trigger less aggressively and just drop from the largest to middle chainring.
For reference here is what they look like. Seems to be a hundred different styles of the same name.
Oh, that! That's how they're supposed to work. That's first-generation "Rapid-Fire". The idea was that you could downshift (go to a larger cog) one cog at a time if you were just slowing down a bit, or downshift several cogs at once if you found yourself confronted with a real steep climb. This was for mountain bikes, remember, and downshifts were always trickier than upshifts.
The small button activates the upshift on the rear (as you found). If the front is doing two shifts (all the way from big to small) then it's gummed up. The small button on the left side should only drop one chainring at a time. I bet it works better once it's cleaned out.
FWIW: Many people found the "push-push" design confusing, so the next generation introduced the "trigger" upshift lever aka "Rapid-Fire Plus". These went on to be the dominant design.
I think it'll work better once you've put new cables and housing on it. STI shifters don't like extra friction in the system.