I've got an older Vision SWB USS bike that I inherited from my brother in law.
It has a Shimano triple crank and Shimano thumb / forefinger indexed mountain bike shifters. I replaced the shifters after the ones it came with got damaged. It seems like the front shifter has too much throw for the front der. If I adjust the front der so the cage is centered on the middle ring, the der tries to throw the chain off the high side when I shift to the big ring. I have the upper stop screw adjusted to prevent this but I really have to push hard on the shifter to get the indexer to hold the der against the stop.
I have the cable attached to the der arm as far from the pivot as possible. I could move the cable to the other side of the clamp screw but this would move it closer to the pivot and should make the der move farther.
I know that some shifters have 5 indexed positions. This one has only 3. If it had 5 positions, I could half-step the der to trim it. What am I doing wrong?