I have Shimano Tiagra 9 Speed shifters on my road bike. On my front deraileur, when I shift up (smaller chain ring to larger chain ring), I can control the amount my derailleur moves, therefore I can use this to trim the front derailleur going this direction to remove chain rub.
However, how do I trim going the opposite direction? On my shifter, when I shift down (larger ring to smaller ring), when I press the shifter, it instantly goes down to the next ring. There is no in-between and I can't control the amount it moves.
Are you supposed to be able to trim going that direction somehow? Sometimes, if I happen to find myself in my larger cassette gears but also my largest chain ring and I'm not able to adequately shift to a different chain ring (maybe going up a sudden steep hill or something), then I get chain rub. But the only way it seems to be to trim the front derailleur in this case is to shift to the lower chain ring, then shift back up to the larger chain ring but don't push the derailleur all the way into place.