How to trim down using Shimano Tiagra front derailleur shifters?

Question

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.

Answer 1

As per alex's answer and the manual you should be able to trim both up and down. Assuming you have that or a similar model Tiagra (there are multiple variants and I'm not sure all have a trimming option).

Answer 2

This may depend on whether you have ST-4400 or ST-4500 brifters (both are Tiagra). According to one ST-4500 manual (SI-0033A), you should be able to trim in both directions with a triple front derailleur.

However, according to the ST-4400 manual (SI-6CT0C) and the other ST-4500 manual (SI-6LP0A), trimming with the smaller lever is only available with double front derailleurs.

For indexing brifters in general, only being able to trim in one direction is common. With double chainrings, this usually isn't a problem, but with triple chainrings, trimming is more important. Unfortunately, there's not really anything you can do if your shifter wasn't designed to allow trimming in both directions.