STI Shifters and Chain Drop

[Triskeliongirl]

It may depend which group you have, but what I mean is that you can push it gently or hard, and as you push ore it will move the chain over. Depending on how its been adjusted sometimes the gentle push will move it onto the next ring, and if you push more it will fall off, but sometimes you need to push more. Its really hard to explain online so I think its easier to have someone show you.

[Triskeliongirl]

FYI, trim means the ability by giving a gentle push to move the derailleur just a little bit without actually changing rings, for example to avoid the chain hitting the derailleur when the chain is crossed, or nearly crossed.