Shifting problem

[KnottedYet]

I have trigger shifters - and someone has explained how to trim it - though it is only available to me if I have shifted up from the granny chain (per my LBS). I will try your experiment this afternoon. I tried to trim yesterday with the smidgen click on the shifter - but little seemed to help when I was in the middle chain. That does not mean that I was trimming it correctly...

Seriously, get off the bike and watch the derailleur move. It's really cool, and it's the best way to see how it works. Watch how the chain line changes as you go through the cassette. Watch how the chain gets closer and farther from the der plates.

Seeing how it all moves and works together will help you diagnose things when they're goofy. Anything you see helps the mechanic, too.

And if you figure out why the chain is rubbing on the der cage so hard that it's making noise and trying to shift all by itself, you might be able to fix it on your own! (which is always VERY cool!)