Originally Posted by DevilsGT2
A deraileur is simply a fancy spring that does what the shifter tells it to do. If it's not shifting smoothly, the shifter is as likely a cause as the deraileur itself.
right, but lots of things can go wrong with the derailleur, like poor adjustment of limit screws, poor cable tension, or various parts being bent. and with a perfectly good shifter up front telling it "hey man, go to the next gear!" the derailleur will just be all acting like he's drunk or high swaying back and forth like "gaba waka yabbahoo hoo!!!!" and then you get sloppy shifting. when everything is adjusted properly, the shifter can be like "hey man, go to the next cog!" and the derailleur will be like "HELL YEs, I WILL GO TO THE NEXT COG!! I WILL GO TO THE NEXT COG SO FAST AND SO SMOOTHLY YOU WILL THINK I DID NOT WORK BECAUSE IT WILL FEEL SO SEAMLESS, BUT I DID WORK AND NOW THE PEDALLING IS SO EASY FOR YOU YES!!!!!!!"
at least that's what happened on my bikes, when i work on them.
stuff can go wrong with the shifter too, but most of the time, it's the derailleur adjustment. in the shifter, the index points stay the same, and the shifter just doesn't come through as clear, and the shifter gets muffled, and the clicks aren't as defined. or the shifter just plain looses it's voice. in which case, a nice shot of triflow is in order.