Has opinion, will express
Join Date: Jun 2003
Mentioned: 16 Post(s)
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Always best to go the adjustment route first rather than force a solution by bending. A bent derailleur, especially if you aren't sure of what you are doing, could result in other unwanted things like poor changes. The bike's also under warranty and if the LBS identifies any "bending" when you do back to them, you've lost the warranty on that part. The cage is designed with certain features to make shifting of the chain better, and bending one section might change the dimensions of another section.
Barnett's manual has all the descriptions needed. BikerRyan is pretty well on track, but it's the clearance over the *big* chainring you need to make the adjustment for, and the clearance is between 1 and 3mm. You will have to move the derailleur out by hand, to check the clearance (because you've disconneted the shifter cable), and you may need to make several adjustments up and/or down with the seat tube clamp before you get it right.
The outer part of derailleur cage also needs to be parallel with the chainrings, and you will almost certainly need to check this as moving the seat tube clamp up and down may require a certain degree of rotation. Barnett's is a little detailed on this, but usually making sure the outside (right) side of the cage is parallel adjacent to the big chainring is sufficient.