aka Tom Reingold
Join Date: Jan 2009
Location: West Village, New York City
Bikes: too many
Mentioned: 99 Post(s)
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Without a proper hanger alignment tool, it could be hard to do well, though I do it frequently. (Oops, that sounds like boasting.) Anyway, you have to align the hanger so the pulleys are in the same plane as the sprockets.
My procedure for alignment without the proper tool:
Leave the derailleur in the hanger. If you take it out, you will deform the threaded hole.
Eyeball the alignment.
Stick an allen key into the mounting bolt. Bend the hanger with the allen key.
Remember that there are two planes to adjust: the one with the axis visible from behind the bike and the one with the axis visible from above the bike. I think the one that's out of adjustment for you is the latter one. In other words, the front of the pulleys is to the left and the rear of the pulleys is to the right. Or vice versa.
Gee, I wish I could make a video.
is the proper tool. It's a bit too expensive for a home mechanic who won't have to use it more than once a year.