Originally Posted by
FBinNY
it's not you, it's crappy construction. You have a few ways to deal with it.
1-If the frame's surface there is truly flat, consider laying a sheet of emory cloth on a table and rubbing the hanger back and forth to sand it's mating surface flat.
2-If the frame's surface isn't flat, bed the hanger in body filler, and allow it to cure before installing the wheel.
3- leave it as is and tighten it as best you can.
No matter how you deal with it, you still should always check the hanger alignment with a wheel in and tightened. Actually, other than tightening it to riding standard, you don't have a choice because you need the wheel as the reference for the alignment gauge.
BTW- before doing this, try to figure how to get it so it's inner surface lines up with the inside of the dropout. You need to establish this position because the RD's travel range is designed around the assumption that it's mounted 6-8mm outside of the end of the right axle face (thickness of dropouts).
Your option #2 is probably the best.... I don't think I could sand / file the hanger flat by hand (too much material and too difficult to keep it flat while sanding), and leaving it alone is also not an option since the bike is currently not ridable.
I had a similar idea, but was thinking about using epoxy (and maybe fiberglass cloth) to mold a shim. It would probably be a little messy but would hopefully get the job done.
Good advice on the measurement of 6-8 mm outside of the right axle face.... I'll have to be careful about that.