Bicycle Mechanics - Hanger alignment when there's no hanger
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06-27-10, 05:47 AM
Fairly regularly now I find myself working on low-end bikes having no derailleur hanger as part of the frame. The hanger ends up being part of the derailleur. And thus the Park Tools hanger alignment gauge is cannot be used.
How does one align such a built-in hanger?
06-27-10, 06:38 AM
use the calibrated eye and an old school park bt 3
06-27-10, 07:21 AM
Try by eye, replace the hanger or derailleur if that does not work.
06-27-10, 01:14 PM
The Mark 1 eyeball can be pretty good but it needs a reference to aid in lining up the cage and pulleys. But to do this well you want a flat plate like reference off the true axle axis to use as a reference that you can lay a ruler or other sight line spacer onto to judge the alignment of the derrailleur with more accurately. Something along the lines of an old hub with the cassette turned around backwards and use the face of the larger diameter cog as a visual reference plane. For this to work you may need to bust up the cassette and re-arrange some of the spacers and sprockets. But with a bit of effort you should then be able to lay a small straight edge along that sprocket face and extend the straight edge down to the derrailleur cage and sight things up from a number of angles. It's not perfect but I find that just sighting it using the wheel and derrailleur with no aids seems to be just too prone to picking the wrong sight line cues unless a trick of this sort is included.
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