The main purpose of the derailleur hanger is to break at the right moment and to save the more important elements of the bike: the expensive frame and the shifter. But seriously, a derailleur hanger really acts as a “fuse” in case of a sudden impact, no matter whether this is getting into the spokes, an accidental impact, a bad fall, chain blocking, etc. In such cases the whole force of the impact goes to the derailleur hanger, and the owner of the bike does not have to buy a new frame.
That’s why a machined derailleur hanger always has a special elaborate structure.
- On the one hand, it should be made of a strong alloy, allowing deformation to some extent — when these conditions are met, the derailleur hanger will not break at the slightest impact.
- On the other hand, it should have stress concentrators and weakening links (special holes, chamfers, material takeoffs, ledges, etc.). Thanks to them, in each particular case the derailleur hanger breaks to cause the minimum damage to the bike from an impact or a fall.
Have a pleasant and a safe ride!