Derailleur hanger issues

Let’s talk about derailleur hangers. What are the good for?

On mountain bikes hangers are usually a piece of soft metal, that links the rear derailleur to the frame. I honestly don’t know if there is such a thing for road bikes. The derailleur or rear mech is >hung< from that mounting point – hence the name.

The idea behind them is, that there is a cheap exchangeable part that is supposed to break away and thereby protect the frame and possibly the derailleur, if it hits an obstacle on the trail. In essence that’s not a bad idea. But there are a few issues with that solution:

1. It’s not unreasonable to expect differences between hangers for quick release drop outs and through axles. As the position of the mounting point in relation to the axle should be the same for all bikes, one would think that two different versions would suffice.
   That is not the case. For some unfathomable reason no two mech hangers are the same. Their shape is usually keyed to a the frames of a brand and may even vary between frame models of a single brand.
   As can be expected this makes getting a replacement quite the hassle.
   There have been attempts to establish a sort of universal hanger by different brands … with the obvious result.

2. A universal hanger is difficult to establish, given the differences in frame design, material and “safety” requirements.
   The make of hangers range from stamped out seahorse shape from cheap alloy to artworks that were precision machined in all possible dimensions.
   I’ve seen a hanger bend and snap when a mechanic lifted the derailleur in order to remove the wheel and then there are hangers, that will survive the total destruction of frame and derailleur without a scratch. Some would have bolt the break away at the frame mount, rather than the hanger itself.
3. Some hangers will even interfere with installing or removing a wheel. There are manufacturer that suggest to first install the wheel and then tighten down the bolts that fix the hanger to the frame.
4. Rear mechs are not rigidly connected to the hanger. They can rotate rearwards and upwards to a certain degree and their position can be adjusted be the so called B-screw. Still at a specific overload the hanger breaks away. Now imagine the havoc that ensues, when the loose mech is scooped up be the spokes of the rotating rear wheel.
5. With the advent of 12speed cassettes the gaps between the sprockets got pretty tight. Chains are now slimmed down by decreasing the plate thickness of the links as the teeth of chainring and sprockets are already at a critical thickness.
   Due to the tighter gaps a small misalignment, e. g. from a bent hanger, have greater affect on the shifting quality.

So if a bent derailleur causes gear shift issues, you could alleviate that by installing a new hanger?
Well, maybe. See, even if a new derailleur hanger was true in it self and so were the derailleur, they would not necessarily be true to the cassette. There are still at least a handful of other possible sources that cause misalignment:
skewed seat- and chain stays, bend axles, dirt between faced parts, warped sprockets, play in suspension, …

So if you want to be a bike mechanic worth your salt, you better check the alignment of each newly installed hanger against the wheel before you start aligning or troubleshooting the gear shift.

A good source to buy a spare hanger, if you can’t get one for your bike at your LBS, is Schaltauge.de (external link) or schaltaugen.info (external link).

With all the short comings of the derailleur based system, it’s still the most efficient gear shift system on the market. Maybe we’ll see another increase in hub width or maybe someone comes up with a plan to better divide the real estate between dropouts. Maybe well see a return to 2by system with internal gear hubs or cranks. Personally I feel there is not much room to increase the cassette width and 1×12 covers all my needs on any of my bikes.