What’s it all about then?


Simon Tolley our Director & Senior Mechanic shares a few thoughts and tips on the "good ole rear derailleur hanger".


So…  “Rear Derailleur Hangers”, “Gear Mech Hangers”, “Dropouts”, “Frame Savers”, call them what you will, are a lifesaver, usually made of an alloy, a relatively soft material, cast, stamped, cold forged or CNC Machined.

Attaching to your bike by bolts screws or both, from inside or outside the frame. The actual rear derailleur itself then bolts to this mech hanger. There are 100’s if not 1000’s of different types of rear hangers.

You will find that some hangers fit an enormous number of different manufacturer frames & multiple frame years like our CC007. Some models are however specific both to one manufacturers frame and even the specific year of manufacturer, meaning that a manufacturer could change the hanger for each year for essentially the same named frame, which hinders trying to source your replacement.

Mech hangers are of course a “sacrificial part” designed and fitted for the purpose of bending and / or breaking under stress, to reduce or eliminate damage to your frame & drivetrain parts.  As a result it is an impossible part to warranty.

A bent/broken rear mech hanger, is an extra expense and a pain, but very minor compared to the cost of repairing  / replacing your frame and / or damaged drive-train components. Hence the reason it exists and as is in the title, that’s what it’s all about!”

An everyday analogy to better explain a “Rear Derailleur Hangers” purpose, would be that the sacrificial hanger is akin to a fuse within a plug, inside electronics or electrical appliances. When overloaded the fuse is designed to blow, the fault be checked, diagnosed, remedied where applicable, then the fuse replaced & equipment set up and tested fully before use.

We all therefore need to avoid the chances of breakage as best we can, many risks can potentially be avoided, many can’t as they are everyday risks encountered while riding. Crashes perhaps, being the principle one.

So…..what should we reduce or avoid…. some go without saying, but we’re not always able to do it. Crashing, poor gear shifts, just being in the wrong gear particularly when climbing or on stationary starts are good examples of what to avoid and/or take care with.

Many reasons are potentially home grown from poor maintenance issues. Experience points the finger particularly at incorrectly fitted or worn chains, debris caught up in links, a chain that is too long or short for the crankset, rear mech and cassette combinations fitted. Not setting limit screws and having incorrectly indexed gears, lots of these can be removed as risks from good maintenance, left alone all can cause undue stress on your gear hanger.

Some of these examples are when drive-train parts are placed under some of the greatest load, creating massive stresses on the component parts i.e. chain, rear derailleur, crank set and so on

Simply keeping our component parts clean, free of debris, detritus and lubing them where necessary will go a long way to preventing catastrophe.

How many times have you caught grass, twigs, road gravel, tarmac in your chain and drivetrain parts, how long has it stayed there?. How many times have you removed parts, used a degreaser bath and thoroughly cleaned them, or had your LBS do it for you. Not at all? once? its comes as no surprise that whether your bike is a work hack, weekend warrior or carbon steed, it will suffer as a result.

Then you begin to realise why " Rear Mech Hangers" (a) Exist and (b) Sacrifice themselves when necessary.

Its a favourite pass-time to blame a part like a gear hanger for an incident, think twice, the gear hanger when it bends/or brakes underload is paying for our riding environment,  riding habits, lack of maintenance and mechanical sympathy's, and everyday abuse, so expect it to break at some time and carry a spare. Because with the best will in the world, what we plan to do as sympathetic bike owners with the up-keep of our bikes, tends to fall much short of our actions.

One more thing - Mechanics get it wrong too!, just because the local LBS replaced your recently departed gear hanger with a fresh sparkly new one,  it doesn't mean that under pressure they diagnosed a fault at all, that they diagnosed it correctly or that they ensured they had used a DAG tool on the new hanger just fitted before sending you home with your bike.

 Time spent differs hugely from one LBS to another. If an LBS needs to diagnose why a gear hanger failed, expect to pay for labour time to do it, its not just a gear hanger fitting charge. Given the nature of a gear hanger breaking, expect potential replacement parts form time to time too.

When we spend time checking an existing derailleur hanger or fitting a new derailleur hanger it is imperative that the derailleur is correctly aligned:



Of course without a "Derailleur Alignment Gauge - DAG for short", hangers can sometimes be aligned in only one plane and not another so full alignment should be checked  and amended with a “Derailleur Alignment Gauge”. If you haven’t got one, invest in one, learn to use it properly, if not then your LBS probably will have one.

When and only when its full aligned in both planes, the rear derailleur min/max stops should be reset, a new hanger will almost certainly sit in a slightly different position than an old one. Then follow with a full gear index / retune. Don't forget if any supplied screws are a tad on the longer side with your particular frame, file them down or take alternate action so they do not foul any other parts. An excellent guide for some these topics can be found here with Park Tool:

The alignment process applies whether you are replacing a damaged hanger as described above OR a replacing a hanger simplify for Aesthetic / Performance purposes.

It goes without saying that we would recommend a rear derailleur hanger is fitted by a suitably qualified or experienced individual, perhaps your LBS, local mechanic but with someone who in all cases is familiar with the aforementioned processes.