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TECHNIQUEAlign the derailleur hanger correctly

Stefan Frey

 · 14.04.2019

TECHNIQUE: Align the derailleur hanger correctlyPhoto: Robert Niedring
How to align the derailleur hanger correctly
The myth: You can simply straighten a bent derailleur hanger on your bike. Mechanic expert Florian Ohnesorg explains whether this is possible or not...

The problem

"The derailleur hanger acts as a predetermined breaking point between the frame and the derailleur. In the event of a fall or a knock against the rear derailleur, the derailleur hanger breaks first and the expensive rear derailleur remains intact. At least that's the theory.

In practice, however, the derailleur hanger often bends just by putting the bike down a little roughly. The chain rattles, skips gears when shifting or, in the worst case, even falls into the spokes in the lowest gear. Many derailleur hangers are already slightly bent when new. The high-quality XT then only runs like a cheap Shimano Altus. Only very few bike shops check this point during final assembly. In addition, modern derailleur hangers have become much more massive in recent years and are difficult to align precisely without risking breakage.

Just how important the angularity of the derailleur hanger really is can be seen in the new 12-speed shifting systems. If the derailleur hanger deviates from the plumb line by even a few tenths of a degree, the shifting behaviour deteriorates noticeably. For example, does the gear shifting work well in principle, but gets worse the further inwards you shift? Then in most cases the fault lies with the derailleur hanger. Minor deviations can usually be aligned, the right tool (e.g. Park Tool DAG-2.2, costs 72.99 euros at Wigglesport). If the derailleur hanger is badly bent, it often tears off directly during alignment. Unfortunately, I have to dispel the myth that you can simply straighten a derailleur hanger on the trail. In most cases, you only limit the damage. But precise shifting is no longer possible."

How do you measure correctly?

Use an alignment tool: Before starting the alignment, it is important that the rear wheel sits straight in the frame, has no lateral run-out and that all bolts are tight. Then use the alignment gauge to measure the top and bottom of the rim. If the derailleur hanger is straight, the distance of the gauge should be the same all round. If it is not, you can use the gauge to carefully straighten the eyelet.Photo: Robert NiedringUse an alignment tool: Before starting the alignment, it is important that the rear wheel sits straight in the frame, has no lateral run-out and that all bolts are tight. Then use the alignment gauge to measure the top and bottom of the rim. If the derailleur hanger is straight, the distance of the gauge should be the same all round. If it is not, you can use the gauge to carefully straighten the eyelet.
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Replace the derailleur hanger: If the derailleur hanger breaks or the deviation is too large, the only solution is to replace it. Unfortunately, there are countless different types of derailleur hanger. It is best to take the old one to the bike shop as a sample. This makes the search much easier. When fitting, observe the manufacturer's torque and, if necessary, apply some medium-strength Loctite to the bolt.Photo: Robert NiedringReplace the derailleur hanger: If the derailleur hanger breaks or the deviation is too large, the only solution is to replace it. Unfortunately, there are countless different types of derailleur hanger. It is best to take the old one to the bike shop as a sample. This makes the search much easier. When fitting, observe the manufacturer's torque and, if necessary, apply some medium-strength Loctite to the bolt.

For switching problems:

It is often not just the derailleur hanger that is to blame when gears jump or the chain rattles. Other factors can also have a huge impact on shifting behaviour. Here are the most common faults:

Worn chain: An old chain often shifts poorly. Especially with 1x11 or 1x12 drivetrains, the chains sometimes have enormous side play after a long period of use. Worn chainrings and cassettes also contribute to poor shifting.Photo: Robert NiedringWorn chain: An old chain often shifts poorly. Especially with 1x11 or 1x12 drivetrains, the chains sometimes have enormous side play after a long period of use. Worn chainrings and cassettes also contribute to poor shifting.Replace shift cables: Shift cables and outer casings also need to be replaced regularly. Relubrication usually does not help here, as the oil only binds dirt and draws it into the housing. Spliced outer covers are also a common fault.Photo: Robert NiedringReplace shift cables: Shift cables and outer casings also need to be replaced regularly. Relubrication usually does not help here, as the oil only binds dirt and draws it into the housing. Spliced outer covers are also a common fault.Screw loose? You should regularly check the tightening torque of the chainring and rear derailleur bolts as well as the derailleur hanger and cassette. The latter is often forgotten because you have to remove the rear wheel to check it.Photo: Robert NiedringScrew loose? You should regularly check the tightening torque of the chainring and rear derailleur bolts as well as the derailleur hanger and cassette. The latter is often forgotten because you have to remove the rear wheel to check it.Wrenching expert Florian Ohnesorg: The two-wheeler mechatronics technician has already been European Wrenching Champion and owns a bike shop in Ingenried near Schongau. There is hardly a bike problem that he cannot solve. Florian can tell how many kilometres the bike has covered just by smelling the fork oil.Photo: Robert NiedringWrenching expert Florian Ohnesorg: The two-wheeler mechatronics technician has already been European Wrenching Champion and owns a bike shop in Ingenried near Schongau. There is hardly a bike problem that he cannot solve. Florian can tell how many kilometres the bike has covered just by smelling the fork oil.


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Stefan Frey

Stefan Frey is from Lower Bavaria and loves the mossy, loamy trails of the Bavarian Forest as much as the rugged rock of the Dolomites. For technical descents, he is prepared to tackle almost any ascent - under his own steam. As an accessories specialist, he is the first port of call for questions about equipment and add-on parts, while as head of copywriting he sweeps the language crumbs from the pages of the BIKE print editions.

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