by Corban Burns

Created on: March 19, 2010

A common problem with owning a mountain bike is dealing with the serious mechanical breakdowns that often occur, especially when your rear derailleur goes into the spokes of the rear wheel. Although this is usually not a sign of major problems, the results can be catastrophic for you, your bike and the wheel.

For all those that have had to deal with this unfortunate accident, you may well remember how it destroyed your hanger and critically damaged you wheel, the spokes, derailleur, and derailleur cable and its housing. This leads to the question: “How did this happen?” In most cases it is not because someone was tinkering with your adjustment screws on your derailleur. Rather, it is commonly due to the derailleur’s hanger being bent. This part, called the hanger, is actually built into the frame but can be removed and replaced. The only problem is, rarely does someone notice that it is bent. When it goes unnoticed and unchecked, the bent hanger will then misalign the entire derailleur system! This is shown by the bike’s poor shifting ability. At first this may not alarm you and chances are you won’t even take notice. Nevertheless, the damage is done when you shift downwards to your lower gears. If the derailleur hanger is bent in towards the wheel, disaster is imminent. The lower pulley of the rear derailleur will drive right into the spokes of your rear wheel. And if you happen to be pedaling there will be more extensive damage to your wheel. The damage may be so intense that you are forced to replace the entire back wheel.

When taking a closer look at the construction of these bikes, it was found that the derailleur’s hanger is made to bend. This prevents the actual derailleur or even the frame from being damaged at all. After all, the derailleur’s hanger is much cheaper and simpler to replace than a bike frame or the derailleur and its housing.

Now that you know what happens and how it happens, you may wonder what you can do in order to prevent this from reoccurring. Well, avoid laying your bike on the side where the drive train, gears, chain and etc are. Failing to do so can easily bend your derailleur and its hanger. Being sure to use your kickstand instead of lying it down on the ground will certainly help you prevent this from happening again. It would also be beneficial to give your bike a check every so often. In this way, you may be able to catch any defects and fix them before they cause any major damage.  

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