The heartache of a destroyed bicycle drivetrain
You are riding along a beautiful nature trail with an incline approaching. You shift up to your largest rear sprocket and before the climb, the bike comes to a halt and the heart breaking sound in heard. “crunch!” With tears in your eyes you gaze upon your derailleur. The lower pulleys of the derailleur has captured the rear spoke wheels and rapped itself upwards, twisting your chain.
This scenario is very common. Initially, the Bicycle Mechanic had installed the derailleur and properly set the limiter screws preventing the chain from dropping into the spokes. However, this accident is different than just a jammed chain. In this case the bottom pulley of the rear derailleur caught into a spoke and in beautiful synchronicity, was grossly pulled up.
This destroys the derailleur and bends the derailleur hanger (drop).
What causes a derailleur to be caught into the spokes?
Long answer, the bicycle owner improperly transporting the bicycle, or laying the bicycle down on the drive-side. This practice over time bends the derailleur hanger (drop) inward, which places the bottom pulley in the path of the wheel spokes.
Why would this cause the derailleur hanger to bend?
The hanger is a separate piece that forms part of the frame. In some cheaper bicycles the hanger is formed as part of the frame-set. Manufacturers discovered over time that when the hanger is formed as one piece with the frame, the scenario we describe here, destroys the entire frame. The solution was to make the hanger separate and in many cases the alloy used in making the hanger has a lower carbon value than the bicycle frame-set. The lower carbon value alloy will bend easier than the frame and therefore protect the frame from damage.
Three ways of preventing the derailleur hanger from bending.
- Install a kickstand – A kickstand prevents the bike from being set down on the drive-side. This optional accessory protects the bicycle from all sorts of damage.
- Care when transporting – whether you transport your bike in the back of the truck box or in the rear of an SUV, don’t lay the bike on the drive-side. (against the derailleur). If you are using a rear bicycle rack take care to ensure the rear derailleur does not get caught on the rack itself. Always shift the bicycle into the highest gear (smallest sprocket). This will raise the derailleur pulley up and backwards. This makes it harder to catch the derailleur on the rack.
- Inspect your bicycle – A quick look at the derailleur from the rear will show whether the is pulley are tilting towards the spoke. If the two pulleys are not at a 90 degree to the ground, don’t ride it. Take the bike to a mechanic to have the derailleur hanger corrected.
The derailleur hanger is an expensive little part. The derailleur hanger is also a complicated little piece. As varied as a puzzle piece, this part comes in various shapes, sizes and mounting styles. As a result, it can be expensive. A little care in the use and handling of your bicycle will prevent what can only be described as the most catastrophic self inflicted damage to your bicycle. Maybe just buy a kickstand after-all. They may look dorky, but who really cares.
Derailleur Hanger Dot Com – https://derailleurhanger.com