What is wrong with my derailleur?

Likely the issue is either a bent derailleur hanger or the low limit screw needs to be adjusted. If you have not recently changed or adjusted your drivetrain and your chain is falling off into the spokes, your derailleur hanger is most likely bent inward. If you have a spare hanger, this is its time to shine.

What is Ghost shifting on a mountain bike?

Neil is right, most all “auto shifting” or “ghost shifting” is the result of cable-tension problems. If the cable is a bit loose, the derailleur will try to shift “up” to a smaller cog. If too tight, it will try to catch the next larger cog.

Can you ride a mountain bike without a derailleur?

Technically, a mountain bike can work without a derailleur. If your derailleur stops working, you can rig it to keep the bike working. However, you also have the option to ditch it completely and make it a single speed, if you wish.

Do derailleurs wear out?

Derailleurs will last almost indefinitely. The jockey wheels will wear out in time (tens of thousands of km) but the rest of the mechanism shouldn’t see significant wear.

Why does my mountain bike shifting gears on its own?

Most of the time, a skipping chain is caused by cable stretch. In the first half dozen rides on a new bike your shift cables stretch the most. They can also stretch over time as you ride. Shift down into the smallest ring in the rear cassette again, and press your shifter again to see if the bike shifts properly.

What is a rear derailleur?

The rear derailleur is the mechanism that shifts the chain at the rear sprockets. There are many different models but they all share the same basic design and functionality.

What kind of derailleur do I need for a mountain bike?

A derailleur for your mountain bike should match the specifications on the original derailleur. That is, while it doesn’t need to be the same model of derailleur, it does need to be the same brand, in almost every case. It also needs to match the number of gears, or have more intended. Meaning a 7 speed will fit for 5 and 6 speed bikes.

Why did my chain derailleur fail?

Here are the elements that have failed and other pieces of information: the chain has derailed past the largest sprocket the rear derailleur has rotated 180 degrees, and is caught in a spoke (between the frame of the derailleur and one of its sprockets)

Why is my rear derailleur bent to one side?

(in addition to Diado’s answer) I would suspect a bent derailleur hanger. Usually the derailleur cage should be perpendicular to the wheel’s axis. When the derailleur hanger is bent (it’s said that happens when the bike falls over or when squeezing it into parking positions) it will often be bent towards the wheel.