The humble rear derailleur (or ‘mech’ to its friends) is a remarkable beast. When you think about what it’s trying to do it’s a wonder it works at all, let alone as well as it does. They don’t like going without periodical TLC, though, so if your shifting’s gone a bit awry here’s how to sort it.

rear-mech
mech 1

 

 

 

rear-mech
mech 2

 

 

 

rear-mech
mech 3
rear-mech
mech 4
rear-mech
mech 5
rear-mech
mech 5 proper
rear-mech
mech 6
rear-mech
mech 7

Usually that’s all there is to it. Sometimes, though, it just won’t work. Here’s the common problems and some possible answers:

Troubleshooting
Problem Solution
Mech won’t shift into smaller sprockets Turn barrel adjuster clockwise
Mech still won’t shift into smaller sprockets Clean and lube cables
Mech won’t shift into larger sprockets Turn barrel adjuster anticlockwise
Mech won’t shift into smallest sprocket Check high limit screw
Mech won’t shift into biggest sprocket Check low limit screw
Constant clicking in low gears Jockey wheel hitting cassette – adjust B-tension screw
Mech won’t work no matter what I do Jockey wheels possibly worn. Replace.

Mech itself possibly worn – can you wobble the cage from side to side lots?