Drivetrain Component study

Rear Derailleur

A sprung mechanism mounted near the rear wheel that guides the chain.

What does the Rear Derailleur do?

Moves the chain from one cassette sprocket to another to change gear and keeps the chain tight.

How does it work?

When the rider uses the shifter, a cable or electronic signal moves the derailleur sideways and the chain follows onto the next sprocket. A spring-loaded arm takes up the slack in the chain.

Materials & Construction

Materials commonly used to make the Rear Derailleur.

Aluminium

A light metal alloy and the most common material for frames and parts on entry-level and mid-range bicycles.

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Steel

A strong and durable iron-based alloy. It is used for frames as well as for parts that wear quickly, such as chains, cassette sprockets and brake rotors.