Bicycle Derailleurs — Front, Rear, and How to Choose the Right One

The derailleur is the mechanism that moves your chain between gears. A well-set-up derailleur shifts crisply and quietly; a worn or incompatible one causes frustration on every ride. Here's what you need to know before buying.

Front vs Rear Derailleur

• Rear derailleur — moves the chain across the cassette sprockets. The most frequently adjusted component on the bike.
• Front derailleur — moves the chain between chainrings. Many modern drivetrains are 1x (single chainring), eliminating the front derailleur entirely.

Rear Derailleur — Key Specs

• Speed compatibility — must match your cassette and shifters (e.g. 11-speed Shimano rear derailleur with 11-speed cassette and shifters).
• Cage length — short cage for road and small cassettes; medium or long cage for wide-range cassettes (e.g. 11-42T). Long cage handles more chain slack.
• Maximum sprocket size — check the derailleur's maximum sprocket capacity matches your cassette's largest sprocket.

Front Derailleur — Key Specs

• Clamp diameter — must match your frame's seat tube diameter (31.8mm, 34.9mm, or braze-on mount).
• Chainring compatibility — match to your chainring size range and number of chainrings (double or triple).
• Pull direction — top pull, bottom pull, or dual pull, depending on your cable routing.

Electronic vs Mechanical

Mechanical derailleurs are cable-actuated, affordable, and easy to service. Electronic derailleurs (Shimano Di2, SRAM eTap/AXS, Campagnolo EPS) shift via motor with a button press — precise, consistent, and low maintenance once set up, but at a significant cost premium.

When to Replace

Replace a rear derailleur if the hanger is bent beyond straightening, the parallelogram is damaged, or the jockey wheels are excessively worn. Always replace the derailleur hanger (a sacrificial part) before the derailleur itself — hangers are designed to bend and break to protect the frame.

Browse our derailleur range to find the right match for your groupset.