Mountain bike derailleur jockey wheels and cages

MTB derailleur jockey wheels and cages

These are the parts that save a derailleur after a crash or a muddy season, for a fraction of the price of a new model. Shimano and SRAM offer replacement pulleys and cages by model and number of speeds.

When should they be replaced?

• Pulley teeth become pointed or hooked: the chain no longer aligns properly.
• A lateral play appears in the pulley: shifting precision collapses.
• A continuous bearing noise while pedalling, disappearing when freewheeling.
• After an impact, a bent cage prevents correct adjustment, even if the derailleur is intact.

Which reference should you choose?

• Pulleys are specific to the derailleur model and the number of speeds: a 12-speed pulley is not an 11-speed pulley.
• Note the reference engraved on the derailleur (for example, RD-M8100).
• The upper pulley (guide) and lower pulley (tension) often differ: kits supply them as a pair.

Complete cage or pulleys only?

• Pulleys only : normal wear, with a straight cage in good condition.
• Complete cage : after an impact, or when the clutch spring has lost tension.
• On recent direct-mount drivetrains, the cage can often be replaced on its own, without removing the derailleur.

Bearings or bushings?

Original pulleys on entry-level ranges run on bushings: economical, but more susceptible to mud. Sealed-bearing pulleys spin more freely and last longer — a modest efficiency gain, but a real improvement in longevity.

To find out more: How to choose your mountain bike rear derailleur

See also: MTB rear derailleurs · MTB derailleur hangers · Drivetrain parts and accessories