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Other Bike Components

A bicycle is made of many small and large components.

These components benefit from regular maintenance. and hard working components like gear trains and tyres require replacement due to wear.

Understanding all the different component options ensures a correct bicycle fit, when choosing a new bike or upgrading an existing bike.

Derailleur pulley wheels

The rear derailleur arm contains two small pulley wheels that manage any excess chain length when in smaller diameter gear chain rings.

These pulley wheels are often referred to as "Jockey wheels".

A new derailleur typically uses black-coloured plastic (nylon/resin) pulley wheels with 11 teeth and typically weigh around 16 to 26 grams for a pair of wheels.

Shimano pulley wheels weight (estimates)

  • Dura-Ace RD-R9250 16g
  • Ultegra RD-R8150 22g
  • GRX RD-RX810 24g
  • 105 RD-5800 22g

For the majority of riders, the default pulley wheels are just fine and will last a long time (years, a decade or more).

Replacing with larger pulley wheels (usually the bottom wheel) with ceramic bearings can provide small performance improvements (several watts).

Why fit Custom pulley wheels

Many colours of wheel are available, making a visual enhancement to a bike (so long as you keep them clean).

The main benefit is smoother drivetrain performance when using wheels with larger number of teeth. The chain turns through a smaller angle which reduces friction as it traverse through the derailleur arm and on to the rear cassette. A larger pulley wheel should save a 1-3 watts of energy when peddling the bicycle.

Wheels with ceramic bearings should generate less friction, also saving a few watts of energy.

NOTE: low cost pulley wheels that have ceramic bearings may not be any better than steel bearings, but they shouldn't be any worse.

Aluminium wheels should be more durable than plastic wheels, especially in terms of being hit by stones or other hard surfaces.

These wheels do not have a heavy load placed upon them, so wear should not be an issue so long as the wheels are kept clean. Mud and grit could increase abrasive wear of the wheels (just like it does on the chain).

Aluminium is typically used to keep the main body of the wheel light. It is unlikely there will be any weight saving, but there should not be a weight penalty either.

NOTE: regularly cleaning the drivetrain (chain, pulley wheels, rear cassette, front rings) will provided greater performance

Which pulley wheels

Most existing derailleur cages will fit 11 and 13 teeth pulley wheels.

NOTE: check if pulley wheels are for up to 11-speed drivetrain, or for 12-speed drive train (usually have thinner pulley wheels)

For larger "oversized" pulley wheels, check if the derailleur cage has chain stoppers. These are parts of the cage which prevent the chain moving off the pulley wheel.

Off-set pulley wheels can be used where chain stopers of a cage prevent a larger center axle pulley from fitting.

Alternative pulley wheel cages are available that are designed for 15T or greater pulley wheels.

AliExpress has several low cost options for replacement pulley wheels

For larger "oversized" pulley wheels, a new cage should be obtained (these usually include the pulley wheels.