derailleur

Chain guide mechanism

A derailleur is the mechanism on a bicycle that moves the chain from one sprocket to another, allowing the rider to change gears.

Most bikes have two: a front derailleur near the pedals and a rear derailleur at the back wheel.

The word comes from French for "to derail"—the device deliberately derails the chain onto a different gear.

mechanism

chain

Linked segments forming length

cassetteMagnetic audio cartridge
sprocketToothed wheel for chains
tensionerMaintains strap or chain pressure

pulley · cable · indexing · pivot · cage · parallelogram · clutch · actuation · linkage · bracket

cycling

bicycle

Pedal-powered two-wheeler

chainringBicycle's front sprocket
cranksetPedal-to-chain transfer component
freewheelMove without propulsion

hub · cadence · shifter · downtube · drivetrain · Shimano · SRAM · peloton · velodrome

tuning

adjustment

Alteration to improve fit

alignmentCorrect relative positioning
calibrationAdjusting for measurement accuracy
fine-tuningSmall precise optimization adjustments

setup · maintenance · truing

shifting

upshift

Engage higher gear

downshiftChange to lower gear
trimmingCutting away excess
clickBrief sharp noise

ramp · wireless

Categories

cyclingbikes, bicycles, cycling, cyclist, cyclists
Bicycle Partschainring, cassette, crankset, sprocket, pedals
bike partsframe, top tube, saddle, pedal, chain
bicyclesmountain bike, road bike, BMX, tricycle, e-bike
Bikesbicycle, BMX, cruiser, mountain bike, road bike
bike touringbike tour, panniers, bikepacking, touring bikes, touring bike

Opposites

gear system type

derailleursingle-speed

One gear ratio only

fixed gear · fixie · coaster brake · direct drive · belt drive

bicycle component function

derailleurbrake

Device to slow motion

disc brake · rim brake · coaster brake

Family

Familiarity: Top 500,000
Profile: Used worldwide · Timeless · Concrete · Rated G