A limit screw for stopping the derailleur from shifting the chain out past the outermost cog.
Low limit screw
A limit screw for stopping the derailleur from shifting the chain in past the innermost cog.
Lower pulley wheel
The lower pulley wheel in the derailleur cage that pulls back on the lower section of chain to keep it under tension. Also known as tension pulley.
Upper pulley wheel
The upper pulley wheel in the derailleur cage that guides the chain from one cog to the next. Also known as guide pulley.
B-Adjustment
A screw used to adjust the spring tension on the mounting pivot, which affects the distance between the cogs and the guide pulley.
Cable fixing bolt
The mechanism that attaches the inner wire to the derailleur. The inner wire is usually routed through a groove in a plat on the derailleur, and a bolt or nut presses a washer or plate on top of the inner wire to trap and compress it in the groove. The groove in the plate is often hidden by the pressure washer/plate.
Frame mount
The bolt through the topmost part of the derailleur that attaches the derailleur to the derailleur hanger.
The structural piece, ususally a number of tubes joined together, to which all of the components are attached.
Fork
The structural piece that attaches the frame to the front wheel. The fork turns to allow the rider to control the bicycle.
Frame set
The frame and fork combination.
Head tube
The near-vertical tube that is the forward most part of the frame.
Top tube
The upper tube of the frame that extends back from the head tube to the seat tube.
Down tube
The lower tube of the frame that extends from the bottom of the head tube to the bottom of the frame (the bottom bracket shell)
Seat tube
The near-vertical tube that is at the middle of the frame, which the seat post slides into.
Bottom-bracket shell
The portion of the frame that contains the crankset bearing parts, which are called the bottom bracket.
Seat stay
The two tubes of the frame that start from below the seat and meet the chain stays at the center of the rear wheel.
Chain stay
The two tubes of the frame that go from the lower end of the seat tube and meet the seat stays at the center of the rear wheel.
Dropout
The fittings at the end of the fork, and at the juncture of the seat stays and the chain stays, to which the wheels are attached.
Derailleur
There are two such mechanisms, a front derailleur and a rear derailleur. The front derailleur moves the chain between the selection of gears on the crankset. The rear derailleur moves the chain between the selection of gears on the rear wheel.
Chain
The loop of links that connects the front gears to the rear gears.
Freewheel
The set of rear gears. In a general sense, the freewheel is the set of gears that the chains turns in order to apply drive forces to the rear wheel.
Crankset
The mechanism that is turn by the rider’s feet. It consist of two lever arms called crankarms, one to three gears called chainrings, and a bearing assembly that the crank arms rotate around called the bottom bracket.
Bottom bracket
The bearing assembly that allows the crankset to rotate in the bottom-bracket shell.
Wheel
The assembly consisting of the hub, spokes, rim, tire and tube.
Hub
The assembly at the center of the wheel that houses the axle bearings, and to which spokes attach.
Freehub
A hub and freewheel that have been combined into a single integrated assembly.
Spokes
The tensioned wires that join the hub and rim together.
Rim
The hoop at the outer edge of the wheel to which the tire is mounted.
Tire
The rubber hoop at the outer edge of the wheel assembly.
Headset
The bearing assembly that connects the fork to the frame and allows the fork to rotate inside the head tube.
Pedal
A mechanism that supports the rider’s foot. It contains a bearing assembly and is mounted to the crank arm.
Seat post
The pillar (usually a tube of metal) that attaches the seat to the frame.
Saddle
The soft structure that supports the rider’s posterior.
Stem
The piece that connects the handlebars to the fork
Handlebar
The piece that supports the rider’s hands and is turned to control the bike.
Brake lever
The levers that are operated by the rider’s hand to control the braking function.
Shift lever
The levers operated by the rider’s hands that control the derailleurs.
Brake caliper
The mechanism that squeeze against the rims to control the bike’s speed.
