Terminology Of Bicycle Parts

GENERAL TERMINOLOGY

OF BICYCLE PARTS

Frame

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.