The main parts of a bicycle are wheels, frame, seat, handlebars, and components.
The main parts of a bicycle are wheels, frame, seat, handlebars, and components. We also could consider the helmet as a key safety issue. Wheels give the fundamental purpose to the bicycle; that is why we call it a “bi” (meaning two) and a “cycle” (meaning turning). Tires and tubes are interchangeable. That's common customization we do is we change the tires. Now everything else on the bike is interchangeable meaning you could buy different parts, and swap them out.
The cassette on your bicycle can be found on the rear wheel and is a cluster of sprockets that are a part of the drivetrain. They slide onto the freehub, the ratchet system that controls the drive of your bicycle when you pedal and can have anything from 5 to 12 'speeds'.
Hub - The hub is in the centre of the bike wheel. It's made up of 3 parts: the hub shell, the bearings and the axle.
The frame - When you look at a bicycle, it's easy to see that the frame is the most important part of this vehicle. Not only is the frame the one that holds the entire bike up and together and allows you to sit on and steer it, but it also attests to the quality of the materials used.
The chain - is arguably your bike's weakest and its most important component, converting your body's raw power into a rear-wheel spin.
A thru-axle - is a wheel attachment system that secures a wheel on a hub between a pair of dropouts on a bicycle frame or fork. The thru-axle threads directly through the fork/frame holes and into the wheel hub, which makes the wheel secure from detaching.
Fork - the two-legged part of the frame that holds the front wheel in place. The steerer tube is a part of the fork that extends up into the frame through the head tube.
Bar ends - the angled extensions attached to the ends of some flat handlebars and riser handlebars that provide an alternate place to rest your hands.
Bottom bracket - the collection of ball bearings and spindle housed within the bottom bracket shell of the frame, which provides the "shaft" mechanism on which the crank arms turn.
Braze-ons - threaded sockets that may or may not be present on the bike frame that provides a place to attach accessories such as bottle cages, cargo racks, and fenders.
Cage - the preferred fancy name for a water bottle holder.
Cassette - the collection of gears that are attached to the rear wheel on most modern bicycles (see "Freewheel").
Chainrings - the gears that are attached to the right-hand crank arm nearer to the front of the bike. A bike with two chainrings is said to have a "double crank;" a bike with three chainrings is said to have a "triple crank."
Cog - a single gear on a cassette or freewheel gear cluster, or the single rear gear on a fixed-gear bike.
Crank arms - the pedals screw into these; these bolt onto the bottom bracket spindle.
Cyclocomputer - the preferred fancy word for an electronic speedometer/odometer.
Derailer - the device that is bolted to the frame that handles the job of moving the chain from one gear to another when you shift gears. The front derailer handles the shifting on your chainrings and is usually controlled by your left-hand shifter. The rear derailer handles the shifting on your cassette or freewheel and is usually controlled by your right-hand shifter.
Derailer hanger - a part of the frame where the rear derailleur is attached. It is usually an integrated part of the frame on steel and titanium bikes but is a separate, replaceable piece on aluminium and carbon fibre bikes.
Drop bar - the type of handlebar found on road racing bikes, with the half-circle-shaped curved ends that extend below the top, flatter part of the bar.
Dropouts - the U-shaped notches at the rear of the bike frame, and at the bottom ends of the front fork legs, where the wheels are held in place. So-called because if you loosen the bolts holding a wheel in place, the wheel "drops out."
Fixed gear - a type of bicycle that has a single gear and does not have a freewheel or cassette/freehub mechanism, so you are unable to coast. If the wheels are moving, you have to be pedalling. "Fixie" for short.
Flat bar - a handlebar with little or no upward or downward curve; some flat bars will have a slight backward curve, or "sweep."
Fork - the two-legged part of the frame that holds the front wheel in place. The steerer tube is a part of the fork that extends up into the frame through the head tube.
Frame - the main structural part of the bicycle, commonly made of steel, aluminium, titanium, or carbon fibre. Composed of a top tube, head tube, down tube, bottom bracket shell, seat tube, seat stays, and chainstays (see image). A-frame and fork sold as a combination are referred to as a frameset.
Bicycle Components
Freehub body - a part of the hub on most rear wheels, it provides that coasting mechanism that transfers power to your wheel when you are pedalling forward but allows the rear wheel to turn freely when you are pedalling backwards or not pedalling at all. The cassette is attached to the freehub body.
Freewheel - the collection of gears attached to the rear wheel found on most older bicycles and some lower-end modern bicycles. Both the gears and the coasting mechanism are part of the freewheel component, as opposed to cassette gears, where the gears are a solid, non-moving component, and the coasting mechanism is part of the wheel's hub.
Headset - the collection of bearings housed within the head tube of the bike frame; it provides smooth steering.
Hub - the central component of a wheel; inside the hub are the axle and ball bearings.
Nipple - A small flanged nut that holds a spoke in place on the rim of a wheel. Turning the nipples with a spoke wrench is what allows the tension in the spokes to be adjusted, in order to "true" the wheel, i.e. make sure the wheel is perfectly round.
Rim - the outer "hoop" part of a wheel. Usually made of aluminium, although can be made of steel on some older or low-end bikes, or made of carbon fibre on some high-end racing bikes.
Rim strip or Rim tape - a layer of material, usually cloth, plastic, or rubber, that is installed around the outside of a rim (between the rim and inner tube), to prevent the ends of the spokes from puncturing the inner tube.
Riser bar - a type of handlebar with a "U" shape in the middle. Some riser bars have a very shallow "U" shape, like on some mountain bikes and most hybrid bikes, but some have a very deep "U" shape, like on some retro-style cruiser bikes.
Saddle - the preferred fancy word for "seat."
Seatpost - the rod that connects the saddle to the frame.
Seatpost clamp - the collar located at the top of the seat tube on the frame, which holds the Seatpost at the desired height. Some Seatpost clamps have a quick-release lever that allows for easy, tool-free adjustment, while others require a tool to tighten or loosen the clamp.
Stem - the part that connects the handlebar to the frame. Do not call this the "gooseneck," unless you want to make it perfectly clear that you are a clueless newbie. Stems come in two varieties, threadless--which clamps to the outside of the fork's steerer tube, and threaded, which is held in place by an expanding wedge bolt inside the fork's steerer tube.
Wheel - the complete assembly of the hub, spokes, nipples, and rim.
