BWCC: Bike Parts Glossary
People who are new to the cycling world are often surprised by all the different bike parts that go into building one basic bike. With all the variety out there, working on a bike can quickly become a daunting task. To help eliminate some confusion, we've created this bike parts glossary. Here you'll find basic explanations for all the components you need to build a bike that is rideable.
The bike parts below are listed in alphabetical order.
Bottom bracket: A bottom bracket sits between the cranks and contains the bearing cartridges that allow the crankset to spin.
Brake cables/hoses: These connect the brake levers to the brakes themselves. Cables are used to control mechanical brakes. Hoses are used with hydraulic disc brakes.
Brake levers: These are the pieces you squeeze to engage the brakes. Mountain bike brake levers are clamped horizontally to the handlebar. Road levers are clamped vertically. Some brake levers (more commonly road brake levers) are integrated with the shifter.
Brakes: When you need to stop your bike, the brakes apply friction to the wheels, slowing you down. There are several types of brakes:
- Disc brakes consist of a metal disc that is attached to the wheel's hub. A caliper attached to the bike's frame or fork squeezes the disc between two brake pads to stop the wheel. Disc brakes can be controlled mechanically or hydraulically.
- V-brakes squeeze the rim to stop the wheel. They attach to the fork or frame in a vertical position and provide great leverage for easy stopping.
- Cantilever brakes put pressure on the rim as well. They connect to the bike in a more horizontal position.
- Road brakes are like V-brakes and cantilever brakes, but both brake pads are connected over the wheel, where the assembly attaches to the bike.
Cassette: Essentially, the cassette is a group of stacked cogs. It attaches to the rear wheel and grabs the chain so the wheel turns with the chain's movement.
Chain: The chain connects the crankset and chainring to the rear cassette, so when you pedal, the bike actually moves. When the chain is moved up a level or down a level on the cassette and chainring assembly (switching gears), you get more or less resistance in pedaling. In order to work properly, the chain should be compatible with the chainring, cassette and size of frame.
Chainrings: These are the larger rings connected to the crankset. They have teeth around the perimeter for grabbing the chain and holes (usually five) in the middle to connect to the spider. The diameter of the invisible circle these middle holes adhere to is called the "bolt circle diameter."
Crankset: Pedals are attached to crank arms, and a pair of crank arms makes up a crankset. Often, cranksets are sold with the spider and chainring. "Integrated cranksets" are those that have the spindle attached.
Derailleurs: These control the lateral movement of the chain. A front derailleur moves the chain on the front chainring, while the rear derailleur moves it on the rear cassette. Some derailleurs clamp on to the frame of the bike. Others are brazed on.
Fork: The fork assembly consists of the steerer tube, which is inserted through the head tube of the frame, and two posts, which hold the front wheel.
Frame: The bike frame is the tubing (usually metal or carbon) to which every other bike part is attached. They come in a variety of sizes and designs. Taller people require a larger frame than shorter people.
Grips: Usually rubber, grips are sleeves that slide over the ends of mountain bike and cruiser handlebars. They provide your hands with cushioning and greater control.
Handlebar: The tube you use to control the front wheel.
- Mountain bike handlebars stretch perpendicularly across the front wheel--basically one straight bar. The clamp diameters (where the stem clamps on to the handlebar) on mountain handlebars are either 25.4mm or 31.8mm (referred to as "oversized").
- The tube of a road handlebar curves out perpendicularly to the front and drops down and under to allow for a more aerodynamic and aggressive riding stance. The clamp diameters on road handlebars are usually 26.0mm or 31.8mm.
- Triathalon (or aero) handlebars stretch out in front of the bike over the wheel and allow the rider to rest on his/her forearms while riding.
Handlebar tape: This is wrapped around the ends of road bike handlebars to provide cushioning and grip. It is often leather or cork and comes in a variety of colors, textures and thicknesses.
Headset: Headsets help keep the fork secured to the frame, and they provide the ball bearings for smooth steering. When used with regular, non-quill stems, they can also cap off the steering tube.
Hubs: At the center of every bicycle wheel is a hub. It connects to the spokes and contains the bearings that make it possible for the wheel to turn. It is the hub that secures the wheel to the frame or fork. Rear hubs are equipped to hold the cassette. Front hubs are usually simpler and narrower. Some hubs are designed to facilitate disc brakes.
Pedals: These small platforms allow you to propel the bike with your feet. They are attached to the crank arms. Basic pedals are flat platforms. Pedals for more advanced riders have toe clips or cleats designed specifically for bike shoes.
Rims: The main piece of a wheel, the rim holds the tire and tube, and connects to the spokes. There are a few different kinds of rims:
- Clincher: These are the most common rims. The upper edge of a clincher rim has a lip that grabs on to the tire to create a seal when inflated.
- Sew-up or tubular: Some rims have the tire glued or sewed to the rim, so the tire and rim become basically one piece.
- Disc: Rims without a machined braking surface are called disc rims and are designed to use with disc brakes attached to the hub.
Saddle: In more common terms, this is the bike seat.
Seat clamp: This clamp keeps the seatpost from sliding around inside the seat tube. Most seat clamps today are quick-release, meaning you don't need a wrench or any kind of tool to loosen and tighten the clamp.
Seatpost: Saddles connect to seatposts, which are inserted inside the frame's seat tube. A seatpost allows you to adjust the height of the saddle.
Shifter cables: These metal cables connect the shifters on the handlebar to the derailleurs. When the shifter is moved, the cable moves with it and adjusts the derailleur, which moves the chain and changes gears.
Shifters: The levers you move to change gears. These are clamped on to the handlebars. Some are integrated with the brake levers.
Skewers: These are basically the axels of bike wheels. A skewer fits through the hub and clamps the wheel to the frame or fork. Today's skewers are usually quick-release, so no tools are necessary to loosen the clamp and remove the wheel.
Spider: The spider is the piece that connects the crank arm to the chainring.
Spindle: The spindle is the metal piece that slides through the bottom bracket to connect the crankset.
Spokes: These are the (usually) thin metal rods that connect the wheel's hub to the rim.
Stem: Connects the steering tube (on top of the fork) to the handlebar. A regular bike stem clamps onto the steering tube. A quill stem is inserted into the steerer tube. Both clamp around the middle of the handlebar.
Tires: There are several different types of bike tires:
- Road bike tires are thinner and have less tread than mountain bike tires. They are typically 700cm in diameter and are designed for riding on asphalt and cement.
- Mountain bike tires are wider and feature aggressive tread. They are usually 26 inches in diameter, and some are 29 inches. They are designed for riding on rugged mountain trails.
- Hybrid/commuter tires usually fit a 26-inch rim but don't feature the aggressive tread that a regular mountain bike tire would. They are designed to adapt your mountain bike for the road.
Tubes: Bicycle tubes come in different sizes to match different tires. One important part of a bike tube is its valve stem, where you connect a pump to inflate the tube. Some have a Presta valve, and some have a Schrader. Presta is smaller than Schrader, and your rim will have a hole designed for one or the other, so make sure your tube has a valve stem that matches the rim.