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Parts Glossary

  • Bottom Bracket
  • Brake Lever/Shifter
  • Brakes
  • Cassette
  • Chain
  • Crankset
  • Fork
  • Frame
  • Front Derailleur
  • Handlebars
  • Headset
  • Housing/Cables
  • Hub
  • Nipples
  • Pedals
  • Rear Derailleur
  • Rim
  • Saddle
  • Seatpost
  • Spokes
  • Stem
  • Tires
  • Wheel

Bottom Bracket

Being mostly encased in the bike frame, the bottom bracket is not often seen. It holds the bearings and a spindle that the crank arms are attached to. This allows the biker to pedal in a consistent circular pattern while tranfering their power to the rear wheel.

The main types of bottom brackets are square tapered, splined, and outboard bottom brackets. They come with loose ball bearings, sealed bearings, or in very high end bikes, ceramic bearings.

Bottom brackets, also known as BB's, usually have two specific measurements: how long the spindle is, and how big in diameter they are. The BB also needs to be the correct type to match the crank. Having a smooth BB is an important part of having an efficient bike.

Coming Soon

Brake Levers/Shifters

Many bikes come with the brakes seperate from the shifters, but most modern road bikes use combination levers, called STI levers. With these you can brake by pulling the lever, or shift by pushing the inner lever.

These newer type of brake levers/shifters allow the biker to keep their hands on the handlebars while shifting, which certainly increases the ease of shifting. They take a little time to get use to, but it is worth the effort.

Brake/shifters come in 8 speed to 10 speed for the right (probably 11 speed soon), which controls the rear derailleur. The one on the left comes as either a double, or a triple and controls the front derailleur.

Coming Soon


An extremely important part of biking is being able to stop. Thus, most bikes have brakes. Brake calipers, the actual braking mechanism, have come a long ways over the years.

Most road bikes come with dual-pivot brake calipers. They are fairly small, but provide strong braking, with a good feel. Other types are single-pivot, side pull, v-brakes, cantilever, or disc brakes, though the latter three are generally used for mountain bikes.

Through the use of cable tension, the brake caliper squeezes the rim, providing tons of friction and slowing you down. Specific brake pads can change the feel or power of a braking system. For max braking ability, hydraulic disc brakes are far superior.

Coming Soon


The cassette, or a freewheel on older bikes, is the collection of all the gears in the back of the bike. They range from 5 gears up to 10 or even 11 closely packed gears.

The cassette sits on a freehub that is part of the wheel. Functionally, they work together so that when you pedal down, the bike moves forward, but if you stop pedaling, the bike will keep moving because of the free-spinning part of the hub.

Cassettes come in various ranges of gear sizes. This allows the biker to pick a cassette that suits their riding habits. An 11-23 has higher gears, good for high speed racing, while a 13-30, might be more reasonable for touring or just cruising around.

Coming Soon


The chain is the device that gets the power from the crank where you are pedaling, back to the rear wheel. All of your power goes through that thin set of links. On fixed gear bikes, the chain is used to stop as well.

Chains are often designed for use with a specific number of gears. There are 8 speed chains, 9 speed, 10 speed, and single speed chains. Single speed chains are generally the strongest, but cannot fit between all the gears on the back on newer bikes.

The path of the chain on multi-speed bikes goes through the derailleur in the back, which takes up all the leftover slack. Chains do stretch with good use, and they also gunk up with grease and dirt. Keeping a good clean chain can go a long ways towards keeping the rest of your drivetrain in working condition.

Coming Soon


Acting as a giant lever, the crankset provides the starting point for generating the power to drive the bike. Generally a crankset includes the crank arms, chainrings (the front gears), and the bottom bracket.

To go along with the bottom brackets, there are square tapered, splined, and cranksets with outboard bottom brackets. They can come with 1, 2 or 3 chainrings, and can have various lengths, from 160mm to 180mm, though 170, 172.5 and 175 are most common.

Cranksets usually come as just that, sets. It is possible to pick out individual parts, but care must be taken to make sure everything matches, and that the Q factor is correct. The Q factor is a measurement to make sure the chain will be in the right place.

Coming Soon


The fork is the piece that connects the front wheel to the rest of the bike. Although a seemingly simple part, the fork can have a big effect on the ride of a bike.

The main parts of a fork are the blades, the crown and the steerer tube. The blades of the fork generally have a curve to them that adds an offset, or rake, measured in millimeters. Changing the offset a few mm can make noticeable handling differences, from sturdy and slow to turn, to fast turning, but twitchy.

Possible materials for forks can be steel, aluminum, carbon fiber or even titanium. Steel and carbon fiber are generally preferred as they can be quite stiff, while still retaining the ability to soak up micro bumps from the front wheel. Of course mountain bikes add shocks to their forks to take up much bigger bumps. Forks without shocks are called rigid forks.

Coming Soon


Often thought of as the heart of the bike, the frame is obviously a central piece in holding all the other pieces together. The frame is made up of several pieces of tubing all put together very precisely to create a sturdy bike.

Bike frames are usually made up of steel, aluminum, titanium, or carbon fiber, but can even be made of bamboo. Each material has unique characteristics and various levels of expense. Tubing can be made very high tech with special shapes and varying thicknesses, or they can be straight tubing welded together.

The parts of the frame are the head tube, top tube, down tube, seat tube, chain stays and seat stays. Each is combined with specific angles to create varying types of bikes. To many people, creating bike frames becomes a beautiful form of art.

Coming Soon

Front Derailleur

Although not used as much as the rear derailleur, the front has about the same responsibilities. Its there to change gears for the rider, while also keeping the chain from coming off the crankset.

Front derailleurs are simpler than rear derailleurs because they only have to manage 2 or 3 gears, and they don't have to take slack out of the chain. Essentially it just pushes the chain from one chainring to another through the use of cable tension.

Options include how it is connected to the bike, by clamping to the frame or connecting to a braze on already on the frame. As always there are varying models, with the highest being the lightest yet stiffest for the most precise shifing.

Coming Soon


By a connecection to the fork, the handlebars are used to turn the front wheel and steer the bike. Although it is possible to ride a bike with no hands, it is obviously not as stable as when both hands are on the handlebars.

Handlebars can come as simple flat bars, riser bars, bullhorn bars that point forward, cruiser type bars that come backwards towards the rider, or as dropbars, which are the common road bike type. Whatever the type, generally the wider they are, the more stable the bike can be.

Common roadbike sizes are 26.0mm and 31.8mm diameter tubing. For other bikes, 25.4mm is another common diameter, and various other sizes have been brought out by different companies. Matching the right size stem to the handlebars is an important part of having a safe front end to your bike.

Coming Soon


The headset is an often overlooked part. It holds the bearings that allow the fork and handlebars to turn smoothly. There are two sets of bearings, one on top of the frame, near the stem, and the other at the bottom of the frame, on the fork. A tuned headset will be tight so that the fork doesn't wiggle, but not so tight that the wheel won't turn.

Headsets come as either threaded, or threadless, with threadless being the newer type. Threaded headsets tighten by spinning a lockring down onto the end of the fork. Threadless headsets don't require the fork to be threaded because they tighten down by clamping into the inside of the fork steerer tube and then tightening with a bolt.

Headsets usually sit on the outside of the frame, but there are also integrated and internal headsets. All of the three locations of the headset have their pros and cons. Whatever headset you have, keeping it tightened correctly helps provide the best handling characteristics for your bike.

Coming Soon

Housing & Cables

Quite simply, the housing keeps the cables in line, which helps keep your bike tuned up. Old housing or stretched out cables are often the cause of a bike being out of tune.

Bikes have two types of cables and housing. The first are the brake cables, which provide tension to the brake calipers and brake the bike when pulled on. The second type are derailleur cables, which are a little thinner. By shifting, you change the tension of the cables, and the location of the derailleurs, which causes you to shift gears.

Most bikes come with a barrel adjuster at the ends of the housing near the rear derailleur. By spinning the barrel adjuster, you can add or subtract a small amount of tension. Often when a bike needs a tuneup, a simple 1/2 turn of the barrel adjuster will make it run much smoother, though a spin the wrong way can make things even worse.

Coming Soon


Every bike has two hubs, one for each wheel. The hub holds the bearings which allow the wheel to spin smoothly while also being stable and sturdy.

Hubs can have loose ball bearings, sealed bearings, or high end ceramic bearings. They come in various widths, usually 100mm for up front, and 120mm, 126mm, 130mm or 135mm for in the back. Newer road bikes use 130mm and mountain bikes use 135mm in general.

Keeping the hub well tuned is important because an overtight hub will add a lot of extra friction that will take away from your speed. Alternatively, loose hubs will make your wheel wobbly and can be unsafe, or at the very least, not as smooth.

Coming Soon


Did you know bikes had nipples? Often they have 72 of them! Nipples are the little tiny piece that connect the spokes to the rim. They essentially act as nuts that can be tightened or loosened to change the tension of the spokes, and thus the shape of the wheel.

Nipples are generally made of brass or an aluminum alloy. Brass is stronger, and harder to ruin while truing the wheel, but they are also about 3 times as heavy, which theoretically makes a slight difference because it is out on the rim where rotational mass plays a big role in acceleration.

Nipples also come in a few different lengths, and a couple widths, which must be matched up to the same width spoke that the nipple threads onto. Truing a wheel means adjusting individual spokes by twisting the nipple, so you need to have the right tool to turn the nipple without stripping it.

Coming Soon


In its most generic form, a pedal is just a flat platform that screws into the crank arms. Without pedals, a bike is worthless for transportation. Pedals come as platforms, toe cage pedals, or clipless pedals, which misleadingly named are pedals you can clip into.

Pedals have bearings in them that allow them to spin as your foot keeps them flat while the crank turns. Without good bearings, it is just one more piece that is adding friction to your bikes efficiency.

Most pedals use a 9/16 inch spindle, though some bikes have a smaller 1/2 inch spindle. The drive side pedal (the side of the bike with gears) screws in clockwise like normal bolts. However the non-drive side (the side of the bike without gears) screws in counterclockwise so that the pedal won't loosen while pedaling.

Coming Soon

Rear Derailleur

Changing gears is the primary job of the rear derailleur. By guiding the chain to a different gear, the rear derailleur helps a bike rider pick the right gear.

Rear derailleurs come in all sorts of varieties, from 5 gear derailleurs, to those with 10 or even 11 gear abilities. They can also have long cages, or short cages, depending on the type of bike.

Rear derailleurs are adjustable in two ways: the limit screws, which determine the max movement in either direction so that the chain doesn't come off; and secondly by the tension of the cable, which is generally the part that needs to be "tuned".

Coming Soon


The rim is the metal loop that is attached to the spokes and the tire.

Rims can be specific for different biking events. They vary between strong, light, and aerodynamic, though more expensive rims can achieve some level of all three. A rim is considered to be more aerodynamic by having a deeper profile. Standard rims are often about 20mm deep, while aero rims are 40-50mm and anything imbetween is a semi-aero rim.

The majority of rims have 32 holes for 32 spokes to help hold it together, but they can also come in 28h, 24h, 20h and 16h and some other company specific combinations. By itself, a rim is not very strong, and only becomes strong and stiff once it is trued as part of a full wheel.

Coming Soon


The saddle, the part you sit on, is an important comfort feature of a bike. Having the right saddle, also called a seat, can often determine if a bike is worth riding or not.

Contrary to belief, more padding doesn't necessarily mean a nicer saddle. Too much foam, gel or padding can cause your rear to go numb. Of course there are also many racing saddles that feel like pieces of wood, and probably have the same numbing effects for most people.

Everyone is shaped differently, and it usually takes some time to find a saddle that is the right fit.

Coming Soon


Basically, a seat post is just that, a post. Its job is to be able to be adjusted so that the bike rider can find the right height of the saddle. This is usually done by loosening the seat collar, moving the post, and retightening the seat collar.

The seat collar is a ring around the base of the post that clamps over part of the frame and keeps the seatpost in place. Sometimes this is done with a bolt, or with a quick release lever. If the seat collar is too loose, the seatpost will slowly lower in height while riding, or turn as your body moves.

Seatposts can come in steel, aluminum alloy, or carbon fiber. They can be bought with various lengths, and can have various offsets at the top, which means the saddle would sit further back than on a straight seatpost.

Coming Soon


The spokes of a bike wheel are an interesting part. Collectively, they hold the wheel straight and in shape so that it can roll smoothly, but this isn't done as you would first think.

Spokes work in tension. If you were to take a single spoke and lean your weight on it, it would crumble. However, if you took a single spoke and hung from it (with really grippy hands!) it would probably hold you. Wheels are built with this in mind. By tightening the nipples, the spokes are put in a constant state of tension, which holds the wheel in form, even when going over bumps.

Spokes are usually made of stainless steel these days, with galvanized steel being an older option. Titanium spokes can also be found, but come with their own set of problems. Spokes come in all sorts of sizes, usually in the range of 260mm to 295mm, depending on the size of wheel.

Coming Soon


The stem is a simple piece that attaches the handlebars to the fork. On older bikes, the stem was called a quill stem and works with a threaded headset to attach to the fork.

Stems have three basic measurements. First, their length, which just determines how far from the fork the handlebars are. Different lengths contribute to varying handling characteristics too. Second is the handlebar diameter, usually 25.4mm, 26.0mm or 31.8mm. Lastly, they must be able to clamp onto the fork, which is either 1" or 1 1/8" in diameter.

Stems can also raise or lower the handlebars by the angle they are made with. Changing the stem is often a good way to adjust the fit of a bike to be more custom to your preferences.

Coming Soon


The tires are where the rubber meets the road. Without tires, a bike would be terribly uncomfortable, if you could even ride one in the first place.

For most tires, they have a bead that sits in the rim, and the pressure of an inflated inner tube keeps the tire in place on the wheel. Tires come in widths from about 20mm all the way up to 3 inches wide for some mountain bikes. Tires can be smooth, for road racing, knobby for the mountain trails, or anywhere inbetween. Tires can also have varying thicknesses, to help prevent against flats, though this comes at a weight penalty.

There are such things as tubeless tires, which are glued onto the rim. Such tires have their advantages, but they are usually only used for racing or extreme enthusiasts because they require more time and/or money to deal with.

Coming Soon


A complete bicycle wheel includes the rim, nipples, spokes and the hub. Most wheels come complete from the manufacturer, though it is possible to build your own.

Building a wheel is a fun project for any bike enthusiast. Picking out the right parts, and learning how to put everything together can be an excellent learning process.

Upgrading a set of wheels often has the potential to be the greatest upgrade you can make to your bike. Loosing some extra rotational weight can make a large difference in how the bike accelerates and rides, though too light of wheels won't hold their form as well and might be unreliable.

Coming Soon


To see a description for a bike part, mouse over the part name on the left, or click on the photo to make a description appear.

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