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This question and its answers list the names of bike parts and cycling concepts.

Some Rules

  • Make sure you only put one term per answer!
  • Try to include an image if applicable
  • Include sources that contain detailed information
  • Add a link to the index in this question using edit.

Also, I made this a community wiki, so that anyone will be able to edit it, and to stop rep-hoarding


There's a handy reference at the Park Tool Co. website, a bike repair map; it's a diagram of a bike with all the parts labeled, and is very handy! At the moment, the diagram is up at parktool.com/blog/repair-help. (They've changed the URL in the past, so this link may break.)

A road bike has the following parts (source):

enter image description here

A mountain bike has the following parts (source): enter image description here


Edit: This page is meant to identify what things or concepts are (as per this thread in meta). If you want to recommend an accessory or a specific product you've found handy, please use the accessories page.


Contents:

Axle
Axle Nuts
BCD (Bolt Circle Diameter)
Bearing
Bonk/Bonking
Bottle Cage / Bottle Holder
Bottom Bracket
Brazed Frame
Brifter
BSO/Bike-Shaped-Object
Cable Pull
Cable Stretcher
Cadence
Chain Gauge
Chain Guard/Cover
Chain Tool
Chain Tug/Chain Tensioner
Chainstay Length
Chainsuck
Chamois
Clipless Pedals
Coaster Brake (foot brake / pedal brake)
Crank
Derailleur
Derailer Hanger/Derailleur Ranger
Disc Hub
Door Zone
Dropout
Dropper Post
Dunlop Valve
Fender/Mudguard/Mudflaps
Fixed-Gear
Flip-Flop Hub
Folding Bike
Frame
Gear Inches
Groupset
Handlebars
Headset
Hose Clamp aka Jubilee Clip
Hub
Hub Skewer
Internally-Geared Hub
Lawyer lips/lawyer tabs
LBS/Local Bike Shop
Luggage Carrier/Rack
Lugged Frame
Master Link
Mixte
Mountain Bike
Pannier
Play
Power Meter
Presta Valve/Presta Tube
Pump Peg
Q-Factor
Quick-Release
REI (Recreational Equipment Inc)
Rim
Rim Tape
Saddle
Saddlebag
Schrader Valve/ Schrader Tube
Single-speed
Skewer
Spider
Spoke
Stem
Suspension Fork/Rear Shock
Through/Thru Axle
Tire Clearance
Tire Lever/Tire Iron
Tire Saver
Track Pump/Floor Pump
Triathalon Bars/Triathlon Bars
Welded Frame

  • 6
    one term per answer would be beneficial – dotjoe Aug 26 '10 at 13:51
  • 2
    Should we add an "Anything not mentioned here" link? (With a link to sheldonbrown.com/glossary.html, of course.) – jensgram Aug 26 '10 at 15:22
  • 1
    Is there a way to link to a specific answer, so that in future questions you can use one of these terms and link to it for reference? – Kevin Aug 26 '10 at 16:13
  • 2
    Kevin: Under the bulk of the answer, there is a 'Link' hyperlink, which will link to the answer (its right above comment) – Dan McClain Aug 26 '10 at 17:12
  • 7
    @MarkIngram: useful things that aren't atually questions are what community wikis are for. – freiheit Sep 12 '10 at 17:47

77 Answers 77

10

Bottom Bracket

The bottom bracket is the bearing assembly that the cranks attach to.

The bottom bracket shell is the part of the frame holding the bottom bracket.

Generally, bottom brackets are made for a specific size of bottom bracket shell and a specific crank attachment.

Traditional bottom brackets are a piece that goes inside the shell and has the ends of a spindle/axle coming out on each end (which the crankset attaches to), or possibly the cranks somehow attach into it.

There are also external bottom brackets where the bearings are outside the bottom bracket shell, and the cranks have a spindle that runs through to the other side. Typically the bottom bracket in this case is a hollow cylinder with a bearing assembly permanently attached on one side and a way to attach the bearing assembly on the other (once inserted through the shell).

Most recently, there are various new-style ("press-fit", etc) bottom brackets, that are designed like an external bottom bracket, but rely on having a larger bottom bracket shell and fit inside the shell. They still have the axle/spindle as part of the cranks.

Also note that there are eccentric bottom brackets, which are really a bottom bracket that goes inside of an offset bottom bracket shell that fits inside the frame's bottom bracket shell. This allows the bottom bracket to be moved a bit, to tension the chain on a single-speed or fixed-gear bike.

  • Note: may be at the front or back of the bike rather than the bottom. And is not a bracket. – Мסž Apr 20 '11 at 4:38
  • I've recently been made aware of sealed, unsealed, and external BBs. Can here anyone expand on the difference between them? – Neil Fein Jul 31 '11 at 16:00
  • This actually describes the bottom bracket shell. The bottom bracket is the bearing assembly and is usually removable... – freiheit Oct 31 '12 at 17:25
  • @freiheit - fixed, feel free to edit further. – Neil Fein Nov 1 '12 at 19:52
  • Ok, I edited the heck out of it. I didn't mention sealed/unsealed, but I did explain external BBs and tried to explain the new external-style-but-actually-go-inside-a-larger-shell-BB style that I can't figure out the standard name for (it's called "press-fit" on one of my bikes, but the same thing also can screw in...) – freiheit Nov 2 '12 at 23:34
10

Cable Stretcher

A.K.A. "Fourth Hand" brake tool

a

The cable stretcher is used to stretch brake cables when installing brakes or new cable. It can also be used to tighten zip ties.

  • Can you explain what you would use it for? I'm betting most people don't install their own brake cables. – Joe Phillips Sep 6 '10 at 17:53
  • 1
    I have never had problems installing brake cables with a standard set of pliers. – Ian Sep 17 '10 at 9:22
  • @Ian - I've frayed cables by doing this. Perhaps I need practice! – Neil Fein Feb 9 '11 at 10:29
  • 3
    @neilfein, I tend to solder the ends of cables after I have cut them to stop any fraying. – Ian Feb 9 '11 at 11:37
  • 1
    @Ian superglue also works! – Will Vousden May 16 '16 at 8:01
9

Luggage Carrier

(a.k.a. Rack)

A luggage carrier, or rack, is a frame attached to a bicycle to provide space for a pannier or other back to be attached. They are frequently mounted over the rear wheel and are typically bolted to the bicycle and not easily removed.

Heavy-duty rear rack on a touring bike: enter image description here

Reference:

9

Frame

The frame is the skeleton of a bicycle. It's the part that all other parts are attached to. (Some parts, like the front wheel, are attached to other parts that are in turn attached to the frame.) The fork is sometimes considered a part of the frame, even though it's attached to the frame mechanically.

Frames are commonly made of steel, aluminum, carbon fiber, and sometimes more exotic materials such as titanium, wood, or bamboo.

Aluminum mountain bicycle frame:

100_7864

Parts of a bicycle frame:

enter image description here

(Image from wikipedia; credit and legalese)

9

Chainstay Length

The chainstay length is measured from the center of the front chainring (centered on the bottom bracket spindle) to the center of the rear cog (centered on the rear axle). Frames with vertical rear dropouts will have a fixed chainstay length, while frames with horizontal or adjustable dropouts will have an adjustable chainstay length, as the wheel hub centre can be moved to different positions.

The chainstay length is typically measured directly from point to point but might be measured horizontally (parallel to the ground) which will give a slightly shorter value. If possible, check the geometry chart to see how it is defined.

Touring bicycles typically have longer chainstays to allow for more heel clearance when riding with panniers, but this comes at the cost of increased flex due to longer tubes. Bicycles designed for sprinting and for the track typically have extremely short chainstays.

Chainstay Length

There are formulae for calculating chain length, based on chainstay length and cog sizes, which are used in online chain length calculator.

8

Saddlebag

(a.k.a. seat bag, wedge bag, etc.) Small bag designed to be attached to the underside of a bicycle saddle, usually large enough to hold tools to change a flat tire.

The name "saddlebag" is often mistakenly applied to panniers which resemble saddlebags used on motorcycles or horse saddles.

  • also known as a wedge-bag/pack – mgb Oct 22 '10 at 3:52
8

Hub

One of the central parts of a conventional bicycle wheel. A hub is essentially a flanged metal tube (somewhat similar in shape to a spool of thread). The hub links the rim, axle, and (in the case of rear hubs) drivetrain of a bicycle:

  1. Rim

    Holes are drilled in the flanges of the hub so that the spokes may be threaded through the hub, which holds the "heads" of the spokes. The spoke nipples in the rim hold the other ends of the spokes. This is how the hub is connected to the rim.

  2. Axle

    The hub also has a lateral hole through which the axle is inserted. When the wheel is moving, the axle does not rotate, but the hub, spokes, and rim do. The axle does not contact the hub directly; the two components have a set of cups/cones, bearings, and locknuts holding them together, similar to headsets and head tubes. This is how the hub (and thus the rest of the wheel) is connected to (but rotates freely around) the axle.

  3. Drivetrain

    In order to provide a means by which the chain can rotate the wheel, rear hubs can have at least one cog attached. (Front hubs do not have any drivetrain components.) There several different types of rear hubs which accept various drivetrain systems:

Furthermore, some hubs (front and rear) are designed to accept disc brake pads, while some other hubs (rear only) have drum or coaster brake systems built-in.

  • What is the actual name of the cylinder on which cassette goes? Wikipedia states "splined shaft", here you use term just "splines". – greenoldman Mar 26 at 18:31
8

Folding Bike

AKA Folder

A bike that's designed to fold down to a small package without disassembly. They usually have smaller wheels, and are designed to be taken on trains and buses. Many transit organizations that don't allow bikes during peak hours will allow folding bikes during these busy times. They also reduce storage space requirements, often useful in city apartments.

There are also bikes that do not fold, but are designed to be taken apart easily, with frame latches, quick-release latches, or hybrid folding/unlatching systems.

Folding bike, ready to ride

Folding bike, ready to ride

Folding bike, in folded position

Folding bike, in folded position

8

Internally-Geared Hub

A setup where, instead of the cogs and derailleur mechanisms are on the outside of the wheel, they're sealed in the rear wheel's hub. As the gears are sealed away from water and road salt, internally-Geared hubs require much less in the way of cleaning than traditional drive-trains. These hubs are popular with commuters or other utility cyclists that will be ride in the snow and rain. They are also popular on folding bikes, as they are suited for bikes taken on crowded trains. When coupled with a single front chainring, IGH drivetrains permit the installation of a full chain guard, which most external gear systems don't allow.

Internal hubs are slightly heavier than comparable external drive-trains.

Hub

Reference:

8

Lawyer Lips/ Lawyer Tabs

Bicycle forks with quick-release wheel mechanisms are often equipped with these. The intent is to make it less likely that the wheel will accidentally release if the quick-release lever is used improperly.

lawyer lips (thanks to sk606 for the image)

In practice, they make it difficult to use the quick-release without unscrewing the skewer, making the quick-release harder to use.

These are named what the are because of the rumor that these were added to bikes for liability reasons.

For bikes with disk brakes they are properly promoted to the role of retaining ridges. Under braking loads the wheel tries to twist out of the dropouts and the ridges serve to prevent that.

7

Crank

The part of the bicycle that the pedals screw into. The cranks themselves are, in turn, attached to the bottom bracket. The front chainring (or chainrings) attach to the crank.

Crank arms

7

Master link

Also known as:

  • Quick link
  • Breakable link
  • PowerLink™ (made by SRAM)
  • MissingLink (made by KMC)

A link inserted onto a chain so that the chain can be both assembled and "broken" (disassembled) without a chain tool. A set of pliers or a flathead screwdriver is usually sufficient to disassemble a chain with a master link.

Master link pliers are available to open a master link. Note that not all designs of master link are sold as suitable for re-use.

More information at Sheldon Brown's site.

enter image description here

Image from Wikipedia

6

Hose Clamp

A.K.A. Jubilee Clip

A ratcheting clamp often used to attach items to a bicycle fork or handlebars.

Flashlight attached to flat handlebars with a series of hose clamps.

Flashlight attached to handlebars with a series of hose clamps.

Jubilee Clip on Wikipedia

  • 1
    I see how the clamp goes around the torch, but how does it attach to the bars? Is there a second clamp, or does it twist around? – Hugo Jun 20 '11 at 8:59
  • 1
    There's a second clamp. – Neil Fein Jun 20 '11 at 14:14
  • 7
    Hose clamps can cut into paint an even metal if they're tight enough. You can stick a strip of old inner tube under the clamp to prevent this (and to provide better grip). – naught101 May 12 '12 at 3:03
6

Rim

The circular, U-shaped (in cross-section) part of a bicycle wheel that the tire and spokes are is attached to. Wheel-building is the process of attaching a hub to a rim with spokes; the name has connotations of smaller runs of wheels that are not machine-built, and are of presumably higher quality.

6

Mixte

A mixte is a step-through (low top tube or "ladies") frame with 3 sets of stays instead of the usual two. The middle set of stays usually runs all the way to the head tube replacing the top tube, but on some mixte frames, the top tube is still a normal single tube. The traditional mixte has those axle-to-head stays straight, but there are also designs where they're bent to give an even lower standover height. They still retain the usual chain stays and seat stays. This design keeps the frame strong and doesn't require a longer seat post.

I believe the word itself comes from French and means "mixed" as in "mix of women's and men's styles" or maybe even "unisex".

6

Spoke

The spokes connect the hub of a wheel to its rim. Spoke count is the number of spokes in a wheel, and a higher spoke count usually means a stronger wheel that can handle more weight and abuse.

Spoke tension (the force with which the spokes are tightened) can be adjusted individually. This is part of the process of truing a wheel, ensuring that tension is equally distributed in the wheel and that the rim is true, or straight. This is particularly important with bikes that have tight tolerances, but wheels that are trued are a benefit to any bike.

6

Tyre Saver

Small loop of wire attached so that it rubs continuously on the tyre as it rotates. This brushes off debris and reduces the number of punctures. These were popular mainly in the 1970's and 1980's, with the advent of lightweight puncture-resistant tyres they have almost disappeared.

tyre saver

  • Good work Mσᶎ. I think we also called them stone pickers or tire pickers, but my recent research only found stone picking machines to remove stones from farmland. – andy256 Jun 10 '14 at 3:41
6

Bonk

Expression used by cyclists to describe exercise induced low blood sugar levels; being a feeling of light-headedness and weakness in all limbs.

Similar to The Wall in running. Has fallen out of usage in recent years due to alternative meanings.

The cure is to stop riding and eat something sweet. Water and electrolyte won't help. You also need to rest for a while.

Also known as Crashing, Blowing Up, or Running out of Steam/Gas/Fuel, or Empty Tank.

Its not a pleasant feeling, and should be avoided by eating regularly on long rides.

6

Chamois

The padding in a pair of bike shorts. Sometimes chamois cream is applied to the chamois to prevent chafing while riding.

  • 5
    And chamois cream is better known as "butt butter". – Daniel R Hicks Jul 31 '11 at 18:24
6

Brazed Frame

see also lugged frame and welded frame

A method of joining steel frame parts together by melting brass into the joins between frame tubes. Frames can be fillet brazed or use lugs, which are extra, normally cast steel, parts that the frame tubes slot into before brazing. Lugs make building a strong frame easier, provided you have exactly the right lug for the situation. Fillet brazing offers more freedom, but also more skill is required to produce a strong joint.

Shown is part of a fillet brazed frame, with the grey steel contrasting with the copper-coloured bronze

fillet brazed frame

This contrasts with welding, where the parent metal is melted and the same or a very similar metal is added as filler.

5

Cage/Bottle Cage/Bottle Holder

This is a mechanism to hold water bottles on a bike frame. They can be made of steel, aluminum or carbon. Most attach to the frame via preinstalled threaded holes, although on older frames an attachment that wraps around the entire tube was needed as an adapter. A couple examples of cages are shown:

Carbon Fibre Aluminum

For time trials and triathlons, there are also cage adapters that attach to the seat and provide mounting points for extra water bottle cages and spare tubes/inflators, and a few new mounts place a water bottle between the extension of an aerobar set.

Behind the seat Between the extensions

5

Mountain Bike

Often abbreviated as MTB.

A bike with sturdier wheels (usually 26" or 29") and wider tires - around 2" wide - meant for riding off-road.

Mountain bikes commonly come with only front suspension (hard tail), front and rear suspension (full suspension) or no suspension (rigid; also may be referred to as a hard tail). A rare configuration is the soft tail where only rear suspension is present.

Thicker frame tubing and flat handlebars are common features of mountain bikes.

5

Spider

The part that connects the cranks to the chain rings. Typically spiders have 5 legs, but 3, 4, and six legs are also common.

Image from trekstorecolumbus.com

5

Welded Frame

A frame made by melting the tubes it is built from at the joins, typically with a similar metal added as filler. Mass produced aluminium and steel frames are almost all built this way as with modern machines it is very fast and cheap.

welded frame joints

5

Thru Axles / Through Axles

These axles are more like bolts for your wheels. Historically bicycles have used dropouts for both wheels, but the advent of MTB and disc brakes has shown a requirement for a system that cannot drop the wheel under braking, and adds stiffness.

A Through Axle looks more like a hollow pipe, compared with a conventional QR as per: from http://cdn.mos.bikeradar.imdserve.com/images/news/2014/02/14/1392416431992-ecxclyd8c6n5-700-80.jpg

A Through Axle has no dropouts - as this image shows there is a solid line of white metal from the fork all the way around From http://fcdn.mtbr.com/attachments/beginners-corner/789715d1365723144-need-help-new-bike-assembly-thru-axle-axle-pic.jpg

Contrast with Quick Release

The purported advantages are:

  • Increased stiffness when turning
  • Shock Load is shared between both fork legs more evenly
  • Less rotational torsion on the fork leg with the brake caliper attached.
  • Thicker axles are harder to break - a 15mm axle has more strength than a 9mm QR.
5

Dropout

In the context of bicycles dropouts are a kind of fork end, where the wheels are attached. Dropouts are employed on most bikes; on some mountain bikes the axles pass through holes at the end of the forks.

We often use dropout for any slot to hold the axle at the end of forks, but strictly speaking, a dropout is a fork end where the wheel can be removed from the frame without taking the chain off first. It's called a dropout because after loosening the quick release or nuts the wheel will drop out when the bike is lifted off the ground. It is much quicker and easier to remove wheels with the bike the right way up than when the bike is upside down.

The image below shows a Colnago horizontal dropout in a Surly frame; a typical example. It has adjustment screws and an integral derailleur hanger. Colnago horizontal dropout in a Surly frame

Front dropouts are vertical, and some rear dropouts are also vertical.

This image (CC BY-SA) from Wikipedia shows a fork end that is not a dropout. The wheel cannot be removed without removing the chain.

fork end

5

Lugged Frame

also lugs

A method of frame-building where at least the major joints consist of frame tubes inserted into castings (the lugs). For steel frames, lugs are hand-made by bending and filing rather than casting. Lugged frames are normally brazed, but can also be soldered (with lead or silver rather than brass) and occasionally glued (the Windcheetah trike used glued aluminium, for example). Historically this was very common, and many classic steel frames were built this way. Today with better welding technology it's rare, especially in mass produced bikes. Another alternative construction method for steel frames is fillet brazing.

classic Italian lugged frame

A small minority of carbon frames are lugged, for example the Colnago C-64 (link from Cyclingweekly). The main alternative to lugs in carbon frames is monocoque frames, where the entire frame is molded in one piece.

enter image description here

5

Power Meter

A power meter measures your power output. This is useful for training purposes. This discussion on StackExchange outlines what power meters are and why cyclists, mostly those interested in serious competition, might want one. Power meters are ubiquitous in professional road racing at the time of writing.

Power meters can be mounted in various places on the bike. Note that the companies listed below are examples and are not product recommendations, nor are the lists exhaustive.

  1. The chainring spider. SRM, a German company, may have been the first company to make power meters, and they made spider-based power meters. Power2Max and Quarq (owned by SRAM) are other companies in this category. Power2Max focuses on cranksets which have removable chainring spiders. Quarq makes their own cranks instead.
  2. The rear hub. Not long after SRM, Powertap introduced hubs that measured power. To the writer's knowledge in 2019, they're the only such company in this category.
  3. One or both crankarms. In this type, a strain gauge is bonded to the crankarm(s). To the author's recollection, these came later than the first two categories, and Stages was a pioneer in this regard. Pioneer and 4iiii are two other companies. Infocrank designed a full crankset from the ground up, with strain gauges mounted internally.
  4. Pedals. Yet other companies have placed strain gauges in the pedal spindle, e.g. Garmin (they bought a company called Metrigear), Favero Assioma, Powertap. Brim Brothers, which is now defunct, were testing a version that measured at the pedal-cleat interface.
  5. The crank spindle, is a more rare location at the time of writing. Easton/Race Face and some models of Rotor cranks have these.
  6. The above 5 categories can be called direct force power meters (DFPMs), because they directly measure power (actually torque and cadence). One other type of power meter estimates power from air resistance, but this requires some assumptions (e.g. rolling resistance from your tires, drivetrain resistance). These units may be able to work independently to estimate power, or else they could work in conjunction with a a direct force power meter to estimate your aerodynamic coefficient drag. The Velocomp PowerPod can be a standalone power unit. The Notio Konnect appears to only work in combination with a DFPM.

Power meters in categories 3, 4, and 5 can either: a) directly measure each leg's power, or b) measure only one leg's power, usually the left, and estimate total power by doubling that. b) is obviously cheaper, but it can be less accurate. Riders with a known leg imbalance (e.g. after an injury) may want to take note of this issue.

Power meters in category 1 and 2 directly measure your total power from both legs. They may be able to estimate each leg's contribution through algorithms. Some have criticized this estimation as potentially inaccurate.

Last, power meters actually measure both torque and cadence separately, and calculate power from those two parameters. They measure torque through strain gauges. They measure cadence through magnets and reed switches (more rare) or accelerometers. Both processes have some level of inaccuracy. For example, InfoCrank issued a white paper (dated 2017) arguing that cadence measured through magnets is more accurate than via accelerometer (but they have updated their power cranks to measure cadence via accelerometer or magnets).

Image of power meter

Reference: Wikipedia

  • @DanK I was thinking that SRM was a German company, and some wires got crossed in my head, and I made the rather amusing typo about Metrigear being a country that you caught. Thanks! – Weiwen Ng Sep 27 at 14:04
4

Chain guard/Chain cover

It's a frame, usually made of plastic or metal, that covers the entire length of the chain or only the upper part, mainly for protecting the rider from the dirt and lubricant on the chain, but can also protect the chain itself.

http://commons.wikimedia.org/wiki/File:Bike_chain_guard_full.JPG

http://upload.wikimedia.org/wikipedia/commons/thumb/6/69/Bike_chain_guard_part.JPG/320px-Bike_chain_guard_part.JPG

4

Pump Peg

A pump peg is a small protrusion on a bike frame which is intended to facilitate the mounting of a "frame pump". Depending on the style of the frame, the peg may be positioned to allow the pump to fit on the underside of the top tube (of a standard diamond frame) or on the trailing side of the down tube. The peg is designed to mate with a corresponding hole in the end of the pump.

Some schemes have a peg at each end, while others reply on the other end of the pump being wedged into the V formed by the top tube and seat tube.

enter image description here

enter image description here

protected by Gary.Ray Sep 5 '14 at 13:36

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