Terminology index - a list of bike part names and cycling concepts

Question

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):

A mountain bike has the following parts (source):

---

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

Answer 1

Bicycle-Shaped Object (BSO)

A derogatory term for a very cheaply produced bike with very low quality components. The components can be hard to maintain due to poor tolerances. BSOs are often sold at non-specialty retail stores.

The etymology of the term is uncertain. It appears in use in some parts of the English-speaking world. It may originate in the UK, as discussed at the link. Other languages may use terms equivalent to supermarket bike or department store bike. These terms are likely to be understood in English as well.

For instance the BSO pictured is being sold in the UK by ASDA (owned by Walmart) for £75. These bikes tend to be mass produced and sold in flat pack boxes for self-assembly.

Purchasers of lower-end bicycles tend to be less experienced cyclists who focus on price. Many BSOs carry features which are included for marketing purposes but are unnecessary for the typical end-user. Such features may include front and rear suspension, wide off-road style tyres and an excessive number of gear ratios. For cyclists who are riding on city streets or smooth trails, these features are unnecessary. Including these features reduces the budget available for better components elsewhere.

It is more advisable to search for a cheap second-hand bike in a similar price range from a more experienced cyclist or on eBay than to go for one of these.

Answer 2

Door Zone

The area next to parked cars that a suddenly opened door would cover. A hazard that you should avoid.

Satirical portrayal of Santa Monica bike lane design; it illustrates the "door zone" concept well.

Cycling in the Door Zone reduces your ability to react to hazards emerging from the space between parked vehicles. These may include unobservant pedestrians, inadequately restrained dogs (whose leads can reduce your options), sports equipment and children chasing sports equipment.

Drivers entering the road from a driveway, forecourt or junction are less likely to observe a cyclist who is not occupying the space where oncoming motor vehicles are expected to be observed. This contributes to the SMIDSY(Sorry mate, I didn't see you) phenomenon.

Answer 3

Presta Valve / Presta Tube

aka Sclaverand valve or French valve

photo credit

The Presta valve is a valve commonly found in high pressure road style and many mountain bicycle inner tubes. The air pressure in an inflated tire holds the inner valve body shut. A small screw and captive nut on the top of the valve body permits the valve to be screwed shut and ensure that it remains tightly closed. The nut must be unscrewed to permit airflow in either direction (this must be done before attaching a pump). The screw remains captive on the valve body even when unscrewed fully; it is tightened again after the tire is inflated and the pump removed.

A Presta valve adapter can be used to fill a Presta tube with a normal Schrader-style air pump, although many pumps today come with a built-in adapter.

For a video tutorial on the use of the adapter, check out this video at BicycleTutor.com

More information: Presta valve (Wikipedia).

Go to Schrader valve.

Answer 4

LBS

LBS is the acronym commonly used for Local Bike Shop. The term is usually used when comparing small, privately owned shops with large chains, big box stores, and internet shops.

The best local bike shops usually have trained staff who have many years of experience in selling, maintaining, and repairing bicycles and have a well-equipped repair workshop. They can special order parts and let you know if a modification you want to make will work -- and how to make it work. As with all things, local bike shops vary in terms of their experience (and attitude) and it pays to shop around to find a LBS that matches your interests and orientation.

Large department or chain stores, on the other hand, often sell BSOs that they assemble using staff who often have little to no background in bicycle mechanics. They cannot repair or maintain the BSOs they sell and your only recourse often is to just return the bicycle if it is still under warranty.

http://www.flickr.com/photos/johnprolly/5728618798/

Answer 5

Cadence

Cadence is the number of revolutions of the crank per minute.

Cyclists typically have a preferred cadence at which they feel most comfortable, and on bicycles with many gears it is possible to stick to a favourite cadence at a wide range of speeds. Recreational and utility cyclists typically cycle around 60–80 rpm; racing cyclists around 80–120 rpm and sprinters up to 170 rpm for short bursts. The professional racing cyclist and Tour de France champion Lance Armstrong is known for his technique of keeping up high cadences of around 110 rpm for hours on end to improve efficiency¹

¹ http://en.wikipedia.org/wiki/Cadence_(cycling)

If you are getting pain in your knees, it could be that your cadence is too low. A cadence between 80-100 will probably reduce knee pains, as stated in bicycling.com or more detailed at Cycling Performance Tips web site.

EDIT by Ivor

To answer a comment below on beginners and cadence...

Cadence is critical to enjoying your cycling and if you become involved in cycle racing, winning. Cadence is something that is learned and once learned you promptly forget about it and move onto getting other things right :)

For a beginner:

1. Get to know your gears.
   • Drop it into a high gear (big chainring on the front, small cog on the back)
   • Feel how hard it is to push (Pay attention to where you feel the muscles working)
   • Drop it into a low gear (smallest chainring on the front, largest cog on the back)
   • Feel how free your legs spin (Pay attention to how you bounce in the saddle :) If you are bouncing, then you are spinning too much, i.e. your cadence is too high)
   • Find a combination of gears that allow you to spin your pedals without feeling undue pain in your muscles and doesn't make you feel out of breath. (Ignore the speed for the moment)
   • Get to know this "sweet spot", ride around in this gear for a while and adjust your gears to suit your speed so that you balance not being out of breath and over exertion. (Watch out for the bounce in the saddle :) )
2. The next thing to take into account is how fast you want to go
   • Without a bike computer? - Your feeling of relative speed is good enough
   • With a bike computer? - Set a reasonable target, say 20 km/h
   • Using the gears you have selected for your sweet spot, try to hit your target speed.
   • Once you hit it, can you keep it going? For how long? - Set a reasonable target say 5 mins.
   • When you have finished this, where does it hurt?
   • In your chest? Out of breath big time? - You may have been spinning too much, i.e. your cadence was too high?
   • Muscles in the small of your back, quads, glutes, knees, calves groaning or hurting (not burning, burning isn't as bad as you think) - You may have been spinning too little i.e. your cadence was too low?
3. There is an ideal cadence proposed by some sports physiologists that is somewhere between 80 to 100 turns of the pedal per minute (rpm)
   • The only way to know your cadence accurately is to have a cadence enabled bike computer and sensor.
   • The other way is to know your gear ratios (Check out BikeCalc.com)
   • For example, You are riding your bike, it has a wheel of size 700c/29 and a tyre that is 23 mm wide, with a front chainring of 34 teeth, a rear cog of 17 and you are pedalling at a speed of 20 km/h. You should then have a cadence of 79 rpm. Simples :) (Get the bike computer ;) )
4. Get used to spinning your legs in that range of RPM, i.e. 80 to 100 rpm.
   • In all conditions, on any terrain, whatever the occasion.
   • It trains your heart and body to be cardio fit and with a stronger heart comes better stamina and greater strength.
   • Pick up the pace and work to get the legs spinning at the next level of speed.
   • Hard work and worth it.
5. Go cycling with a group more experienced than you
   • Watch them as they cycle, see all of the different styles and high cadence
   • Listen to the experienced guys as they can advise on many many things.
6. Enjoy it, you will have earned it :)

Answer 6

Clipless pedals a.k.a. clip-in or step-in pedals

Clipless pedals require a special cleated cycling shoe that locks itself into the pedal's surface. To release a foot/shoe from a clipless pedal, the rider typically twists his/her foot outwards.

The word "clipless" (a rather confusing term) refers to a pedal not having an older style toe clip straps.

LOOK Pedals

LOOK pedals came first and were inspired by ski bindings. LOOK pedals are commonly used on road bikes. A similar (but incompatible) pedal system is Shimano's SPD-SL system.

SPD Pedals

Shimano Pedaling Dynamics or SPD pedals use a cleat that is recessed into the shoe. This allows the rider to walk normally, which is why this pedal is commonly used in mountain biking or similar disciplines, where a rider may need to walk for short distances over some obstacles. Note that Shimano's SPD-SL system is not compatible with SPD.

Cleats used for these pedals have two holes for screws that go into a shoe.

SPD-SL

A type of clipless pedal, cleats and compatible shoes used mostly by road race cyclists.

Compared to SPD, this system has bigger cleats which protrude from shoes, making walking in them awkward. Cleats for SPD-SL have three holes.

SpeedPlay Pedals

Design proprietary to Speedplay products. The spring retention and release mechanism in this design is bolted to the shoe, rather than part of the pedal.

Crank Brothers 'Eggbeaters' system

A proprietary design that uses proprietary cleats. Used by Crankbrothers in all their clipless pedals. The most prominent example is the Eggbeaters model range looking very minimalistic.

Toe Clips a.k.a "Rat trap"

Clipless pedals are called so, even though you do clip onto them — because one avoids the need for toe clips and straps.

The word "clipless" (a rather confusing term) refers to a pedal not having these older style toe clip straps.

---

This answer draws heavily from Clipless pedals (Wikipedia).

Answer 7

Fixed Gear or Fixed Wheel

AKA: Fixie

A fixed-gear bicycle has the rear gear locked to the hub, which fixes the pedals rotation to the rear wheels rotation. In other words, you can't coast; the pedals are always in motion as long as the bike is. Track bikes are commonly fixed-gear.

The sprocket is screwed directly onto a fixed hub. When the rear wheel turns, the pedals turn in the same direction. This allows a cyclist to stop without using a brake, by resisting the rotation of the cranks, and also to ride in reverse.

Fixed-gear bikes are almost always single-speed (i.e. have only a single gear ratio), but internal-gear hubs without freewheels do exist.

The hub in the picture is a flip-flop hub.

More information: http://en.wikipedia.org/wiki/Fixed_gear

Compare with Single Speed.

Answer 8

Schrader valve/Schrader tube

aka "American valve" or "car valve"

The Schrader valve consists of a valve stem into which a valve core is threaded, and is used on virtually all automobile tires and most wider rimmed bicycle tires. The valve core is a poppet valve assisted by a spring.

A valve cap is important on a Schrader valve because if one is not fitted, dirt and water can enter the outside of the valve, potentially jamming it or contaminating the sealing surfaces and causing a leak. Rock salt and other chemical deicers used in the winter are especially damaging for the brass components in the Schrader valve.

Schrader valves are almost universal on car tires, meaning you can often (carefully) inflate your bike tires with the air machines at roadside garages.

For an instruction video on patching and inflating a Schrader tube, check out this video on BicycleTutor.com.

More information: http://en.wikipedia.org/wiki/Schrader_valve
Go to Presta Valve

Answer 9

Pannier

A pannier, pronounced pan-yer /ˈpanyər, ˈpanēər/ (US) or pan-i-er /ˈpanɪə/ (UK) ^[1], is a bag designed to be mounted on the side of a bicycle rack. Bags can be made of nylon, canvas, or waterproof materials such as PVC. Rear is most common, but smaller panniers intended for a front rack are also available.

Often erroneously called a saddlebag because a pannier on a motorcycle or horse is attached to the saddle. On a bicycle, the saddlebag mounts behind the rider from loops at the back of the saddle. The saddle bag goes athwartship – from side to side.

Answer 10

Flip-Flop Hub

Most often seen on fixed gear track (velodrome) bikes, a flip flop hub is hub that allows a cog to be attached to each side.

This allows a rider of a fixed gear bike to effectively 'change' gears by taking the rear wheel off, flipping it around and reattaching the wheel.

Track riders will use this to have a smaller (more teeth, fewer gear inches) warmup gear that allows them to spin at a higher cadence and a larger (fewer teeth, more gear inches) cog for racing or high speed efforts.

Variations of flip-flop hubs might offer a freewheel in one direction and a fixed gear in the other, so a cyclist can convert the bike from a single-speed to a fixed gear bike by flipping the rear wheel around.

The unused cog is an additional hazard. Many velodromes require unused cogs to be removed. A collision involving a bike carrying an unused cog at the 2013 North America Harcourt Bicycle Polo Championships led to an amendment of the NAH ruleset to explicitly identify exposed unused cogs as a prohibited hazard. Players are permitted to carry an unused cog if it is covered.

For a fixed-gear road cyclist, a flip-flop hub often is used to allow one side as a fixed gear, and the other side to freewheel. This way, a tired fixie rider can switch to freewheeling (possibly with a different ratio) and get home.

More information: http://en.wikipedia.org/wiki/Flip-flop_hub

Answer 11

Quick-release

Quick release skewers (sometimes abbreviated QR, sometimes just called skewers) secure bicycle wheels in the dropouts. They have a lever that when opened, enables the wheel to be removed quickly and without additional tools. They use a cam mechanism at the lever end pulling against a threaded nut at the other end. The cam mechanism may be internal or external; the latter type is cheaper to produce and is often lighter, but it produces lower clamping force for the same amount of hand pressure on the QR lever.

_{Quick-release axle (internal cam)}

Their invention is frequently attributed to Tullio Campagnolo, but Jan Heine's research shows this may be inaccurate. Heine was unable to determine who invented the QR, as there appears to be no original patent for the QR mechanism.

Tabs called lawyer lips frequently come on fork and/or frame dropouts. They prevent the wheel from dropping out immediately when the QR lever comes open, the nut must be unthreaded several turns as well. These tabs increase the amount of time needed to operate a QR but they can be an important safeguard against improper operation of a QR.

Wheels with disc brakes may be secured by QRs or by thru axles. Disc brakes are said to generate much greater torque than rim brakes; some experts contend that disc brakes can eject wheels from dropouts. Thus, increasingly disc brake bikes and wheels are secured by thru axles rather than QRs.

QRs are sometimes used on seatpost clamps as well, to allow easy adjustment of the saddle height. "Quick-release" also refers to several other types of quick-release mechanisms that are popular on folding bicycles, such as collapsible seatposts and folding frames.

Answer 12

Triathlon bars or Aerobars

Aerodynamic bike handlebars are for racing bicycles and particularly time trial bicycles.

Included are narrow, bolt-on extensions that draw the body forward into a tucked position, pursuit bars that spread the arms of the rider but drops the torso into a slightly lower position, and integrated units that combine elements of both designs.

Triathlon bars are commonly used in triathlons and time trial events on road and track. However, they are illegal in most mass start road races or any other event where drafting is permitted because, while aerodynamically advantageous, they tend to draw the hands away from brakes, make the rider slightly more unstable on the bike, and can be dangerous in the event of an accident. Further, they are not useful in sprints or shorter climbs where power is of greater importance than aerodynamics.

There is a distinct set of aerobars that are utilised in draft legal triathlons on regular road frames. As draft legal (ITU sanctioned) triathlon races require road frames that are UCI legal, a stubby pair of arms has been developed for this style of racing.

Sources:

• http://en.wikipedia.org/wiki/Bicycle_handlebar#Triathlon_or_aero

• http://www.beginnertriathlete.com/cms/article-detail.asp?articleid=1414

Answer 13

Dunlop Valve

aka Woods valve or English valve

The Dunlop valve is an older style valve that is no longer commonly found in the english speaking world. It is still commonly found in Japan and the Netherlands on non-speciality bicycles. The advantage of a Dunlop valve is that it is very easy to manufacture. The main pressure control mechanism is a simple rubber tube called a "plug" or "worm" that can be easily replaced. However, the rubber plugs also quickly degrade and this can be a cause of frustration for users. Recent Dunlop valves in Japan come with mechanical springs rather than plugs.

A pump designed for a Presta valve can be used to fill a tube with a Dunlop valve.

More information: Dunlop valve (Wikipedia).

Go to Presta valve.
Go to Schrader valve.

Also see this answer.

Answer 14

Tire Lever

aka Tire Iron

A tire lever is a small, narrow lever used to help lift a tire off a rim. Traditionally they were steel, later aluminium alloy and now most commonly they are plastic.

The most important feature of a tire lever is that it does not have any sharp edges that may "pinch" the tube (that is, become wedged between the tube and the tire) causing a small hole or tear in the tube.
Operation of tire levers usually involves either a pair or a triple set of levers. Levers can also be used help get a tire onto a rim when it is a particularly tight fit.

More information: http://en.wikipedia.org/wiki/Tire_iron

Answer 15

Stem

Attaches the handlebars to the bike, or, more precisely, to the steerer tube. Stems are designed differently for different headset types (i.e. threaded or threadless). They are also sized to suit different diameter handlebars and in the case of threadless setups, different diameter steerer tubes.

Stems of many different lengths and angles are available, so that the rider can position the handlebars where they will be the most comfortable. There are also angle-adjustable stems made, so the rider may change bar positions without removing the handlebars or changing the stem.

More information at Sheldon Brown's site

Adjustable stem on a touring bike, attached to the headset with risers, with the handlebars removed

Answer 16

Chain Tool or Chain Breaker

Used to 'break' a chain by punching out one of the link pins. Needed to shorten a new chain to the correct length or to replace a broken link.

A chain link is placed in the open slot and the handle turned to force a punch pin into the pin of the chain, pushing it out of the other side.

Traditionally the tool needed to be used quite carefully such that the pin would not pushed all the way out, as the same pin was later used to reassemble the chain, using the same tool. Obviously, if a chain is repeatedly "broken" and reassembled this way at the same link the pin and associated holes in the plates will wear and no longer hold well, so care must be taken to not do this.

More recently this strategy has changed somewhat. Shimano now supplies special replacement pins which are equipped with a break-off guide cone on one end, making it easier to reassemble the chain. (Even with this scheme one should still avoid repeatedly "breaking" and reassembling the chain at the same link, though.)

Several other manufacturers now sell what is commonly called a master link (or quick link), which allows a chain to be reassembled without tools.

Answer 17

Bearing

A bearing is an interface between parts that turn and parts that do not. They enable an axle or other part to roll on steel balls. The hubs in the wheels contain bearings, as do the bottom bracket, the headset in the head tube, and the pedals.

• Sheldon Brown on bearings.

A standard bicycle wheel bearing consists of an axle, a hub, two cones, two locknuts, and a number of steel balls. In both ends of the axle is a concave section known as the "cup" that the balls sit in. The "cone", threaded onto the axle, contacts the balls from the other side, and together the cup and cone retain the balls and serve as the surfaces against which the balls roll. The picture above shows a cup and cone bearing assembly.

The locknut secures the cone so that it doesn't thread in or out as the hub turns relative to the (stationary) axle.

The bearings in the bottom bracket and headset are similar except that the cup part is stationary and the axle turns.

Bearings are also available in cartridge form, where the bearing cup with bearings inside is sold as a unit. The cartridge is then pressed into a seat in the appropriate part, e.g. the bike's bottom bracket assembly or the hub.

Many bearing assemblies have some level of sealing, which reduces the amount of dirt or water that get into the bearings. In general, the more tightly sealed the bearing, the more drag it will have and the more power it will take to turn the attached axle.

Bearings require periodic maintenance, typically cleaning and regreasing. Cartridge bearings are often replaced entirely, although they can be maintained as well.

The ball bearings and the races they turn on may be made of ceramic. Ceramic bearings have industrial applications in very rapidly rotating parts. On bikes, they likely reduce drag very slightly, but they are very expensive.

Answer 18

Gear Inches

One of the several ways to describe gearing; how hard/easy the bike is to pedal. The actual figure is the equivalent diameter of the wheel if you were on a direct pedal cycle like a unicycle or an old fashioned high-wheeler. It does allow for different size wheels as well as the gears, but it ignores the effect of different crank lengths.

Easier to pedal (granny-gears) have low gear inches (smaller equivalent wheel). Harder to pedal gears have higher gear inches.

The basic formula is:

GI = (CrT/CogT)*D
WHERE
GI     = Gear Inches
CrT    = Chain Ring Teeth
CogT   = Cog Teeth
D      = Wheel Diameter

For example, a 700c tire is going to have a diameter of roughly 26.3" (depends on the width of the tire). If you have shifted to your smallest front ring of 24 teeth, and your biggest rear cog of 27 teeth then your gear inches are:

GI = (24/27)*26.3 = 23.4"

Note: if you want to take the math a little further - and of course I do since I am a math nut - you can find how far you travel each pedal stroke by remembering that:

Circumference = pi*Diameter

In our example:

Circumference = 3.14*23.4" = 73.5

Note: you can search for Bicycle Gear Calculator and find several pages online that will do the math for you. There will be a lot of variation and calculators use different rounding and make different assumptions about wheel width. Pre-prepared tables are available, calculated for ETRTO 23-622 (700c x 23mm) tyres or in the case of traditional track racers' tables, a "standard" wheel with an assumed 27" overall diameter.

Answer 19

Chain Tug

AKA: Chain Tensioner

On most bikes, the rear derailleur keeps the chain in tension. On fixed gear, single speed, or hub geared bikes, a chain tensioner is required to keep the chain in tension. Without this mechanism, the chain may fall off, or the rear wheel may pull forward while pedaling.

Some chain tugs are available with derailleur hangers to allow horizontal droput bikes to run derailleur gearing systems.

More information about chain tugs is available in this answer.

Bottom Bracket mounted Chain Tensioners:
Typically seen on downhill styled mountain bikes.

Answer 20

Track pump (or floor pump)

A large pump that you use by standing on the bottom plate and moving the handle up and down. You can use both hands and your back to pump a high pressure tire quickly and easily. Generally for use at home - or at the track - rather than for carrying on the bike. Some manufacturers make portable track pumps which bolt to the down tube for easier inflation of high pressure tires.

Features to look for:

• sturdy construction
• pressure gauge
• a head that can be used with both Presta and Schrader valves

Answer 21

Derailleur hanger

The part of the bicycle frame that the rear derailleur bolts into. As in the pictures below, most derailleur hangars are separate pieces of metal, often aluminum, that bolt onto the dropout. These are called replaceable derailleur hangars.

Derailleur hangars frequently bend slightly if a bike is dropped or crashes, which is especially common off road. This can compromise shifting. The key advantage of a derailleur hangar that is softer than the frame is that in a crash, it will bend and break before the derailleur or the frame. The hangar can then be replaced. Replaceable hangars are proprietary to each frame and tend not to be interchangeable. Manufacturers will usually stock them as replacement parts. The US company Wheels Manufacturing makes a wide variety of replacement hangars also.

Non-replaceable derailleur hangars are part of the dropout, as in the picture below. (Note that this bike is set up and singlespeed, with a derailleur in place you would never put the axle this far forward in the dropout)

These hangars are present on some steel and titanium bikes. If the derailleur hangar is bent, it will need to be cold set (i.e. bent) back into alignment. Tool manufacturers make derailleur alignment gauges for this purpose. Steel and titanium hangars can be bent repeatedly. If a non-replaceable derailleur hangar breaks, an experienced welder (preferably a frame builder) will need to replace it.

Answer 22

Chain gauge

Measures the stretch of a chain to determine how worn it is and when to replace it.
It's made to fit exactly between two separated links of a standard chain.

Alternately you can measure the chain with a ruler - standard links are 1inch (25.4mm) long.

Note - the chain doesn't actually stretch, the pins connecting the links wear away making the joints looser. The extra movement reduces efficiency, causes the chain to skip and will wear the rear gear teeth.

Answer 23

Headset

The group of bearings and bearing cups that allows the steer tube to turn freely within the head tube. Headsets come in two basic varieties.

Threaded headsets are common on older bikes and inexpensive bikes. They are called "threaded" headsets because the top race is held on with a threaded race and locknut which thread onto a threaded portion of the steerer tube.

Threadless headsets are standard on modern mid-level and high-end bicycles. They are called "threadless" headsets because there are no threads on the race or steerer tube nor is there a lock ring. The headset is held together by pressure created by a bolt through the top cap which threads into a star nut inside the steerer tube.

Images courtesy of Sheldon Brown.

Answer 24

Groupset

A groupset or gruppo (from the Italian for "group") generally refers to the components involved in shifting gears, braking, and transmitting power from the rider's legs to the rear wheel. It excludes stems and handlebars (sometimes referred to as the cockpit of the bicycle), saddles, seatposts, pedals, and quick release skewers.

Groupsets typically include:

• integrated brake levers/shifters (on older bikes, brake levers and down-tube or bar-end shifters)
• front and rear brakes (including calipers/pads or rotors/disks/pads)
• rear derailleur
• front derailleur (unless the bike has a 1x drivetrain)
• bottom bracket
• crankset or chainset
• chain
• cassette (freewheel on older bikes)
• cables and housings as appropriate (for electronic groupsets, control wires and batteries)

In the past, groupsets have included some or all of the following components.

• headset
• hubs and usually quick release skewers
• stem and seatpost may have been included, or may have been optional purchases
• pedals are typically optional purchases

Shimano, SRAM, and Campagnolo account for the vast majority of road bike groupsets. SRAM had entered the road bike market in 1988, then exited, then re-entered in 2004. Shimano and SRAM are the majority of the mountain bike groupset market. Campagnolo briefly produced one mountain bike groupset before exiting that market. At the time of writing, Full Speed Ahead and Rotor have produced groupsets as well, but these have yet to achieve widespread take up.

Groupsets are offered at a range of price points. Each of the 3 major manufacturers makes one version for professional road (e.g. Campagnolo Super Record) or mountain bike racing (e.g. SRAM XX1). They also offer various lower level groupsets for consumers. Generally, the high-performance consumer groupsets (e.g. Shimano 105 and Ultegra) will have less exotic material (i.e. less titanium and carbon fiber) used in manufacture and will be heavier, but will usually offer very similar performance on other characteristics (e.g. durability, shift quality). Groupset manufacturers generally offer electronic shifting versions of their top two groupsets.

The original equipment manufacturer (OEM) market is dominated by Shimano and SRAM (i.e. most complete bicycles come with Shimano or SRAM components). For the most part, shifters and derailleurs are not compatible between brands, and complete bicycles will not mix these components. However, some complete bicycles will substitute cranksets and/or brakes from third party manufacturers for cost or performance reasons.

Answer 25

Handlebars

The part of the bike you hold onto. When you turn the handlebars, the front wheel turns with them. The front wheel is held in the fork, which ends in a steerer tube, which in turn attaches to the stem, which clamps onto the handlebar.

Broadly speaking, there are flat handlebars as found on mountain bikes and hybrid bikes, and drop handlebars which have bar ends that are curved below the flat portion. This question provides further detail.

Additional information:

Sheldon Brown on handlebars, drop bars, and upright bars.

Answer 26

Fender

Mudguard / mudflaps

A must for winter cycling. As the wheel rotates, it will spray water and dirt up a rider's back and onto various parts of the frame. Fenders block this spray. They are often recommended for riding in wet weather. Mudguards are flaps attached at the ends of a fender.

Commercial fenders can be made from metal or plastic. They can also be DIY'ed from plastic milk cartons. Typically, fenders require the frame and fork to have fender mounts. However, some fenders, like the ones depicted, can attach on to the frame and fork directly. This mounting is less secure, and such fenders do not cover as much of the wheel.

If an object like a stick gets jammed between the tire and fender, it can cause the fender to break off. The frame may be damaged as well. If there is not much clearance between the fender and tire, this may be an argument for using fenders made for race bikes. These fenders may just bolt to the seat stay and down tube, and will offer partial protection from dirt and water.

Answer 27

Bottom Bracket

The bottom bracket (BB) is an assembly that contains bearings and sometimes the axle that the cranks attach to. The bottom bracket shell is the part of the frame holding the bottom bracket.

Traditional bottom brackets screw into the bottom bracket shell, and contain both bearings and an axle. Axles/spindles can be square tapered (in two standards, JIS and ISO) or oversized (Shimano Hollowtech or ISIS). Generally, the oversized spindles were stiffer due to being larger, but had smaller bearings and may have had poorer bearing life. The crankarms were then fixed on to each side of the axle with retaining bolts.

In response to perceived issues with bearing life on oversize spindles, external bottom brackets were developed. Here, the bottom bracket assembly contains only the bearings, which are external to the frame. The bottom bracket cups thread into the shell. The crank axle is attached to one or both crankarms. The axle goes through the bottom bracket.

Alternatively, various press-fit bottom bracket standards were developed where the frame contains a seat for bearing cups. The BB cups, which contain bearings, are pressed directly into the frame. The crankset is then inserted as with external bottom brackets. There are numerous standards for press-fit bottom brackets. Cups for one standard are usually not interchangeable with a different standard. However, for each press fit BB standard, manufacturers will make cups to accept most or all cranksets on the market. Example open standards include BB86 and Press Fit 30. Some larger bike manufacturers have BB standards proprietary to their own frames.

For threaded BB shells, the most common threading standards are English, Italian, and T47. The last involves a much larger BB shell than the prior two standards.

Generally, users looking to install a BB and crankset from scratch would determine the frame's BB standard, then find a bottom bracket in that standard that matches their desired crankset. For replacing worn bearings on a threaded BB, users typically replace the entire BB. On press-fit BBs, users or bike stores can often extract and replace just the worn cartridge bearings from the cups.

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.

• Sheldon Brown on bottom brackets

Answer 28

Saddle

Also called the seat, the saddle is where the rider sits.

• Sheldon Brown on saddles.

Gel saddle

Leather saddle

Plastic saddle

Answer 29

Disc Hub

Disc hubs come in two varieties: 6-bolt ISO and Shimano's proprietary Centerlock spline. Converters exist to allow a Centerlock hub to accept a six-bolt disc rotor.

6-bolt ISO:

Shimano Centerlock: (Note, centerlock hubs ship with a rubber cover over the centerlock splines).

Answer 30

Hub Skewer

A replaceable part of a hub that attaches the hub/wheel assembly to the fork or frame. Some are equipped with a quick-release mechanism that allow removing the wheel without tools, facilitating changing a tire, putting a bike in the back seat of a car, etc. Unfortunately, the trade-off for easy wheel removal is that it's easier for thieves to remove a quick-release wheel.