As time went on, the Bicycle Glossary has grown, and many of the pages became inconveniently large.
I have split the larger pages into smaller ones, but I realize that there may be external links pointing to the older pages. For this reason, I have maintained copies of the older pages at the same location.
This is one of the older pages, and the newer pages that were derived from it are liable to be more complete and up to date, so please follow the links below to the current version. Sorry for any inconvenience.
If one of my own pages had a link that took you to this page, it would be helpful if you would send me an email with the URL of the page that had the bad link, so I can update it.
Sheldon Brown
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- An idler is a pulley or roller that does not produce any mechanical advantage, nor transmit power to a shaft. Idlers are used to lead a chain around a bend (as in short wheel base recumbents), or to take up slack in a drive chain (as in a tandem chain tensioner, or the pulleys in a derailer
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- Interactive Glide is an extension of Hyperglide, in which both sides of the sprockets are contoured to improve upshifting.
I.G. sprockets are very slightly thicker than Hyperglide ones, and some Shimano Hyperglide chains may hang up if used on an I.G. cassette. The slightly wider I.G. chains work on either type, as do SRAM chains.
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- Indexed shifting means that the shift control has positive detents or click stops that provide discrete positions corresponding to different gears. See friction shifting
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- Sturmey-Archer term for the small chain and shaft which fit into the axle and connect the shift cable to the internal parts of many internal geared hubs.
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- Internal gearing:
Gear systems in which the gear shifting mechanism is built into the hub of the rear wheel. This is usually accomplished by the use of planetary gears.
The most widely known form of internal gearing is the three-speed utility bicycle. 4-and 5-speed hubs have also been available for many years, but have been out of fashion since the early '70's bike boom. Recently, Shimano and Sachs have started marketing 7-speed hubs, and Sachs is reported to be testing a 12-speed model.
Internal gearing is usually heavier and more expensive than derailer gearing. Bicycles with internal gearing usually have fewer speeds than comparable bicycles with derailer gears, and the mechanical efficiency is sometimes less with internal gearing.
Internal gears are generally more reliable than derailer gears, especially for bicycles which are used in wet or dirty conditions, because the gear mechanism is all contained within the rear hub, out of harms way. The other great advantage of internal gears is that they can be shifted even when the bicycle is at a stop. This feature makes them particulary suitbable for use in stop-and-go city traffic.
Not all internal gears are built into the rear hub, there are also models that are built into the bottom bracket.
Internal gears may also be combined with derailers to produce "hybrid" gearing
Internal cable routing:
The practice of running gear or brake cables through the inside of a frame, instead of outside. This is usually done for the sake of making the bike look nicer. Unfortunately, internal cable routing usually degrades performance by increasing weight and cable friction. It can also make servicing the bicycle more difficult.
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- An "inverted tread" is like the tread of most car tires, where the tread area may be visualized as a solid mass of rubber with grooves cut into it. "Knobby" tread would be seen as a tire with thin rubber over the casing, but with knobs stuck on here and there.
Since tires are made by moulding, not by cutting or sticking tread features on, this distinction is somewhat theoretical, and some tires have characteristics of both types.
"Inverted" tread tires typically have a more continuous contact area with the riding surface, so they give a smoother ride on pavement than knobby treads do. They can also give a better grip on loose, uneven surfaces than smooth tires do. They are mainly used as a compromise on- off- road tire. They don't grip as well in sand and mud as serious knobbies, and they are heavier and have more rolling resistance than smooth tires intended for paved surfaces.
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- Investment casting or "lost wax" casting permits casting of complicated shapes by using single-use plaster moulds that can be broken apart to free the cast part from the mould. This is an expensive process used mainly for high quality lugs and fork crowns.
This process is explained in detail at: http://users.lanminds.com/~drewid/Lost%20Wax%20Casting%20.html
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- Italian bicycles are built to specific standards of threading and dimension. Most parts on Italian dimension bicycles are interchangeable with British/ISO dimensioned parts.
The major exception is the bottom bracket. Italian bottom brackets are 70 mm wide, as opposed to the usual 68 mm dimension of British/ISO and French bottom brackets. The cup diameter is also larger. Sometimes, bicycles which have damaged bottom-bracket threads are machined out to Italian size to eliminate the damaged threads. Italian bottom brackets, like the French, use a right-hand thread on both sides, so the fixed cup is prone to loosening up unless very securely tightened.
Italian threading is a curious mixture of metric and British. Diameters are specified in millimeters, but threads are in threads-per-inch! In addition, the thread angle is 55 degrees, like the obsolete British Whitworth system, rather than 60 degrees as with U.S. and metric threads.
Italian freewheel and headset threads are the same as British/ISO, except for the thread angle difference. They may be interchanged, but you should not go back-and-forth bewteen Italian and British/ISO headsets. Italian freewheels are basically extinct, so the issue is moot there.
Italian size handlebars/stems generally use a clamping diameter of 26 mm. Many high-end aftermarket drop handlebars and "road" stems also use this size even if not Italian made.
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- The International Organization for Standardization. This is an international agency that is active in trying to rationalize bicycle design to make parts interchange more easily among bicycles made in different countries. Most ISO standards are compatible with British standards. These standards include:
In the case of tires and rims, the ISO adopted the E.T.R.T.O. system, the modern system for designating tire and rim sizes. This is explained in detail in my article on Tire Sizing
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- A thin lock nut.
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- Less expensive Japanese bicycles use J.I.S. sized headsets, better ones use Campagnolo-sized headsets. Frames and forks built for J.I.S. headsets can be machined to fit standard Campagnolo-type headsets.
J.I.S. fork crown seats are 27 mm in diameter, instead of 26.4 mm
J.I.S. head tube inside diameter is 30 mm, instead of 30.2mm
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- The upper pulley on a rear derailer. This is the pulley that actually guides the chain from one sprocket to another. Shimano jockey pulleys are designed with a "Centeron®" mechanism that allows a small amount of sidewards motion to compensate for imprecise index adjustment.
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- Industry slang for "Just Riding Along." Refers to disingenuous customers making questionable warranty claims, as in "I was just riding along when suddenly my fork bent backwards."
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- African-American term for "derailer".
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- See "Kidback."
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- One of my favorite French puns. The letter "K" is pronounced "kah", the number "7" is "sept" (the "p" is silent, like the "p" in swimming.) Thus, "K-7" is "kah-sept" or "cassette." I first encountered this in a French electronics catalogue, and it took me quite a while to figure it out. As far as I know, the French only use this abbreviation for tape cassettes, but I have fallen into the habit of using it as a shorthand for freehub cassettes.
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- The large tube at the bottom of a tandem frame that runs between the two bottom brackets. Also known as "boom tube."
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- A popular Japanese form of track racing. Keirin races are partially paced by motorcycles. This is one of the few human athletic events at which pari-mutuel betting is legal.
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- A very strong artificial fiber, used in bullet-proof vests and bicycle tires. Kevlar is used in tires two different ways, for two different purposes:
- Kevlar beads are used on some high performance tires. Replacing the normal wire bead with Kevlar ® saves about 50 grams per tire. Kevlar-bead tires have the additional advantage of being foldable, making them popular as emergency spare tires with touring cyclists. Kevlar-bead tires are somewhat harder to mount on a rim, and are more likely to blow off than wire-bead tires. They work best on "hook edge" rims.
- Kevlar-belted tires have a layer of kevlar under the tread surface, with the purpose of making the tire more resistant to punctures caused by small sharp objects, such as thorns and glass slivers. Kevlar-belted tires have slightly higher rolling resistance, price and weight than corresponding tires without the belt.
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- In British usage, "key" is often used as a synonym for what an American would call a wrench. Even in the U.S., the term "Allen key" is sometimes used for an Allen wrench
"Key spoke" is a term I coined to designate the first spoke installed when building a new wheel.
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- A keyed washer is a washer with a special-shaped hole that fits over a special shaft. It can slide, but not turn. The usual set up is to have a groove in the axle or shaft, and a washer's hole will have a small tang that fits into the groove. This is almost always used in headset and pedal bearings. It used to be common in hub bearings as well, but has fallen out of favor for that application.
Another type of keyed washer fits a shaft that is round but has one (or more) flat side(s). French forks usually use this system, with a simple filed flat on the back of the steerer.
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- A two speed coaster brake hub, which switches between its two gears each time the brake is applied. The advantage of this system is that it doesn't require any hand controls or cables. They were formerly made by Bendix and Sachs, and were popular on folding bicycles and inexpensive tandems, but are not currently in production.
Bendix (U.S. company) made 3 models, distinguished by colored stripes running around middle of the hub shell.
- The "blue band" model offered direct drive plus a higher gear.
- The "yellow band" and "red band" flavors offered direct drive plus a lower gear. The difference between the yellow and red models is in the brake. The red band had a disc-type brake, like the old New Departure coaster brakes, while the yellow band used a pair of brass shoes pressing against the inside of the shell, as with newer Bendix and other "modern" coaster brakes.
Note that the sprockets are not interchangeable on these hubs, they only took a 20 tooth sprocket.
Sachs/Torpedo (West Germany) also used to make a kick-back hub. These are most commonly found on folding/take-apart bikes, where they offer the advantage of not requiring any cables to run from the front to the rear of the bike.
The Sachs/Torpedo hub, unlike the Bendix, did allow sprocket interchangeability, using the same 3-splined sprockets used by most other multispeed hubs (Sturmey-Archer, Shimano SRAM/Sachs, etc.) These are available from 13-24 teeth. The Sachs/Torpedo unit is also quite a lot smaller than the Bendix models.
Kickstand
- A prop for holding a bicycle upright when it is parked. They are called kickstands because they are operated by the foot.
Kidback
- An adjustable "bottom bracket" which clamps on to the rear seat tube of a tandem to permit a child ("stokid") who cannot reach the normal stoker pedals to pedal.
Kit
- A set of all the parts needed to turn a frame into a ready-to-ride bicycle. See "group."
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- Wheel sucker. Term popular with tandemists, generally refers to solo cyclists who draft tandems.
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- A tire with an "aggressive" tread pattern, that is, one with knobs or bumps of various shapes, designed to dig into soft surfaces for better traction. Knobby tires get better traction on soft surfaces such as mud, gravel, snow, and dirt, compared with smooth treaded tires.
Knobby tires perform extremely badly on paved surfaces. The knobs greatly increase rolling resistance, and create annoying vibrations. They also corner badly on pavement, due to squirm.
K.O.P.S. (Knee Over Pedal Spindle)
- This refers to a popular fitting theory that states: When the cranks are horizontal, a plumb line straight down from the front of the rider's front knee should intersect the spindle of the pedal. This condition is achieved by adjusting the front/back position of the saddle.
This approach is quite popular with racing coaches, but it is by no means clear that this is a good setup for general cycling. Many recreational riders prefer a more rearward saddle position than this, with the extreme case being the recumbent position.
Some triathletes
and time trialists
prefer a more forward position. This is generally an approach that is used with æro type handlebars
and arm rests.
See also Keith Bontrager's article "The Myth of K.O.P.S."
and my article on Frame Sizing
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- A unit of pressure, equal to .01 BAR or .145 PSI.
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- Schwinn trademark for a family of wheelie bikes. These have become quite valuable to collectors.
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- In the Victorian era, when the bicycle had its first popularity, women were forced to wear long skirts, which prevented them from riding conventional diamond-frame bicycles. This led to the development of the "lady's bicycle" which eliminated the top tube from the frame, adding a second down tube for strength.
Since hardly anybody rides in a skirt anymore, this inferior design is pretty-much obsolete. Conventional diamond frames have several advantages over the Victorian lady's bicycle. They are:
- Lighter
- Stiffer
- Stronger
- Easier to pick up and carry over stairs, etc.
- Roomier, to mount useful accessories: bottles, pumps, locks, etc.
See also "mixte."
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- Thin tubes that run in pairs alongside the front part of a frame, and typically extend past the seat tube to the rear fork ends. These are most commonly seen on mixte frames and on older tandems, although they are also used on a few large-sized diamond frames intended for heavy-duty use.
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- Because some bicycle users are competent enough to remove their front wheels but not competent enough to secure them properly when they reinstall them, virtually all new bike purchasers have been deprived of the handy function of quick-release front wheels.
This has been done by encumbering fork ends with extra hardware, ridges or lumps that keep the wheel sort-of attached even if it has been installed by someone who doesn't know what he or she is doing. Unfortunately, this means that the quick-release mechanism must be re-adjusted each time it is used, seriously slowing down the operation.
Since this extra stuff was installed as a defense against frivolous lawsuits by ambulance-chasing shysters, the extra bumps are sometimes known as "lawyer lips" or "lawyer tabs."
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- Most threaded fasteners are right threaded, so you turn them clockwise to tighten them. Some parts which are used in conjuction with rotating shafts would tend to unscrew themselves if they threaded normally, so they are threaded in the opposite direction. This is called a "left thread," "left hand thread" or "reverse thread."
Left-threaded fasteners are turned counter-clockwise to tighten them.
Left threads are found on left pedals, some bottom-bracket parts, and internal parts of freewheels.
Spoke nipples and the expander bolts that hold bar-con shifters in place often appear to have left threads, because they are approached from the opposite direction of most fasteners.
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- Large flange or Low flange (hub). This is a source of confusion, since these two meanings are opposite. For clarity, this abbreviation should be avoided.
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- Traditional U.S. bicycle industry term for bicycles with tires narrower than about 1.5".
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- The limit stops are two screws that set the limits of how far the derailer can move from left to right. They are usually located on the back of the parallelogram, sometimes they face outward to the bicycle's right. The ends of the screws bump into internal parts of the parallelogram when the derailer has moved all the way in the direction controlled by that screw.
See my article on Derailer Adjustment for more details.
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- Another term for a direct-pull brake.
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- A nut which is tightened against another nut to keep it from loosening up. Often, but not always, there will be a key washer between the lock nut and the cone or other part it secures.
Lock nuts are used to secure bearing adjustment of most hubs, headsets, pedals and sidepull brakes.
Most hubs use lock nuts to secure the cones so that they will stay in adjustment. These lock nuts are the outermost parts which are screwed onto the axle, and their outer surfaces press against the insides of the fork ends of the frame. The lock nuts are therefore the reference point by which axle width and dishing are measured.
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- A thin lock nut used to keep threaded assembly from coming unscrewed. Conventional bottom brackets use a lock ring on the adjustable cup to make it hold its adjustment.
Fixed-Gear (Track) Hub Lockring Threading (Left-hand thread):
| English/ISO | 1.29" x 24 TPI
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| Campagnolo/Phil Wood | 1.32" x 24 TPI |
| Old French | 33 mm x 1.0 mm |
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- ******
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- ******
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- See investment casting.
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- A low gear is one in which the pedals move rapidly compared to the speed of the wheels.
Low gears are achieved by using small chainwheels and large rear sprockets.
Low gears are used for climbing hills, or for starting up from a stop.
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- Modern derailers are spring loaded, pulled one way by the spring and the other way by the control cable. A "low-normal" derailer is one in which the spring pulls it toward the lower gear(s). If you release the tension on the cable, it will shift to the lowest gear.
Up until the late 1950s, all spring loaded derailers were low-normal type. When Campagnolo introduced the parallelogram-type rear derailer, they changed to high-normal, and most rear derailers made since then have been of the high-normal type.
The major advantage of high-normal rear derailers is that, when used with a low-normal front, both levers move in the same direction for double shifts. This makes it easier to perform a double shift with down-tube shift levers.
The major advantage of low-normal derailers is that they generally downshift a bit better than high-normal units.
In the late 1990s, Shimano
attempted to revive the low-normal rear derailer design, using the trademark "RapidRise." This has met with limited acceptance.
Sun Tour
used to make high-normal front derailers. The principal advantage of this was that the front and rear shift levers moved in the same direction to either raise or lower the gear, which was less confusing for beginner cyclists.
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- Lowrider racks are front pannier racks designed so that the panniers attach below the top of the front wheel, so that their center of gravity is low and close to the steering axis of the fork.
- Lowrider bicycles are a fad design of bicycles, inspired by the wheelie bikes of the 1960's with very long wheelbases. They are built purely as an exercise in styling, with no real concern for riding qualities. Some of them, in fact, are not rideable, because the cranks are so close to the ground that the pedals cannot turn around. They commonly feature lots of chrome or gold plating, 72 spoke wheels, sometimes steering wheels instead of normal handlebars, and springer forks. These toy "bicycles" should not be confused with recumbents, which are real bicycles.
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- A lug is a socket that forms the junction between two or more frame tubes. Traditional bicycle construction uses steel tubes and lugs, joined together by brazing or silver soldering so that the space between the tube and the lug fills up with molten brass or silver alloy. Some aluminum or carbon fiber bicycles also use lugs, with glue instead of the brass or silver.
Some frames use internal lugs, with a necked-down section that fits inside of the tube, rather than having a socket that the tube fits into.
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- A shiny, stretchy fabric, popular for cycling clothing. The stretchiness of Lycra allows it to snugly so that it doesn't flap in the breeze, while still allowing free motion of the legs.
Lycra is also sometimes used as a covering for plastic/foam saddles, but it is rather fragile for this application.
