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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- This refers to a wheel which is radially spoked on one flange, semi-tangent on the other.
For an explanation of this design, see my wheelbuilding article.
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- In the days of 4- and 5-speed freewheels, 8- and 10-speed bikes were commonly set up with chainwheels that were very close in size, for instance, 46/49, or 47/50. When used with typical freewheels of the era, the difference between the two front gears was about half as large as the difference between adjacent gears on the freewheel. (One reason for this was that early front derailers couldn't handle much more than a 3-tooth difference reliably!)
With half-step gearing, the larger shifts are made with the rear derailer, and the front is for fine tuning. This allows an 8- or 10-speed set up to have a reasonable range with fairly close spacing of the gears. One downside of half-step is that it uses all possible combinations, including those that run the chain at a fairly severe angle. This is not a big deal in an 8-speed rig, but is kind of marginal for 10-speeds. Another serious disadvantage is that every other shift in the normal sequence is a double shift (front and rear derailers simultaneously).
Half-step gearing is most suitable for riding in flat terrain, where shifting is rare. For bicycles with few speeds, it does allow finer gradations to get as close to the "ideal" gear for the particular wind conditions as possible.
Modern shift patterns use larger jumps on the chainwheels to select general ranges of gears, and fairly closely-spaced 7-or-more-speed clusters for the fine tuning. This greatly simplifies the shifting pattern, allowing constant adjustment to different grades in rolling terrain, with only occasional need for double shift.
Handlebar
- "Handle bars" on early bicycles were actually bars of solid steel. Solid handlebars became obsolete before the end of the 19th century; all modern handle "bars" are actually tubular, but the name persists.
Conventional handlebars are divided broadly into two styles: "drop" and "upright"
Handlebar grip
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Handlebar stem
- See stem
Handlebar tape
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- derailer, cable, chain, bottom bracket****
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- The bearing assembly that connects the front fork to the frame, and permits the fork to turn for steering and balancing.
The headset consists of four races plus associated parts:
- The crown race, which is pressed on to the bottom of the steerer, just above the crown.
- The lower head race is pressed into the bottom of the head tube.
- The upper head race is pressed into the top of the head tube.
- The adjustable race attaches to the steerer.
- Keyed washer and lock nut, forThreaded headsets.
or
Star fangled nut in the case of some threadless headsets.
| Size | Stem diameter | Crown race | Cup | Threads
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| Steerer O.D. | Steerer I.D. | Inside diameter | Outside diameter | per inch
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| BMX/ O.P.C. bikes | .833"(21.15 mm) | 26.4 | 32.7 | 24
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| French 25 mm (obsolete) | 22mm | 26.5, 27.0 | 30.2 | 25.4 (1mm)
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| 1" Standard (25.4 mm) | 7/8"(22.2mm) | 26.4 | 30.2 | 24
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| 1" J.I.S.(25.4 mm) | 7/8"(22.2mm) | 27.0 | 30.0 | 24
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| 1 1/8" (28.6 mm) | 1" (25.4 mm) | 30.0 mm | 34.0 mm | 26
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| 1 1/4" (31.8 mm) | 1 1/8" (28.6 mm) | 33.0 mm | 37.0 mm | 26
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- The front tube of the frame, through which the steerer passes. The length of the head tube gives a quick visual indication of frame size, because it varies more, proportionally, with frame size than any of the other tubes.
Helicomatic
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The Maillard Helicomatic hub was an early version of a cassette freehub. They came with a cute little pocket-size tool that incorporated a spline wrench for the cassette lockring, a spoke wrench, and a bottle opener. The Helicomatic was a nice idea on paper, but poorly executed. These hubs are losers.
Both hub flanges were 1mm farther to the left than those of a normal hub, causing increased dish in the rear wheel, and persistent spoke breaage problems. Many loyal Helicomatic fans tout the ease with which the cassette may be removed for spoke replacement as a great virtue, but if the hub were better designed, it wouldn't break so many spokes!
These hubs were prone to bearing problems as well. Due to clearance requirements, they couldn't fit the normal 9 1/4" bearing balls, so they used 13 5/32 balls on the right side. These didn't hold up well, and replacement cones are no longer avaialble to fit these hubs.
Hellenic stays
- A frame design in which the seat stays don't go to the seat cluster, but rather cross outside of the seat tube a few inches below the seat cluster, then go on to be attached to the top tube a few inches forward of the seat tube.
Hellenic stays have been used off-and-on since at least the 1930's by frame builders who wished to make their frames visually distinctive. It is of no practical value, and often causes un-necessary complication to brake cable routing, luggage rack attachment and installation of frame pumps. It is also slightly heavier than normal frame construction.
Recent users of this design include GT, Huffy and Nashbar.
High (gear)
- A high gear is one in which the pedals move slowly compared to the speed of the wheels. High gears are achieved by using large chainwheels and small rear sprockets.
High gears are for going fast, when the terrain permits. The rider must push much harder on the pedals in a high gear, so high gears are not suitable for lower-speed riding, due to the great strain that hard, slow pedaling puts on the joints.
High flange hubs
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- Before the use of chain drive, bicycles had direct drive. The cranks were directly attached to the hub of the drive wheel. The larger the wheel, the farther the bicycle would move with each turn of the pedals. The diameter of the drive wheel determined the gear of the bicycle. The larger the wheel, the higher the gear.
With a chain-drive bicycle, you can have any gear you want by selecting appropriate sprockets. With a high-wheel bicycle, the limiting factor is how long your legs are, because you can only pedal a wheel that is small enough for your legs to straddle and reach the pedals throughout the pedal revolution.
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Hook edge rims
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- The outer sleeve through which a brake or gear cable is pulled. The housing transmits an equal push to counter the pull on the inner cable. Traditional housing consists of a tight spiral of steel wire, usually coated with plastic. Newer versions have synthetic liners to reduce friction. This type of housing is still used for brake cables. See also Bowden cable.
With the advent of index shifting, greater precision was required, particularly for handlebar-mounted shift controls. For this application, "compressionless" housing is now used. This differs from traditional housing in that the wire part consists of a bundle of parallel wires, running more-or-less parallel to the cable. This reduces the tendency of the housing to change effective length when it flexes as the handlebars turn. This type of housing should not be used for brake cables, as it is likely to rupture under the higher loads involved in braking.
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- The middle part of a wheel, to which the inside ends of the spokes attach. Consists of an axle, which attaches to the fork ends; a shell, to which the spokes attach, and bearings to connect the axle to the shell, permitting the shell to revolve around the axle. In the case of a rear hub, the shell would also have a provision for attaching the rear sprocket(s). Some hubs incorporate a coaster, drum, disc or roller brake. Some rear hubs also incorporate internal planetary gearing.
Hub brake
- A brake that is incorporated into the hub of a wheel, as opposed to a rim brake.
Hub brakes activated by back-pedaling are called coaster brakes ("back-pedal brakes" in British usage.)
Hand-operated hub brakes include disc brakes, drum brakes, and
roller brakes.
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- A hybrid is a cross-breed, the result of taking features from two different sources and creating something different, with aspects of both.
- Hybrid bicycles*****
- Hybrid gearing*****
Hyperdrive-C ®
- Shimano's buzzword for compact drive.
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- A system of ramps and special-shaped teeth on Shimano rear sprockets that permits much smoother shifting than older systems. HG sprockets are designed so that, as the chain moves from one sprocket to the next, it will engage the new sprocket before it has completely derailed from the old one. This makes for smooth, silent shifting.
Hyperglide requires that the teeth of adjacent sprockets be oriented specifically with respect to one another. It also reduces interchangeability to some extent. For example, a 17 tooth sprocket that is designed to be used next to a 16 tooth sprocket will be shaped differently from on designed to be next to a 15 tooth.
More information on Hyperglide cassettes is available in a separate article on this site.
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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
IG ®
- Interactive Glide is an extension of Hyperglide, in which both sides of the sprockets are contoured to improve upshifting.
Indexed shifting
- Indexed shifting means that the shift control has positive detents or click stops that provide discreet positions corresponding to different gears. See friction shifting
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
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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 bicyles are built to specific standards of threading and dimension. Most parts on Italian dimension bicycles are interchangeable with British/I.S.O. 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/I.S.O. 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/I.S.O., except for the thread angle difference. They may be interchanged, but you should not go back-and-forth bewteen Italian and British/I.S.O. headsets. Italian freewheels are basically extinct, so the issue is moot there.
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- The International Standards Organization. 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.
In the case of tires and rims, the I.S.O. 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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Jam Nut
- A thin lock nut.
Japanese Industrial Standard (J.I.S.)
- 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.
Jumper
- African-American term for "derailer".
K-7
- 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
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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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- 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.
Klingon
- Wheel sucker. Term popular with tandemists, generally refers to solo cyclists who draft tandems.
Knobby
- 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.
Krate
- Schwinn trademark for a family of wheelie bikes. These have become quite valuable to collectors.
Lawyer lips, lawyer tabs
- 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."
Lightweight
- Traditional U.S. bicycle industry term for bicycles with tires narrower than about 1.5".
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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.
Lost Wax casting
- See investment casting.
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Low (gear)
- 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.
Lowrider
- 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.
LWB
- Long Wheel Base (recumbent)
