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
B-Tension Adjustment
- Shimano terminology for the screw that regulates the tension of the upper-pivot spring of a rear derailer. It should be adjusted with the bicycle in its lowest gear. Loosening this screw allows the jockey pulley to swing up closer to the cluster, improving shifting.
If the B-tension is too loose, however, the jockey pulley will bump into the largest rear sprocket, causing noisy running and possible shifting problems.
See my article on Derailer Adjustment for more information on this and other derailer adjustments.
Back-pedal brake
- British term for coaster brake.
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- A ball bearing is a type of bearing in which the turning part is connected to the non-turning part only by balls that roll between the two parts. Ball bearings are used in bicycle bottom brackets, freewheels, headsets, andhubs. They are also occasionally used in derailer pulleys
and brake calipers.
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- A wide, low-pressure tire, typically 2.125" (54 mm) wide. The development of balloon tires and "streamlined", curved-tube frames created a mini bike boom in the 1940's. These bikes are pretty much indistinguishable from modern cruisers, and were the ancestors of the mountain bike, which was built around the popular sized balloon tires.
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- A type of seat popular on wheelie bikes, which extended well back from the seat post. The rear end of the seat was supported by an upside-down "u" shaped brace called a "sissy bar" which attached to the rear axle or to the rear fork ends. Some banana seats had spring suspensions built into the sissy bars.
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- Handlebar extensions which mount on the ends of a straight-ish mountain-bike style handlebar to provide extra hand positions.
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- Sun Tour trademark for derailer shift levers which mount in the ends of (usually) drop handlebars, replacing the normal end plugs. More formally known as "handlebar-end shifters" or "bar-end shifters," but not simply as "bar ends."
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- A form of "helper spring" for rear derailers. This is a fitting which slips over the rear derailer cable just in front of where it disappears into the final loop of housing that leads to the derailer. It includes a length of rubber tubing. The cable runs down the middle of this tubing, and a setscrew clamps one end of the tubing to the cable. This serves two purposes:
- It completely seals this vulnerable entry point against schmutz thrown up by the front tire.
- The rubber tubing acts as a "helper spring" to retract the cable smartly when upshifting. This can provide better upshifting on any bike that has a problem in that area due to excessive friction or a derailer with a weak spring.
****** B.C.D.
- Bolt Circle Diameter
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- A hoop, usually of heavy steel cable, that forms one edge of a tire. Sometimes made of Kevlar ®; for lightness and foldability.
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- A bearing is the point of contact between a turning part and a non-turning part. A good bearing assembly has little or no play, and as little friction as possible.
Major bearings on a bicycle are the headset, the bottom bracket and the hubs. There are also bearings in brakes, pedals and freewheels.
Bearings used in bicycles are usually of the cup-and-cone type, but many newer bicycles use cartridge bearings.
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- A steel ball that is part of a ball bearing assembly. Most front hubs use 10 3/16" balls on each side; Most rear hubs use 9 1/4" balls on each side. Most bottom brackets use 11 1/4" balls on each side.
Bearing balls are made in batches, and within a batch the size is very carefully controlled. From one batch to another, however, there can be a considerable variation in actual size of balls of the same nominal size. For this reason, balls from different batches should never be mixed in the same bearing.
Bearing balls come in several quality grades, designated by numbers. Grade 25 is the best that is available for bicycle applications. Grades 100, 200, even 300 are commonly used in bicycles.
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- A defunct British maker of derailers.*****
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- Recumbent bicycle or tricycle.
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- French term for a water bottle.
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- Noun: bicycle; motorcycle. Many cyclists object to verb-based derivatives of "bike" i.e. "to bike", "biking", "biker"...(Bikers ride Harleys, people who ride bicycles are cyclists.)
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- In the early-to-mid 1970's, bicycling as an activity for adults suddenly became wildly popular, after several decades when the bicycle was commonly regarded as a child's toy.
The Bike Boom was partly related to the Baby Boom, as Boomers were starting to enter adulthood in large numbers. Other factors were the popularization of 10-speed derailer-equipped bicycles, and the oil crisis of 1974.
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- A solid chunk of metal, usually in the form of a slab or a piece of cylindrical stock. Commonly cut into usable parts by CNC machinery.
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- Another name for a pinch bolt, usually used to refer to the seat-post bolt.
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- A type of non-round chainwheel introduced by Shimano in the 1980's. It is designed to provide a more natural motion of the foot, better off-road traction, and to reduce stress on the knee. See my article on Biopace for more details.
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- Most tires use rubber blended with carbon black, because carbon black makes the tread more durable and improves traction.
In the 1950's, some tire companies started using "gum" rubber (without the carbon black) for the sidewalls, in the interest of improved flexibility and lowered rolling resistance.
Later, "skinwall" tires became popular, tires with nearly naked cloth sidewalls, with just a bit of rubber to hold the cords together. For many years, tan sidewalls, whether gum or skin, were a sign of high-performance tires, and blackwalls were a sign of cheapness.
In the early 1990s there was a styling fad for tires which were basically skinwalls, but looked like the old black-walls. Although the marketing departments of the tire companies involved tried to make this out as some kind of advantage, it is fundamentally a styling issue, as with white walls.
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- One of the two "tines" of a front fork.
- A spoke that has been flattened in the direction of rotation for improved ærodynamics. "Bladed" spokes are so wide that they will not fit through the spoke holes of a standard hub flange. The usual solution to this problem is to file a notch or two to enlarge each spoke hole. This is very labor-intensive, and risks creating a stress riser which can lead to flange failure.
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- Short for freewheel block; cluster.
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An obsolete type of chain, formerly popular with track racers.
Block chain had solid blocks as inner links, without rollers. It had
a 1" pitch with 3/16" wide blocks, the same as the
"skip link" roller chain that appeared on the market about 1930
to replace it.
The remaining stock of block chain was coveted
by track riders who believed it was the only chain strong enough
to withstand their imagined strength. When the stock of block
chains finally ran out in the late 1970's, it was replaced by
1/2" pitch 3/32" wide chain, as used with derailers, although track riders still
prefer an 1/8" wide chain, believing they are stronger than
other riders. MTB's with 18 tooth granny chainwheels produce several
times the chain tension any track rider can muster.
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- Bicycle Motocross, a type of dirt-track racing, primarily for children. Competitors usually ride 20" wheel, single speed bicycles with a freewheel and a rear hand brake. Races, called "motos" usually last less than two minutes, and feature jumps. High level BMX races mostly hinge on getting a good start off the line, which, for some reason, is called a "hole shot" BMX tracks use mechanical starting gates that fall forward under the riders' wheels when released.
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- On a crank set, the diameter of the circle formed by the stack bolts.
Standard double chainwheel sets use 130 mm or 110 mm diameters.
Modern triple chainwheel sets have two diameters, a large one for the two outer chainrings, and a smaller diameter, with a separate set of bolts, for the granny ring.
Full-size triples usually use 110 mm/74 mm, though some that are made for road use use 130 mm/74 mm. Campagnolo uses 135 mm/74 mm. Compact triples commonly use 94 mm/58 mm.
Some 5-bolt crank sizes:
"C-C" is the distance between adjacent stack bolts.
This is easier to measure directly than the actual Bolt Circle Diameter.
BCD
(mm) | Smallest
Ring | C-C
(mm) | Application
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| 151 | 44 | 88.8 | Very old Campagnolo standard (pre '67) (Obsolete)
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| 144 | 41 | 84.6 | Old Campagnolo standard, still used for track applications.
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| 135 | 39 | 79.5 | Current Campagnolo standard
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| 130 | 38 | 76.4 | Standard Road double
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| 128 | 38 | 75.2 | Nervar (Obsolete)
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| 122 | 38 | 71.7 | Stronglight 93, others (Obsolete)
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| 118 | 36 | 69.4 | Ofmega, SR (Obsolete)
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| 116 | 35 | 68.2 | Old Campagnolo (Obsolete)
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| 110 | 34 | 64.7 | Touring double, standard triple outer
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| 94 | 30 | 55.4 | Compact triple outer
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| 86 | 28 | 50.5 | Stronglight 99, some SR triples. (Obsolete)
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| 58 | 20 | 34.3 | Compact granny
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| 56 | 20 | 32.9 | Sun Tour Compact granny (Obsolete)
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- A television set. (Boob: "A stupid or foolish person; a dolt" (who watches too much TV); Tube: the cathode ray tube of a TV receiver.)
Some misguided souls use this term to describe the keel tube of a tandem frame. This makes no sense semantically. It probably arose because somebody couldn't think of one of the several more descriptive terms, and picked somthing cute sounding out of the air. It is to be hoped that this foolish term will disappear into the dustbin of history.
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- Keel tube. Also, the tube (often adjustable by telescoping) that holds the "bottom bracket" on a short-wheelbase recumbent.
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- The bosses of cantilever brakes can flex outward when the brake is applied hard. This contributes to a "spongy" feeling to the brake lever, and, in some cases, the extra flex may permit the brake lever to bottom out against the handlebar.
A "brake booster" is a metal bridge that connects the outer ends of the two cantilever bosses, holding them in position and greatly reducing their tendency to flex under load. A booster resembles an inverted "U", as it curves up and over the tire.
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- Slang term for a non-quick release hub or axle. More properly, these should be referred to as "nutted" or "solid axle" units, since conventional hubs use nuts, not bolts.
A very few high-end hubs actually do use bolts, usually with an Allen head. Among these are American Classic, Bullseye, and Phil Wood.
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- The earliest type of bicycle, from the mid 19th century. A boneshaker had wheels of roughly equal size, like a modern "safety" bicycle, but the pedals were directly connected to the front hub, as with a high wheeler.
Boneshakers existed before the invention of Dunlop's pneumatic tire, and had wood or iron wheels, with iron or (later) solid rubber tires. This caused them to provide a very harsh ride, hence the name.
The bone shaker evolved over time into the high wheeler, with the drive wheel getting larger and larger, the rear wheel shrinking down.
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- A bump or protrusion. This term has several specific bicycle usages:
- Cantilever bosses are the brazed-on pivots for cantilever brakes.
- Shift lever bosses are brazed-on pivots for down-tube-mounted shift levers. Most newer "road" bicycles have the shifters mounted on the handlebars, so they use the old-style lever bosses as attachment points for housing stops
- Older style freewheel pullers had two (or four) protruding bosses that engaged the notches of the freewheel body. This system was prone to failure when removing freewheels that were unusually tight. The development of splined freewheel removal systems made this obsolete
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- The part of the frame around which the pedal cranks revolve, also the bearings and axle assembly that runs through the bottom bracket shell of the frame.
| A conventional cup-and-cone bottom bracket. The lock ring wrench is about to loosen the lockring, the pin wrench is engaging two of the holes in the adjustable cup |
| A cartridge bottom bracket. The splined tool is shown above the bottom bracket. The crank would need to be removed to actually use the tool.
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An old American term for "bottom bracket" is "hanger". This is usually used in connection with one-piece cranks.
Bottom brackets come in different sizes, according to the nationality of the frame.
| Standard: | Threading | Adjustable
(left) cup
direction | Fixed
(right) cup
direction | Shell
Width
British
I.S.O. | 1.370" X 24 tpi
1.375" X 24 tpi | right | left | Standard 68 mm
O.S. 73 mm | The overwhelming majority of bicycles in current production.
British and I.S.O. are interchangeable.
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| Italian | 36 mm X 24 tpi | right | right
(wrong!) | 70 mm | Italian and some high-end French bicycles.
Prone to problems due to the right threaded fixed cup, which tends to unscrew itself in use.
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| French | 35 mm X 1mm tpi | right | right
(wrong!) | 68 mm | Obsolete, used on older French bicycles.
Prone to problems due to the right threaded fixed cup, which tends to unscrew itself in use.
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|---|
| Swiss | 35 mm X 1mm tpi | right | left | 68 mm | Same thread as French, but fixed cup is left threaded for reliability.
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| Raleigh | 1 3/8" X 26 tpi | right | left | 71mm
76 mm | Older British-made Raleighs, especially 3 speeds.
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O.P.C.
Ashtabula | Male threads
on crank
24 tpi (most)
28 tpi
Schwinn,
Mongoose | | |
68 mm (2.68") wide
51.3 mm (2.02") i.d.
(approximate) | Older U.S. bikes, BMX, Juvenile bikes, Department store bikes.
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- See Top pull.
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- The type of concentric cables used for brakes and gears was once known by the term "Bowden cables", after their inventor.
There was a famous legal case arising from Bowden's cables. He licensed many manufacturers to manucfacture cables based on his patent, but failed to exercise quality control over the licensed products that bore his name. As a result, the patent and trademark were deemed to have been abandoned, and became public domain. (I am not a lawyer, I heard this from a lawyer some time ago, I don't vouch for the accuracy of the legal information...)
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- The short length of tubing connecting the seatstays just above the tire. This is the usual mounting point for a rear caliper brake.
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- An alloy of copper and zinc, in the proportion of about two parts of
copper to one part zinc. The zinc makes brass stronger and harder than copper is alone. It is easy to work, and doesn't rust. Most spoke nipples are made of brass, because it is easy to thread and will not rust to the spoke threads.
Brass is also easy to cast, and has been used for derailer parts and quick-release skewer acorn nuts, and for thrust washers in caliper brakes.
Various special brass alloys are used as filler material for brazing.
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- A small fitting permanently attached to a frame. On traditional steel frames these attachments are held on by brazing, but the term "braze-on" is also used for fittings that are welded, glued, rivetted or moulded on to frames of other materials. Typical braze-ons would include cable stops and guides, water bottle cage mounts, shift lever bosses, cantilever brake bosses and cable stops, pump pegs, etc.
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- Brazing is the joining of metal parts by melting a different metal (of lower melting point) which bonds the parts together. Typically brazing involves joining steel parts with molten brass. Soldering is a similar operation, using lower temperatures and different filler metals (with a lower melting point) In brazing and soldering, the filler metal penetrates inaccessible areas of the joint by capillary action.
See also welding, fillet brazing.
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- ***** wrench
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- A randonnée to qualify a rider to enter a longer randonnée.
This is a French word, variously translatable as "diploma," "certificate" or "patent."
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- *****
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- In the early days of bicycle manufacture, every industrialized country had its own system of thread sizes and standard dimensions for bicycle parts. The British system is the one that has, by-and-large, prevailed. British dimensions have mostly been adopted by the I.S.O. These standards include 1" x 24 tpi headset threading, 1.375" x 24 tpi bottom bracket threading (left-hand on the fixed cup). This is not to be confused with Raleigh dimensions.
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- A maneuver consiting of locking the rear brake while turning, so that the rear wheel oversteers and the bike comes to a stop in a cloud of dust, while turning up to 180 degrees. Usually performed with the inboard foot off the pedal and extended inward to act as an outrigger.
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- The world's foremost maker of leather saddles. Brooks is based in England, and is one of the oldest companies in the bicycle industry. They were formerly also the leading maker of English-style touring bags.
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- Balanced Response System. Dia Compe's system of adding a weak return spring to the brake lever. Since the cable was being pushed at one end and pulled at the other, a positive return function could be attained with a much lower overall spring tension. This greatly improved the "feel" and sensitivity of the brake.
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- B.S.A. (Birmingham Small Arms) was a major British manufacturer of firearms, and later of bicycles and motorcycles. They reached their peak in the 1920's. The standard thread sizes that they developed for their bicycles were ultimately adopted as the standard British (B.S.C.) sizes, which, in turn, were mostly adopted by the I.S.O.
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- British Standard Cycle. The standard dimensions pioneered by B.S.A. were ultimately adopted by the bulk of the British cycle industry under this designation.
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- See "Cow Horn."
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- A style of handlebar popular on early mountain bikes. The handlebar and stem are a single unit, with the stem splitting in two at the quill and attaching to the handlebar at two points, forming a triangle.
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- An elastic shock cord with hooks on the end, commonly used for securing baggage to a luggage carrier. Also known as a "Sandow".
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- A manufacturing co-op, based in Eugene, Oregon. Burley is a leading manufacturer of tandems, trailers and rain gear.
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- Thicker at the ends. Said of spokes and frame tubing. (Butted spokes are also called "swaged") Butted tubing is usually made with a constant outside diameter, but thicker walls at the ends. The idea is to make the part stronger at the ends, where the stresses are greatest, and lighter in the long middle section, where stresses are less.
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