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Bicycle Glossary - T


Tandem (tan' dem) - A bicycle built for two or more riders. The front rider steers and controls the brakes and shifting. Sometimes but rarely, rear riders are also provided with brake handlevers. Almost all tandems are arranged with the riders in line, one behind the other. Side-by-side tandems have been created but are very rare. They are typically called 'sociable' bikes. The longest tandem ever built carried thirty-five riders.

Tension Pulley (pull' ee) - The lower of two pulleys on a rear derailleur. This one wraps the extra length of chain that exists when the selected gearing uses other than the largest sprockets. Most derailleurs have friction (sleeve) bearings in their pulleys which last longest if disassembled and greased now and then. Some have ball bearings. The tension pulley is more prone to corrosion and dirt because it is closer to the ground. Fortunately, it is also the easiest to overhaul. See also: Guide pulley.

Third hand tool - A tool that squeezes a brake caliper together so you can work on it without struggling against cable tension. This is most often used for pulling the slack out of the brake cable. Many bicycle professionals pride themselves in being able to work on brakes without using a third hand tool.

Three-piece crank - A cottered or cotterless crank set. See Cottered and Cotterless for details.

Three-speed - A system in which a planetary gear set (which see) in the rear wheel hub allows for differing gearing. 

Three-speed conversion - It is possible to combine a multiple-sprocket freewheel with a planetary gear set. This is called a "three-speed conversion." Your author took this about as far as can be done by making a ninety-speed bicycle. The bike had a five-speed planetary gear set, with a six-speed freewheel (five times six is thirty), and a triple chainwheel (thirty times three is ninety)! The bicycle had four shifters. The arrangement was not very practical, but it made a nice conversation piece.

Thumb shifter - A shifter mounted on the handlebar near the grip which you operate with your thumb. See also: Trigger shifter.

Tie-wrap - A tough flexible plastic strap typically eight inches long and a quarter-inch wide which has a tiny ratchet at one end. You can stick the tail end of a tie wrap into the ratcheted end, and pull it tight. The tie wrap cannot be undone, unless cut off. Tie wraps are used as cable ties to keep control cables from flapping or hanging, to fasten baskets to handle bars, to tie on racing number plaques, and numerous other purposes. Tie-wraps are not particularly pretty, but they are a nice, inexpensive utility device. 

TIG welding - (Tungsten Inert Gas) An arc welding technique in which the site of the welding is surrounded by a neutral gas that keeps oxygen and hydrogen away from the hot metal, preventing weakening that would otherwise occur due to rapid corrosion.  The heat for the welding is generated by a controlled electrical arc between the piece being welded, and a tungsten electrode. Metal rod is fed into the weld to build it up with more bulk (a bead is created). 

TIG welding requires more skill than MIG welding and therefore is not a common mass-manufacturing technique. See also Welding, MIG welding, Oxy-acetylene, Brazing and Silver Brazing.

Time trial - A competition, generally held on pavement, in which the riders are competing against the clock, and are released at intervals. There is no photo-finish. The winner is not known until the times are compared.

Tire - A soft device mounted on bicycle wheels that contacts the road giving a more efficient, comfortable and durable ride than if the metal wheels contacted the road directly. Most bicycle tires contain air under pressure to cushion the ride, and decrease rolling resistance. Air-filled tires are called 'pneumatic tires.' The tires are made from a cloth casing, covered with natural or artificial rubber. Most tires are black because carbon is added. Tires would wear out very quickly if not for carbon or other additives. Tires with gum sidewalls are more efficient than those with black sidewalls because less heat (friction) is generated in flexing and unflexing the sidewall as the tire rolls. However, gumwall tires do not last as long in the sun. 

Tire bead - Almost all tires except sew-ups have a metal, fiberglass, or plastic cable running along the edge of both sides called the "bead." This is molded into the tire so you can't see it. The purpose is to keep the tire from expanding due to the air pressure and blowing off the rim

Tire lever - A tool for removing tires from rims. Most tires can be removed without tools by deflating fully, and lifting a section of the tire over the edge of the rim. Once a section is over the rim, the rest slips off easily. However, some tires are just too tight, especially thin tires. For these, you need tire levers. Tire levers are flat metal (or plastic) plates which you insert between the tire and the rim to pry the tire over the edge of the rim. There are two or three levers in a set, because often you need to insert one tire lever, and while leaving it in position, insert another tire lever a few inches away to pry more of the tire over the rim. After awhile, enough of the tire is over the rim to remove it the rest of the way by hand. Tire levers have hooks in their back end so that they can be hooked onto a spoke, leaving the hands free to insert a second or third tire lever.

Tire Liner - A strip of rubber or plastic material that goes around the rim, inside the tube to protect it from the rim. Poor tire liners that sometimes come with new bikes need to be replaced immediately when purchasing even a high quality bike.


Titanium - A soft, gummy metal, with a dark gray, almost greenish tint, which if used correctly can make very strong bicycle frames and components in comparison to its weight.

Toeclips - Springy brackets attached to the fronts of pedals that keep your feet in position. The toeclips extend over the top of your toes and are used with toestraps which wrap around the pedals and the front of your shoes. With this arrangement, you spend less energy in keeping your feet in position. Normally, quite a bit of efficiency is wasted, due to the need to keep your feet on the pedals. And, you can pull up on the pedals, using an additional set of muscles which are not otherwise well implemented.

Unless you use cleated cycling shoes, you can get out of toeclips very quickly by just slipping your foot backward off the pedal. Commuters who use toeclips become so used to them, that they never think about stopping. They just put a foot down when they need to stop, like everyone else. The backward motion to exit the toeclip becomes automatic.

To get your feet into toeclips, you tick the edge of the pedal with your toe, which causes it to rotate up to meet your foot, as you slide your foot forward, and securely into the clip. Very easy with just a bit of practice. 

Toe clips are made from chrome-plated spring steel, or strong flexible plastic.

Toe-in - Because brake pads that are exactly parallel to the rim may squeak when applied, mechanics may toe them in slightly. This means the brake pads are set so that only the trailing edges touch the rim if the brake is applied lightly. If more pressure is applied, the whole pad comes in contact with the rim. This is called toe-in. On most cantilever brakes, and some other caliper brakes, adjustment for toe-in is provided. On some sidepull and centerpull brakes, the caliper arms are bent to accomplish toe-in. Do not bend brakes unless you are sure the brakes in question can take it. For instance, most Italian centerpulls cannot be bent without risk of cracking, and trying to bend some cantilever brakes may tear the brake post off the frame

Toe straps - These are leather or nylon straps which are used with toeclips. They have buckle which allows for pulling on the end of the strap, which sticks out a couple of inches, to tighten yourself in. You can just press a finger on the buckle to instantly loosen the strap.

Tongue and Groove Pliers - Frequently called "Channellocks" this type of plier can be opened to differing amounts. It is a crude tool, which is best ignored in favor of something more appropriate whenever possible. The jaws of this pair of pliers is likely to leave marks on the metal parts of your bicycle. However, there are places where these work well. If you don't care about the appearance of your work, they are a quick and dirty tool for turning nuts and bolts. Tongue and groove pliers can grip shafts and tubes, and can be opened wider than other tools except for large wrenches. This tool is also used for bending metal.

Toptube - On men's, or diamond frames, and on mixte frames, this is the frame tube which extends from the headtube (through which the fork is mounted) to the seattube. Most toptubes are one inch in outside diameter. On French bikes, the toptube is 24 millimeters in diameter.

Torque - Rotational force. The most common torque measurement is foot-pounds, equivalent to a weight in pounds being set on the end of a wrench that is one foot long.

Torque wrench - A tool that accepts sockets to fit nuts and bolts, and which allows you to guage how much you tighten those nuts and bolts. Torque wrenches have either a gauge showing the torque being applied, or they click audibly when a preset torque is reached.

Torx - A style of screw and matching six-sided screwdriver that is like Allen bolts, but the tools to turn these screws are not interchangeable with Allen bolts. Torx are somewhat more star-shaped than Allen bolts and come in sizes numbered 5, 10, 15 and 20.  These are not yet common in bicycle parts but since they have been popular in other machinery, they may show up in bicycle technology soon.

Touring - Recreational bicycle riding in which the rides are more than one day in length. Touring can be done with complete camping gear, or by spending the nights at hotels or friends' houses. See also: Day trip.

Track - A racing facility which is a large oval. The original tracks were housed in buildings, and made from smooth wooden boards, and were banked such that the outside edge of the track was higher than the inside edge. Many track events today are held outdoors on pavement, because bicycle tracks are not common. Track also refers to a race of the type held in tracks, which include time trials pursuits and sprints.
Synonym (for a building housing a track): Velodrome.

Track bike - A specialized racing bicycle with fixed gearing (the sprocket at the rear wheel is solidly attached so you cannot coast), low handlebars, no brakes, and thin, very high pressure tires. These sacrifices are made to reduce the weight of a track bike to the bare minimum. Track bikes even have fewer spokes than road bikes. Most road bicycles have 36 spokes per wheel. Track bikes have from 24 to 36 spokes per wheel, with 32 being the common number. Track bikes use silk sew-up tires.

Because there are no brakes and the rider's feet are cleated securely to the pedals, track bike riders have developed some special techniques. One, the track stand (which see) allows the rider to maintain balance with both feet on the pedals even though the bicycle is completely stopped. There are at least two ways to stop besides slowing down gradually. One is to rub a foot on the front tire. This is seldom seen, because you need to remove a foot from a pedal first, and that's difficult since you can't coast on a track bike. Trying to release the toe strap is like trying to hit a moving target. The other way to stop is quite interesting. The track racer leans forward and pops the rear wheel off the boards (racing tracks are traditionally made of wood). The rider then stops pedaling and offers resistance to the pedals. When the bike comes down, the wheel is already stopped, and so it skids. This too, is seldom seen, because track tires are too thin to take much skidding. 

Track stand - A technique of balancing in which the rider can come to a complete stop without removing any feet from the pedals. This was originally used by track riders in pursuit races in which they might come to a complete stop while waiting for the other rider to try to take off first. That would be a disadvantage because the other rider can then draft the leader and take advantage of less wind resistance. Now, track stands are used by any riders with toe clips who like to keep their straps tight, yet may have to stop for traffic, and by anyone who wants to play with a fun trick! 

To learn the track stand, start on a quiet, smooth paved surface which is not quite level. Aim either the bicycle or the front wheel uphill. The front wheel should be turned nearly ninety degrees to the direction the bicycle is facing. By pushing slightly on one pedal, the bike will roll a couple of inches uphill. Let it roll back. Continue this rocking motion, and soon you will start to feel the possibility of balancing. With practice, it is natural and quite stable. Experts can do track stands with one hand, and a few can even do it with no hands. For no hands, it helps to press one leg against the toptube of the bike. 

Experts can also do it on level surfaces using any of three variations of the technique. One is just being good at balancing, and knowing that no surface is totally level. The second is to use the front brake to stop the forward aspect of the roll. By applying the front brake hard, the bicycle will actually spring backward a bit, so you can maintain the rocking motion. The third technique is to place one foot on the back of the front tire, and actually push the tire to roll backward and forward. Synonym: Invisible kickstand.

Trailer - A device with one or more wheels that follows a bicycle to carry cargo or children. If you build your own trailers consider that for best performance, they should have a very low center of gravity. The wheels (if you use two or more of them) should be wide apart to prevent tipping over, yet the whole trailer should be narrow to operate comfortably in traffic, and the trailer should be strong yet light weight. The hitch between the bicycle and the trailer should be flexible in all directions.

Trigger shifter - A shifter mounted on the handlebar near the grip which you operate with your thumb. Synonym: Thumb shifter.

Triple-century - A ride covering three hundred miles in one day, not a common feat! See also: Century, Double-century.

True - A situation in which a wheel or other rotating device such as a chainwheel is in proper lateral alignment.

Truing - To bring a wheel or other rotating device, such as a chainwheel into proper alignment and remove eccentricity. 

Truing stand - A bench-mounted device to hold bicycle wheels while they are being aligned ("trued"). The truing stand has one or more indicators that can be adjusted close to the wheel's rim.  As the mechanic slowly turns the wheel back and forth, bent places are easy to see because they come close to, or touch the indicators.  

Some truing stands have dial indicators.  A dial indicator is a round gauge that has a feeler that touches the rim and shows more clearly even very small variations in alignment.  

Some also have precise, adjustable alignment between the portion that holds the wheel and the portion that holds the indicators so that wheels can be adjusted for proper dish in the truing stand.  Proper dish means that the rim is centered over the hub.  This is not usually an issue with front wheels, but many rear wheels have to be 'dished' to accommodate the freewheel.  The freewheel takes up some room on the right side of the hub, so the hub flanges are offset to the left. Therefore, the spokes on the right side have to be shortened somewhat, so that the rim is centered over the whole hub, not the hub flanges.

A truing stand is not required for good and complete bike repair, it just makes it faster.  If you don't have a truing stand, you can reinstall the wheel on the bike, and use the brake pads as indicators.

Tube - Synonym for "Inner tube" - which see.

Tubing - Synonym for "Frame tubing" - which see.

Tubular - A thin, high-pressure tire which is tubular in nature, like a donut. Tubulars are generally used for road racing and by tourists who want maximum efficiency and lowest weight. The tire can be inflated without being mounted on a rim because the inner tube is sewn into the tire, much like an American-style football. Synonym: Sew-up. See Sew-up for more details.

Tune-up - A series of adjustments and sometimes minor repairs and cleaning which are sold as a package and bring a bicycle back into safe and efficient condition. 

How-to: Tune-up a bicycle- step by step

Twistgrip - A type of shifter combined with a handgrip. You change gears by turning the grip. 


Anything missing or need greater coverage? Let me know - Jeff

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Although I have attempted to cover the major safety issues, I cannot be responsible for your use of this information. Working on bicycles is dangerous if you do it without considering consequences of bolts left loose, known problems which are ignored, things which should be replaced but are glued instead, and so on. Proceed carefully at your own risk and use common sense. Jeff Napier, and all agents associated with this information, do not offer any guarantee or warranty for your use of this information.


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