Sheldon Brown's Bicycle Glossary Ta (original) (raw)

Opinions and value judgments are our own, unless otherwise noted

-- Sheldon (d. 2008), Harriet, John.
Additions and corrections are most welcome.

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T.A.

Highly regarded French maker of bicycle parts. Best known for crank sets. T.A. was the pioneer in triple-chainwheel crank sets. T.A. also makes bottle cages and special orthopedic pedals for cyclists with legs of different lengths.

Taco

To collapse a wheel so that it assumes a saddle shape. A tacoed wheel is more than just out of true, it has collapsed so the spokes have assumed a new equilibrium position and lost tension. Two spots, 180 degrees apart will be way off to the left; two other spots, halfway between, will be way off to the right. A taco wheel is also known as a "potato chip" wheel, depending on the local food culture. Often, the rim is only flexed, not bent, and the wheel can be sprung back nearly to its original shape.

Tadpole

A tricycle with two wheels in front, one behind.

Tandem

A bicycle or other vehicle which accommodates two or more riders, one in front of the other. Tandems for three riders are called "triplets", for four: "quadruplets" or "quads", etc.

This site contains several different articles about tandem bicycles.

Tange

Noted manufacturer of frame tubing and headsets.

Tap

A tap is a tool for cutting internal threads. It takes the form of a bolt with flutes cut in the threads, and usually has a taper at the end that is intended to start the thread. There are only a few standard sizes used on bicycles:

The corresponding nut-like tool for cutting external threads is called a die.

My Tool Tips series features an article on the use of taps.

Major Taylor

50 years before Jackie Robinson joined the Brooklyn Dodgers, when bicycle racing was the most popular sport in the world, Marshall "Major" Taylor competed at the highest level, setting numerous world records and winning a world championship in 1899 -- with quiet dignity and in the face of extreme hostility and prejudice, even threats against his life. His example lends a higher meaning to the expression "sports hero". There is a fiction-based-on-fact story about him on this site. You may read more about him on the Web site of the Major Taylor Association.

Technomic ®

A series of handlebar stems made by Nitto. Technomic stems are very high-quality aluminum stems, in the traditional "7" shape popular for road bicycles. The special feature of the Technomic stem is that the vertical part of the stem is taller than usual. This is a great aid for fitting bicycles to riders who need a higher handlebar position than would otherwise be possible with a particular frame.

Tensiometer

An instrument for measuring spoke tension. See my article on wheelbuilding...

Tension Pulley

The lower pulley on a rear derailer. So called because its main function is to adjust the tension on the chain as different-sized sprockets are selected.

Terry ®

A line of bicycles designed specifically to meet the fitting needs of smaller women. Terry also makes and sells women's bicycle clothing, and saddles for men as well as women.

3rd hand

A clamping tool to hold the brake shoes tight against the rim, to make brake cable adjustments easier.

Threaded Driver

Older Sturmey-Archer hubs used threaded sprockets, similar to track sprockets, which screwed onto a threaded driver. Sometime in the 1940's, three-splined sprockets and drivers were introduced, which made it much easier to interchange sprockets.

To remove the sprocket from a threaded driver, the driver must be removed from the hub (otherwise it will just freewheel as you turn it counterclockwise.) As shown in the photo, one good way to secure it is to set it so that the legs are straddling a suitable steel bar, held in a vise. I use a pair of headset wrenches side-by-side, then unscrew the sprocket with a chain whip.

Threaded drivers are fairly rare, and are often sought after because they have the same thread as a standard freewheel hub. This makes it possible to create a hybrid gearing system by screwing a normal freewheel onto the driver. More details on this may be found in my article on my O.T.B. 63-speed bicycle.

Threaded Headset

Traditional style headset whose upper race and locknut screw onto a threaded fork steerer.

Threading Systems

For normal, generic nuts and bolts, there are two threading systems in common use, S.A.E. (U.S.Standard) and Metric (I.S.O.). S.A.E. threads are designated by a diameter and a number of threads per inch (TPI). For example, the common 1/4 - 20 means a bolt 1/4 inch in diameter, with 20 threads per inch. Metric bolts are sized by the diameter and the distance between adjacent threads, for example 6 x 1 refers to a bolt 6 mm in diameter with threads 1 mm apart. (This is the size used for brake mounting bolts and brake shoe hardware.) Similarly, 5 x .8 means a bolt 5 mm in diameter, with threads .8 mm apart. (This size is used for fender and bottle-cage fittings, shift lever bosses, and most cable anchor bolts.) A third system, known as Whitworth, was used in Britain up until the 1960's when the U.K. converted to metric.

Bicycle parts come in even more different thread systems than common nuts and bolts. There are different standards for headsets and bottom brackets for American/BMX/OPC, British, French, Italian, Raleigh and Swiss bicycles.

The table below is for threaded bottom-brackets. For the Ashtabula OPC and other unthreaded bottom brackets, see the unthreaded bottom-bracket cribsheet.

Bottom Bracket Threading

What happens if you try to mix different sizes:

Freewheel Threading

French and Metric BMX freewheels thread don't work with anything else.

ISO, English and Italian are all semi-interchangeable, but it you shouldn't go back and forth between different types of freewheels on the same hub repeatedly.

Headset Threading

Metric threads are specified by diameter followed by the thread pitch (distance between threads)

For example, the common "M5" thread used for water bottle mounts, cable anchor bolts, fender/rack eyelets, shifter mounts etc. bicycles is more specifically described as "5.0 x 0.8" which specifies a 5 mm diameter, with threads 0.8 mm apart.

Similarly, the common "M6" thread used for brake mounting bolts, threadless stems, many seatpost bolts and so forth is actually "M6.0 x 1.0" That's 6 mm diameter, threads 1 mm apart.

Normal coarse metric threads are commonly designated with the letter "M" followed by the diameter, with the thread pitch understood. For example:

• M2 = 2.0 x 0.40 mm
• M2.5 = 2.5 x 0.45 mm
• M3 = 3.0 x 0.50 mm
• M3.5 = 3.5 x 0.60 mm
• M4 = 4.0 x 0.70 mm
• M5 = 5.0 x 0.80 mm
• M6 = 6.0 x 1.00 mm
• M8 = 8.0 x 1.25 mm
• M10 = 10.0 x 1.5 mm
• M12 = 12.0 x 1.75 mm
• M14 = 14.0 x 2.00 mm To give another example, the common size derailer hangers and chainring stack bolts and is 10 x 1.0 mm. This is a fine thread, not a standard coarse thread, so it would be incorrect to refer to this simply as "M10" since the standard pitch for M10 is 1.5 mm.

Threadless Headsets

Headsets, such as the Dia Compe "Aheadset" ® which fit a smooth sided (threadless) fork steerer.

See the Headset entry for details and adjustment instructions.

Three-piece Cranks

Most bicycle crank sets are of the three-piece type, the three pieces being the left crank, the axle, and the right crank with chainwheel(s). Three-piece cranksets use either cotters or a tapered cotterless attachment. There are also two-piece crank sets and one-piece crank sets.

Thumb Shifter

The original style of shifter used on mountain bikes, up until the early '90s.

When the Shimano Rapidfire ® and Sun Tour X-Press ® shifters hit the market, confusion resulted, because these, too were operated by the thumbs. This confusion persists, so it is a good idea to avoid the term "thumb shifter." The newer term for these is "top-mount" shifters, as opposed to "below-the-bar" shifters, such as Rapidfire.

Tiller Effect

On bicycles where the handlebars extend well back from the steering axis, such as many cruisers and especially direct-steering long wheelbase recumbents, turning the handlebars also causes both grips to move noticeably to the side. In steering bicycles that suffer from tiller effect, you need to move your hands sideways to the side opposite which you're steering. Tiller effect can thus limit how tightly you can corner, as your arm length may limit the amount by which you can turn the handlebars. On an upright bicycle where some of the rider's weight rests on the handlebar, tiller steering makes it awkward to ride with only one hand on the handlebar, because of the tendency of the weight to push that end of the handlebar forward.

T.I.G. Welding

Tungsten Inert Gas welding. A form of welding by the use of an electric arc. The area being heated is bathed in an inert gas to prevent oxidation.

T.I.G. welding is commonly used to build lugless bicycle frames. Most current bicycle frame production is done by T.I.G. welding.

Timing Chain

see Sync chain.

Time Trial

A race in which competitors start one-at-a-time, usually at 30-second or one-minute intervals. The winner is the cyclist who completes the course in the shortest time. Since drafting is not allowed in an individual time trial, there are no team tactics; it is just the cyclist against the clock, hence the sobriquet "the race of truth."

The cycling leg of a triathlon is a form of time trial.

There are also team time trials, usually involving teams of 4 or more, taking turns leading and drafting each other. Team time trials require great precision in rotating position within the team.

Time trials are held both on the road and on the track. Bicycles made for time-trial use are designed to be as aerodynamic as possible, even at the expense of degrading handling characteristics and rider comfort. Since riders are on their own, there is no need for fancy maneuvering as there is in a peloton.

Tire

People usually think that tires are made of rubber. This is understandable, because rubber is all that you can see.

A tire is actually made up of three parts:

1. The beads are two hoops of strong steel wire (or, sometimes Kevlar ®.)
2. The cords are cloth, forming the body of the tire, woven between the two beads. Most modern tires use nylon cords.
3. The rubber covers all the other parts. The rubber on the part that contacts the road is thicker, and is called the tread. A bicycle tire is not airtight by itself, so it uses an inner tube, which is basically a doughnut-shaped rubber balloon. The inner tube has a valve to allow you to blow it up. (Some newer tires are tubeless, like car tires, but tubeless tires are not very common as of yet. There is a complication in that the tire beads are much narrower than with car tires, so it is harder to form a seal. Time will tell.

This site includes an extensive article on Tires and also an article explaining the different Tire Sizing systems.

Tire Lever, Tire Iron

A special tool for prying the bead of a tire over the rim. Most tire levers have a rounded end which slips between the rim wall and the tire. The other end of the lever is bent and has a notch. Once you have inserted the first tire lever and pried one section of the bead over the edge of the rim, you can hook the other end around a spoke. This leaves your hands free to stick another lever in, usually two spokes over from the first.

One or two tire levers are usually enough to get all but the most recalcitrant tire beads over the rim, but in extreme cases you may need three. When the third is in place, the middle one can be removed and re-inserted farther over. Tire levers are usually sold in sets of three, since you never need more than three.

Since most newer tire levers are made of plastic, the term "tire iron" is a bit anachronistic.

Tire Saver

A frame/fork-mounted device designed to brush sharp debris from the tread of tires before it can penetrate through to the inner tube. Tire savers usually attach to the brake center bolt, and are commonly made from recycled spokes.

Titanium

One of the better materials for making bicycle frames. It is very strong, rustproof, and light.

See my Article on Frame Materials.

Titanium Nitride (TiN)

Titanium Nitride is a very hard ceramic surface treatment used on metal parts to reduce friction and extend wear life.

See Wikipedia for details on this.

Toe Clips

Toe Clips are stirrup-like devices that attach to pedals. They are normally used with leather or fabric straps. Actually, the straps are more important than the clips, but without the clips it is nearly impossible to get into the straps, because the clips hold the straps open, allowing the rider to slip into them.

Toe Clip Overlap

On many bicycles, especially those with smaller frames and full-sized wheels, it is possible for the front fender or tire to bump into the rider's toe or to the toe clip. Some people worry a lot about this, but it is rarely a significant problem in practice.

The only time it can happen is when the handlebars are turned quite far to the side, as only happens at very low speeds.

Many, many people ride bicycles with fairly severe overlap with no practical problems, sometimes having to make a slight adjustment to their pedaling habits at very slow speeds.

On smaller-size bikes with full-sized wheels, it is usually impossible to eliminate overlap without causing adverse fit/handling issues.

Toe-In

When a brake shoe presses against a moving rim, the pull of the rim causes the brake arm to flex a bit. If your brake shoes hit a stationary rim perfectly straight and squarely, the flex of the brake arm will cause the rear edge of the brake shoe to do the brunt of the work. The front edge of the shoe may not even be engaging the rim under hard braking.

Good practice in installing brake shoes is to "toe them in", so that the front part of the shoe hits the rim first. As the brake arm flexes under real braking, it will permit the whole surface of the brake shoe to engage the rim.

Toeing in of brake shoes can also reduce the annoying squeal some brakes make when in use.

Brake shoes that are longer to the rear of the post will press more evenly on the rim. Most newer brake shoes have special washers with curved surfaces to allow you to adjust the angle of the shoe to the rim. Older brakes relied on brute force, typically bending the brake arm with an adjustable wrench. That is not a good idea with aluminum brakes-- it can initiate cracking, which leads to failure.

Also see Jobst Brandt's article on toe-in and brake squeal.

Tops

The parts of a drop handlebar above the brake levers.

Top Pull

A style of front derailer operated by a cable coming down from above, as opposed to a traditional "bottom-pull" unit, operated by a cable coming up from below. Top pull derailers are mainly used on mountain bikes, because they permit the designer to avoid running the gear cables by the bottom bracket, where they are exposed to spray from the front wheel.

Top-Swing ®

Most front derailers use a parallelogram which is fixed (attached to the derailer body) at the top, with the moveable cage attached to the bottom link of the parallelogram. Many of the newer Shimano units are built "upside down": the bottom of the parallelogram is fixed in place and the cage attaches to the top link.

A peculiarity of Top-Swing ® derailers is that the limit stop adjustment screws are reversed, so that the outer screw limits inward travel, and vice versa.

Top-Swing ® derailers clamp on to the seat tube lower down than bottom-swing units. (Shimano E-type derailers don't even attach to the seat tube, but are held on by the bottom bracket mounting ring.) Some frames made for use with top-swing derailers will not permit the installation of conventional bottom-swing derailers, because there's a bottle braze on in the way. Some suspension frames also require a top-swing front derailer for clearance reasons.

Top-Swing ® or bottom-swing derailers can be (and are) made in either top-pull or bottom-pull versions. (This has to do with the direction from which the cable approaches.)

Top Tube

The frame tube that runs horizontally from the top of the head tube to the seat cluster. Up until the 1980's, most high quality bicycles were built with the top tube exactly horizontal. Newer frame designs commonly have sloping top tubes, higher at the front. This is particularly common in smaller frame sizes.

The length of the top tube is probably the most important dimension in providing a comfortable fit. See my article on Frame Sizing.

Torsion, Torque

A force applied in the form of a twist, rather than a straight push or pull. "Torsion" is used to indicate that the force involved it a rotary force. "Torque" is a measurement of torsional force.

Torque is the linear force times the radius at which it is applied. For example, a 10-pound force applied two feet from the axis produces the same torque as a 2-pound force applied ten feet from the axis.

The standard units for measuring torque are pound-feet or Newton-meters. Note that the force unit goes first, so as not to be confused with energy/work measurements. A common error is to refer to "foot-pounds" instead of pound-feet of torque. This is not strictly correct, since the foot-pound is a unit of energy/work, not torque.

Also see the more extended article about torque.

Torque Wrench

A "torque wrench" is a type of wrench with a built-in spring-loaded indicator that gives a numerical readout of the amount of torque being applied through it.

This is primarily an automotive tool, especially useful for applications involving crushable gaskets which must be tightened evenly.

Torque wrenches are never needed for bicycle work, although they can be a useful training aid for inexperienced mechanics who haven't learned the feel of a properly-tightened fastener.

[I find this mostly to be true, but many bicycle components now are accompanied with spec sheets with lists of torque settings. There are three reasons for this:

• Consultants to attorneys measure torque values, leading to an excess of caution by the manufacturers
• Some components made of unusual materials (carbon fiber seatposts, aluminum bolts) require lower torque settings than for other parts of the same general type.
• In some unusual cases -- for example, quill handlebar stems -- a wedging effect multiplies the force exterted by a threaded part, and can lead to damage at torque values which would be normal otherwise.

This paragraph added by John Allen]

Also see the more extended discussion about torquing threaded parts.

Touring

"Touring" is a slippery word, and means different things to different people. This can cause miscommunication, so the word should be used with caution.

To non-cyclists, or casual cyclists, "touring" may mean riding 8 miles on a rented cruiser at a beach resort, or a fund-raising "thon" ride, or any type of riding where the principal objective is leisurely enjoyment of scenery and fresh air.

In the sense more generally accepted in cycling circles, however, a "tour" is a multi-day ride, which is not a competition or a timed event.

See also touring bicycle.

Touring Bag

A type of under-the-saddle bag popular in the British Isles. It attaches to special loops at the rear of the saddle, and also has a strap which wraps around the seatpost. Sometimes there is a special bracket instead to attach the bag to the saddle. This is necessary when the saddle does not have loops or has flimsy plastic loops, but it also allows the bag to be removed and replaced more quickly, and can keep a large bag up off the rear tire.

Traditional British touring bags are roughly cylindrical (oriented crossways-no attempt is made to make them aerodynamic) though they add little drag, because they are behind the cyclist. They come in a range of sizes, usually with a large main compartment and a small pocket at each end. They also feature metal rings on top of the flap to which the rider can strap a rolled-up rain cape, in case the rain stops.

Major brands are Brooks, Carradice, Karrimor and Zimbale. The better-quality bags are made of heavy black canvas, with gray"chrome" leather straps and corner reinforcements. In the USA, Dill Pickle Gear makes nice touring bags to order.

Most Brooks saddles have strong, steel bag loops. It may be necessary to rotate the springs of a sprung saddle so the straps will feed through easily past the coils. Loops can eventually cut through the straps, though some have smooth metal inserts. Brooks sells the eyelets, replacement part BYB 323, which will fit bag loops with a long, narrow (not triangular) slot.

A saddle without eyelets. The sharp edges of the bag loops can cut bag straps.

A saddle retrofitted with eyelets. Rotating the springs can make it easier to insert bag straps on a saddle with springs.

Filing the loops smooth can help. Carry a pair of extra toe straps to use as replacement straps, just in case.

Pop quiz: what's wrong with this picture?

Answer: the straps are threaded onto the springs, rather than through the bag loops -- but also, for the greatest stability, the buckles should be inside the bag, allowing it to be snugged up against the bag loops.

Straps inside bag.

Bag snugged up against loops.

Still, these bags are not ideal for cyclists who like to stand up and thrash their bicycles from side to side while climbing, due to sway. For the cyclist with a smooth riding style, these bags offer a good option for carrying a sizeable load on a bicycle which lacks pannier racks -- or to provide extra capacity.

This type of bag is currently enjoying a resurgence of popularity.

In case you might possibly have other questions about the picture, a further explanation is available.

Touring Bicycle

A touring bicycle is designed for comfort, durability, efficiency and, in most cases, load-carrying capacity. Touring bicycles fall into two major groupings:

1. Loaded-touring bicycles, the classic "touring" bicycle is intended for self-supported travel, including camping and, in some cases, cooking equipment. A loaded-touring bicycle has:

• A fairly laid-back fork angle for comfort and stability.
• Long chainstays, for stability, and to provide clearance between the rider's heels and the rear panniers.
• A triple chainwheel crankset, with a granny gear.
• A wide-range cluster, with a large sprocket as large or larger than the granny chainwheel.
• Sturdy wheels with wide (32-35 mm) tires.
• Cantilever brakes, to allow clearance for wide tires and fenders.
• Multiple braze-ons for bottle cages, racks, fenders, spare spokes, etc.

A well-equipped loaded-touring bicycle will usually have:

• Drop handlebars
• Full fenders.
• Front pannier rack (usually low-rider style.)
• Rear pannier rack.
• Lighting system (usually generator-powered.)
• 3 or 4 bottle cages, for water and cooking fuel.

Increasingly, loaded touring is being done on modified mountain bikes, which share many characteristics with loaded tourers.

Some riders prefer to use trailers instead of panniers to carry their camping equipment.

• Light-touring, or "credit-card" touring bicycles are intended for inn-to-inn tours, randonnées, or organized tours with sag-wagon service, in which the rider will carry perhaps a large touring bag or handlebar bag. A light-touring bicycle may be a modified road-racing bicycle, or a bicycle made for the purpose. It will usually have:
• Conservative road-racing geometry.
• A triple chainwheel crankset.
• A close- or medium-ratio cluster.
• Medium (25-28 mm) width tires.
• Clip-on aero bars.
• Clipless pedals.
• "Sport-touring" bicycles are not, strictly speaking, touring bicycles at all. This is a term normally used to refer to the general-purpose "ten-speeds" (later 12-speeds) of the '70's and early '80's. These bikes were marketed as general purpose machines, and millions were sold. Millions of them are now rusting away in the back of the garages of middle America. These bicycles are characterized by:
• 630 mm (27 inch) wheels.
• Drop handlebars
• Double chainwheels, usually 52/42 or 52/39.
• 5 speed freewheels, usually 14-28 teeth.

Since these bicycles were most often sold to people for whom drop handlebars were unsuited, many of them added features to try to make the bicycle more appealing to the casual cyclist, without losing the "racer" look:

• Extension levers for the brakes.
• Stem shifters.
• Foam handlebar padding. Note: the term "sport touring" is sometimes used to refer to a "light-touring" bike by cyclists too young to remember the 10-speed era.

Tourney

See Shimano Models

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