Search Search Search WWW

Down to next page


Up to previous page


A form of cantilever brake that works like a centerpull caliper. The "L"-shaped arms cross over above the tire, so the left brake shoe is operated by the right side of the transverse cable. A U-brake uses studs that are above the rim, rather than below the it, as with conventional cantilevers. They use the same type and placement of studs as rollercam brakes do.

In 1986-88 there was a fad for equipping mountain bikes with U-brakes mounted underneath the chain stays. This provided a nice clean look to the seat stay area of the bicycle, and provided a somewhat simpler cable routing. In addition, since the chain stays are larger and more rigid than typical seat stays, the "problem" of flexing of the studs under load was reduced. Conventional cantileves cannot be mounted on the chainstays, because the cantilevers would get in the way of the cranks.

Although U-brakes were cool looking and powerful, the fad died quite abruptly when people actually started using the bikes that were sold with chainstay-mounted U-brakes. They had several serious drawbacks:

In recent years U-brakes have been making a bit of a comeback on freestyle bikes.

Adjusting U-brakes:

First, remove the arms from the studs, make sure the studs are free of rust. Coat the studs liberally with grease (this is VERY important!)

Install the arms with them at their maximum spread and tighten the bolts that hold them to the frame. This is how you set the springs. Only connnect the transverse cable after this has been done.

There is usually a small setscrew on the side of one of the arms for fine adjustment of spring balance.

Set the transverse cable as short as possible for best braking. Check the brake shoe adjustment frequently--due to the location of the pivot studs on these brakes, as the brake shoes wear they hit higher and higher up on the rims. If you don't keep on top of the adjustment, they will eventually start rubbing on the tire sidewall. Many thousands of tires have been ruined by this.


Union Cycliste Internationale, the world-wide governing body of road and track racing.


Universal Chrome Plating, a process for chrome-plating cheap steel spokes so that they look shiny when they are new. U.C.P. spokes are used on low-end bicycles because they are cheaper than stainless steel spokes.

UD ®

See: Ultra-Drive

Ultegra ®

See Shimano Models

Ultra-Drive ®, (UD ®)

Campagnolo's equivalent to Hyperglide

Ultra Spacing

An early type of 6-speed freewheel made by Sun Tour, in which the sprockets were closer together than those of a 5-speed or normal 6-speed freewheel. This allowed the use of a 6-speed freewheel on a hub built for a 5-speed cluster, in a frame with 5-speed (120 mm) dropout spacing.

This was made possible by the development of chains in which the ends of the rivets did not protrude far past the side plates. 7- and 8-speed freewheels are also "Ultra" spaced, but the term is mainly used to describe the narrow 6-speed units.

Uniglide ®

An older Shimano buzzword for rear sprockets with twisted teeth for improved shifting. This was replaced by Hyperglide, a more sophisticated system of special sprocket tooth shapes.

See also my article on Shimano Cassettes.

Uniglide vs Hyperglide
Uniglide ®Hyperglide ®


Italian parts manufacturer, the leading Italian brake before Campagnolo entered the brake market.

Universal Joint

A mechanical linkage which allows two parts to flex with respect to one another, but not to rotate. The primary bicycle application of universal joints is for single-wheel trailers.



The act of shifting to a higher gear. In the case of derailer gearing, this means shifting to a smaller rear sprocket, or a larger chainwheel.


United States Cycling Federation, the principal governing body of bicycle racing in the U.S.


Under Seat Steering


Universal System Tubeless. The most common system of tubeless tires/rims for bicycle use.


A type of fork in which the upper ends of the blades bend together to attach directly to the steerer, eliminating a separate crown. This style of fork is common on mountain bikes and hybrids.

V1, V2 ®

Shimano Octalink ® cranks come in one of two different spline patterns:

Square Taper, Octalink V1 and V2, ISIS Bottom Brackets


The part of the inner tube that permits air to be added. There are three types used on bicycles, Presta, Schrader, and Woods
Schrader Presta Woods
Schrader valvePresta valveWoods valve
If you want to convert a rim drilled for Presta valves to accept Schrader valves, drill it out with a 21/64" drill bit.

Valve Cap

A metal or plastic screw-on cover intended to protect the innards of a tire valve from dust and other foreign matter.

In the case of Presta valves, which have non-removeable, built-in caps, external caps are unnecessary in use. The purpose of these redundant caps that come with Presta tubes and tubulars is so that the pointy end of the valve won't puncture your spare tube or tubular while it is rolled up. There's no reason to use them in actual riding

V-Brake ®

A Shimano trademark for a direct-pull cantilever brake. This is a cantilever which does not use a separate transverse cable. It has two tall arms, one of which has a housing stop and the other an anchor bolt. The exposed part of the cable runs horizontally from one arm to the other.

V-Brakes and other direct-pull cantilevers have more mechanical advantage than other brakes, so they require special hand levers with less-than-average mechanical advantage to keep the overall mechanical advantage in a useful range.

Some V-Brakes also incorporate a parallelogram linkage which mantains the shoe at the correct angle as it approaches the rim. This feature also allows the motion of the shoe to be more nearly horizontal than conventional cantilevers.

"V-Brake" is a Shimano trademark.


French for "bicycle", commonly used as a root for compound words relating to cycling. Short form of "vélocipede."


A bicycle racing track.


Japan Vehicle Inspection Association, a quasi-official agency that promotes standardization and minimum quality standards for Japanese vehicles.

In the post WW2 era, most Japanese industries acquired similar governing bodies under the J.I.S.C. (Japanese Industrial Standards Committee). These agencies helped to turn around the international reputation of Japanese products from the former stereotype of cheap copies of western designs to their present high reputation for quality and reliability.


The opposite of "virtue."

Also, British spelling of "vise ."


A very useful tool for holding parts solidly to a workbench. A good vise, bolted to a solid workbench, is one of the most basic requirements of a well equipped work area.

Vise-Grip ®

A type of locking pliers. It has a toggle link mechanism in one leg, and an adjusting thumbscrew in one of the legs. Vise-Grips are operated much the same as quick-release mechanisms.

This is a tool of last resort for removing nuts or bolts whose heads are so badly damaged that the proper wrench will not fit them. They should not be used on un-damaged fasteners, because their serrated jaws will damage the part they are used on.

Down to next page


Spoke divider

Feedback? Questions?

Articles by Sheldon Brown and others
Beginners Brakes Commuting
Fixed Gear
Frames Gears &
Tandems Touring What's
Wheels Sheldon

Accessories Bicycles Parts Specials Tools

Since May 4, 1996

Copyright © 1996, 2007 Sheldon Brown

Back to Harris Cyclery Home Page

If you would like to make a link or bookmark to this page, the URL is:

If you would like to make a link or bookmark to this glossary, the URL is:

If you would like to make a link or bookmark to a specific definition, that's fine too. I am committed to keeping the urls stable, so I won't be breaking your link.