Search sheldonbrown.com and sheldonbrown.org

Sheldon Brown photo

Sheldon Brown's Bicycle Glossary Ri-Rz

This glossary is also available in pdb format for your Palm OS PDA Palm

A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z

Up to previous page

Ribbon
Handlebar tape. This is a mistranslation of "ruban", and should be avoided--"tape" is the correct English term.
Rigid
A frame or fork which does not have any built in mechanical suspension system. Conventional forks actually are designed to flex slightly over bumps, but they are still called "rigid" forks as compared with true suspension forks.
Rim
The outer metal hoop of a bicycle wheel. The rim does not include the spokes, or the hub.
Rim Cut
A pinch flat, or the damage suffered by the tire sidewall from similar causes.
Rise
In an upright handlebar, the "rise" is the vertical distance from the low point of the bar (the middle) and the high points (typically the grip area.)
Rivet
A rivet is a cylindrical fastener which fits through a tight-fitting hole. The end of the rivet is then hammered or "peened" over so that it spreads out like a mushroom, so that the rivet will stay in place. Generally, rivets are one-time fasteners, for parts which are not expected to be disassembled for servicing.

Rivets are commonly used to assemble derailers, fenders and saddles. They are also used to assemble low-quality pedals and cranks/chainwheels.

The links of a bicycle chain are held together by rivets (sometimes also called "link pins") which, in most cases only have a slight thickening at the ends, rather than a seriously spread head. This allows chain links to be disassembled by partially removing the rivet, then driving the rivet back in with a chain tool. The narrowest chains used can not be reassembled with a chain tool, but rather, must be reassembled using a special replacement rivet or master link.

Road Bicycle
In the broadest sense, this would refer to any bicycle designed to be ridden primarily on pavement.

Usually, the term "road bicycle" is used to refer to a sport bicycle with drop handlebars and narrow tires. Sometimes the term is used in an even more restrictive sense, to apply to a road racing bicycle.

Road Racing
In one sense, road racing is any racing that is done on roads, but the more usual sense is that of a mass-start race from one place to another, or possibly a loop course with long laps (as opposed to a criterium.) Since road races tend to be longer than criteriums, and the packs tend to be smaller and less dense than those in criteriums, bicycles designed for road racing tend to favor comfort more than criterium machines do, but to be less maneuverable. They may have lower bottom brackets, since there is less need to pedal through corners in a road race than there is in a short-course criterium.
Roadster
A traditional type of utility bicycle, sometimes known as a "postman's bike". These usually have 37-635 (28 x 1 1/2) wheels, rod brakes, a chain case, slack angles. Most of them are black. This is the predominant type of bicycle in Asia and the Netherlands (although Dutch roadsters are more likely to have rod-operated drum brakes)

superb 54
Click for larger image. (64k)

See my articles on English 3-Speeds, and my 1954 Superbe Roadster (pictured above.)

Rod Brake
Roller-lever brake. Some rod brakes use the rods to operate a drum brake; this set-up is popular in the Netherlands.

Most rod brakes use a "stirrup" which holds brake shoes that pull against the inner circumference of the rim. These are usually used with Westwood or Raleigh pattern rims, which have a ridge where the spokes attach, so there is no risk of snagging a spoke nipple with the brake shoes. These brakes are relatively trouble-free, but slight irregularities in rim radius can cause a brake to grab. Unless a rim is dented, caliper brakes that bear on the rim sidewalls are, on the other hand, very tolerant, because the rim's width remains constant even if the wheel is out of true. This is especially so with rims that have parallel sidewalls, including the Westrick rims used on higher-end Raleigh Industries three-speeds for many decades, and most aluminum rims made since 1980..

Rohloff
Rohloff is a German company, a maker of high quality chains and tools, but best known for the Rohloff Speedhub, a 14-speed internal gear hub.

The Rohloff Speedhub has an unusually wide gear range.

Rollers
A treadmill-like device for riding a bicycle indoors. Consists of a framework with 3 rollers. The front wheel rests on top of one of the rollers, and the rear wheel sits between two of them. The front roller is connected to one of the rear rollers, so that as the rear wheel turns its rollers, the belt makes the front roller turn with them. This allows the bicycle to be "steered" within the width of the rollers, and allows the bicycle to be balanced as if it were being ridden on the road.

Compared with a stationary trainer, rollers have the advantage of forcing a cyclist to ride in a very smoothly, and generally improve form and smoothness on the bike. For most riders, however, a stationary trainer allows a higher intensity of riding, since it requires no mental effort to stay balanced.

Mastering roller riding is tricky. It is helpful to start out with the rollers in a doorway, so it is possible to lean against the door frame to prevent a fall.

It is also useful to have a full-length mirror straight ahead, so that you can observe your form.

If you are having trouble learning to balance on rollers, make sure that you are looking straight ahead, not down at the rollers. It is much harder to balance if you look down.

It is also a very good idea to set up a fan to help cool you off, as the slipstream does when riding outdoors -- or to set up your rollers in a cold place. That is often easy to arrange, as rollers are typically used for winter training..

Roller Bearing
A bearing that uses cylindrical or conical rollers instead of balls. The major bicycle application of roller bearings is in some headsets. Roller-bearing headsets are very long-lasting, due to the greater contact surface area as opposed to ball bearings. Current units, however do not turn as freely as ball bearing headset. due to the use of cylindrical rollers, rather than conical rollers. Cylindrical rollers do not naturally roll in a circle, but in a straight line.

Roller bearings also are used in some pedals and for the planet pinions of some internal-gear hubs.

Rollerbrake ®
A Shimano trademark for a variant form of hand-operated drum brake. It uses a ring of rollers pushed outward by a cam to engage the brake shoe with the drum. The cam is operated by a cable from a hand lever.

These brakes are prone to fading due to overheating if used in mountainous terrain.

I particularly advise against using a front Rollerbrake, because the front hubs made for these brakes incorporate the infamous and wrong-headed "Power Modulator " mechanism which reduces the effectiveness of the brake.

Also see the article about Rollerbrakes on this site.

Roller-cam Brake
A type of brake which uses a triangular cam. It has two see-saw like arms, pivoted in the middle on cantilever-type studs. The cam is pulled by the cable, which is attached to the narrow end. As the cam is pulled, its sloping sides push outward on rollers which are attached to the upper end of the brake arms. Roller-cam brakes permit the use of variable ratios by making the sides of the cam curve instead of being straight. Typically this is done to make the shoes travel in toward the rim fast, then more slowly as they engage...this gives more mechanical advantage in the actual braking range of travel, while allowing the shoes to back off farther from the rim than if the mechanical advantage were consistent throughout the travel range.

Compared to normal cantilevers, roller-cams have the advantage of not protruding past the sides of the frame, which made them popular in the late '80's when there was a fad for placing the rear brake under the chainstays...you couldn't use conventional cantilevers there, because the cranks would bump into them.

Unfortunately, roller-cams are more difficult to set up than conventional cantilevers, and they make for more-difficult wheel changes.

Roller-cam cantilevers do not work on cantilever studs made for conventional cantilevers, because conventional cantilever studs are mounted inward from the rim, while roller-cam studs are outward from the rim. "U-brake" cantilevers are interchangeable with roller-cams.

With both roller-cams and U-brakes, there is a tendency for the brake shoes to strike higher and higher on the rim as the pads wear. If the pads are not checked regularly, they eventually start to rub on the sidewall of the tire, destroying the tire in short order.

The Odyssey "Pitbull" is a caliper-type roller-cam unit, popular in BMX and recumbent applications.

Roller Chain
Standard bicycle chain has rollers that smooth the engagement of the chain with the sprockets, as opposed to block chain.
Roller Clutch
A roller clutch (or "silent clutch" in Shimano terminology) is a type of freewheel ratchet mechanism which uses cams and rollers instead of pawls. It has been used in some cassettes and internal-gear hubs, notably in the Shimano Nexus and Alfine series.

In addition to eliminating the annoying "tick-tick-tick" of a pawl-type freewheel, a roller clutch has less slop when drive force is applied to it...drive begins as soon as forward motion of the pedals starts, unlike a pawl-type freewheel which only drives once it has rotated far enough to let the pawls engage the notches of the ratchet ring.

Roller-lever Brake
A hand-operated brake that uses solid rods and pivots as a linkage from the handlebar to the brake unit. Roller-lever brakes are harder to work on than brakes operated by Bowden cables, but they are more reliable than cables, especially on bicycles which are subject to neglect and abuse. They are commonly found on roadsters. See also Rod Brake.
Rolling Resistance
The friction caused by the flexing of the tire and tube as it deforms under load, and of the wheel bearings. For a given tire, rolling resistance will vary considerably with the inflation pressure: the higher the pressure, the lower the rolling resistance. The rolling resistance of the tire and tube is typically far higher than that of the bearings.
Rollout
The distance a bicycle travels in one complete revolution of the cranks; development. This number is used in describing drive ratios and in calibrating bicycle computers.
Rotor
A mechanism used on freestyle bicycles to route the rear brake cable through a bearing assembly which surrounds the handlebar stem. This allows the handlebars and fork to revolve indefinitely without fouling the rear brake cable. See also Potts modification. Probably the best rotor currently available is the Odyssey Gyro ®
R.P.M.
Revolutions Per Minute, a measure of speed of rotation. In bicycling, this is most often used in discussions of pedaling cadence.
RSX
See Shimano Models and Buzzwords
RX-100
See Shimano Models and Buzzwords

Down to next page

A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z

Spoke Divider

Articles by Sheldon Brown and others
Harris
Home
Beginners Brakes Commuting
Lights
Cycle-
Computers
Do-It-
Yourself
Essays
Family
Cycling
Fixed Gear
Singlespeed
Frames Gears &
Drivetrain
Bicycle
Humor
Bicycle
Glossary
Bicycle
Links
Old
Bikes
Repair
Tips
Tandems Touring What's
New
Wheels Sheldon
Brown

Accessories Bicycles Parts Specials Tools

Copyright © 1996, 2008 Sheldon Brown

Harris Cyclery Home Page

If you would like to make a link or bookmark to this page, the URL is:
http://sheldonbrown.com/gloss_ri-z.html

If you would like to make a link or bookmark to this glossary, the URL is:
http://sheldonbrown.com/glossary

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.

Last Updated: by John Allen


blank

blank

blank

blank

blank