Spoon brakes The
spoon brake or
plunger brake was probably the first type of bicycle brake and precedes the pneumatic tyre. Spoon brakes were used on
penny farthings with solid rubber tyres in the 1800s and continued to be used after the introduction of the pneumatic-tyred safety bicycle. The spoon brake consists of a pad (often leather) or metal shoe (possibly rubber faced), which is pressed onto the top of the front tyre. These were almost always rod-operated by a right-hand lever. In
developing countries, a foot-operated form of the spoon brake sometimes is retrofitted to old
rod brake roadsters. It consists of a spring-loaded flap attached to the back of the fork crown. This is depressed against the front tyre by the rider's foot. Perhaps more so than any other form of bicycle brake, the spoon brake is sensitive to road conditions and increases tyre wear dramatically. Though made obsolete by the introduction of the Duck brake, coaster brake, and rod brake, spoon brakes continued to be used in the
West supplementally on adult bicycles until the 1930s, and on children's bicycles until the 1950s. In the developing world, they were manufactured until much more recently. File:Bicycle spoon brake on 1886 Swift Safety Bicycle at Coventry Transport Museum.png|Spoon brake on front wheel of 1886 Swift Safety Bicycle at Coventry Transport Museum File:Bicycle spoon brake variation.jpg|Spoon brake variation at the Batavus Museum in Heerenveen, Netherlands File:Bicycle spoon brake on 1898 Columbia Model 51 Ladies Chainless.png|Bicycle spoon brake on 1898 Columbia Model 51 Ladies Chainless File:Antique 1 (Brake detail).jpg|Spoon brake on front wheel File:Marian038.jpg|Improvised spoon brake on a Chinese cargo tricycle
Duck brake Invented in 1897, the
Duck brake or
Duck roller brake used a rod operated by a lever on the handlebar to pull twin friction rollers (usually made of wood or rubber) against the front tyre. Known colloquially as the
duck brake, the design was used by many notable riders of the day, and was widely exported to England, Australia, and other countries. In 1902, Louis H. Bill was granted a patent for an improved version of the Duck Roller Brake (Patent 708,114) for use on
motorized bicycles (motorcycles).
Rim brakes Rim brakes are so called because braking force is applied by friction
pads to the
rim of the rotating wheel, thus slowing it and the bicycle. Brake pads can be made of
leather,
rubber, or
cork and are often mounted in
metal "
shoes". Rim brakes are typically actuated by a
lever mounted on the
handlebar.
Advantages and disadvantages rim worn out by V-brakes. The outer wall has been worn through and the wheel is dangerously weakened. This is a disadvantage of rim brakes. Rim brakes are inexpensive, light, mechanically simple, easy to maintain, and powerful. However, they perform relatively poorly when the
rims are wet, and will brake unevenly if the rims are even slightly warped. Because rims can carry debris from the ground to the brake pads, rim brakes are more prone to clogging with mud or snow than disc brakes (where braking surfaces are higher from the ground), particularly when riding on unpaved surfaces. The low price and ease of maintenance of rim brakes makes them popular in low- to mid-price commuter bikes, where the disadvantages are alleviated by the unchallenging conditions. The light weight of rim brakes also makes them desirable in road racing bicycles. Rim brakes require regular maintenance. Brake pads wear down and have to be replaced. As they wear down, their position may need to be adjusted as the material wears away. Because the motion of most brakes is not perfectly horizontal, the pads may lose their centering as they wear, causing the pads to wear unevenly. Over longer time and use, rims can become worn. Rims should be checked for wear periodically as they can fail catastrophically if the braking surface becomes too worn. Wear is accelerated by wet and muddy conditions. Rim brakes require that the rims be straight (not out-of-round or warped). If a rim has a pronounced wobble, then the braking force may be intermittent or uneven, and the pads may rub the rims even when the brake is not applied. During braking, the friction surfaces (brake pads and rims) will experience thermal heating. In normal use this is not a problem, as the brakes are applied with limited force and for a short time, so the heat quickly dissipates to the surrounding air. However, on a heavily laden bike on a long descent, heat energy may be added more quickly than it can dissipate causing heat build-up, which may damage components and cause brake failure. A ceramic coating for the rims is available which may reduce wear and can also improve both wet and dry braking. It may also slightly reduce heat transfer to the inside of the rims because it is a thermal insulator.
Brake pads Brake pads are available with numerous shapes and materials. Many consist of a replaceable rubber pad held on a mounting, or
brake shoe, with a post or bolt on the back to attach to the brake. Some are made as one piece with the attachment directly molded in the pad for lower production costs; brake pads of the
cartridge type are held in place by a metal
split pin or threaded
grub screw and can be replaced without moving the brake shoe from its alignment to the rim. The rubber can be softer for more braking force with less lever effort, or harder for longer life. Many pad designs have a rectangular shape; others are longer and curved to match the radius of the rim. Larger pads do not necessarily provide more braking force, but will wear more slowly (in relation to thickness), so can usually be thinner. In general, a brake can be fitted with a variety of pads, as long as the mounting is compatible. Carbon fiber rims may be more sensitive to damage by incorrectly matched brake pads, and generally must use non-abrasive cork pads. Ceramic-coated rims should be used with special pads because of heat build-up at the pad-rim interface; standard pads can leave a "glaze" on the ceramic braking surface, reducing its inherent roughness and leading to a severe drop in wet-weather braking performance. Ceramic pads usually contain chromium compounds to resist heat. For wet-weather use, brake pads containing iron (iii) oxide are sometimes used as these have higher friction on a wet aluminum rim than the usual rubber. These salmon-colored pads were first made by Scott-Mathauser and are now produced by Kool-Stop. To minimise excessive rim wear, a brake pad should be hard enough that it does not embed road grit or chips of rim metal in the face of the pad, since these act as grinding/gouging agents and markedly reduce rim life.
Types of rim brakes The following are among the many sub-types of rim brakes:
Rod-actuated brakes The
rod-actuated brake, or simply
rod brake (
roller lever brake in Raleigh terminology), uses a series of rods and pivots, rather than
Bowden cables, to transmit force applied to a hand lever to pull friction pads upwards against the inner surface, which faces the hub, of the wheel rim. They were often called "stirrup brakes" due to their shape. Rod brakes are used with a rim profile known as the
Westwood rim, which has a slightly concave area on the braking surface and lacks the flat outer surface required by brakes that apply the pads on opposite sides of the rim. The rear linkage mechanism is complicated by the need to allow rotation where the
fork and handlebars attach to the frame. A common setup was to combine a front rod brake with a rear coaster brake. Although heavy and complex, the linkages are reliable and durable and can be repaired or adjusted with simple hand tools. The design is still in use, typically on African and Asian
roadsters such as the
Sohrab and
Flying Pigeon.
Caliper brakes The
caliper brake is a class of
cable-actuated brake in which the brake mounts to a single point above the wheel, theoretically allowing the arms to auto-centre on the rim. Arms extend around the tyre and end in brake shoes that press against the
rim. While some designs incorporate dual pivot points — the arms pivot on a sub-frame — the entire assembly still mounts to a single point. Caliper brakes tend to become less effective as tyres get wider, and so deeper, reducing the brakes'
mechanical advantage. Thus caliper brakes are rarely found on modern
mountain bikes. But they are almost ubiquitous on
road bikes, particularly the
dual-pivot side-pull caliper brake.
Side-pull caliper brakes brake.
Single-pivot side-pull caliper brakes consist of two curved arms that cross at a pivot above the wheel and hold the brake pads on opposite sides of the rim. These arms have extensions on one side, one attached to the cable, the other to the cable housing. When the brake lever is squeezed, the arms move together and the brake pads squeeze the rim. These brakes are simple and effective for relatively narrow tyres but have significant flex and resulting poor performance if the arms are made long enough to fit wide tyres. If not adjusted properly, low quality varieties tend to rotate to one side during actuation and tend to stay there, making it difficult to evenly space brake shoes away from the rim. These brakes are now used on inexpensive bikes; before the introduction of dual-pivot caliper brakes they were used on all types of road bikes.
Dual-pivot side-pull caliper brakes are used on most modern
racing bicycles. One arm pivots at the centre, like a side-pull; and the other pivots at the side, like a centre-pull. The cable housing attaches like that of a side-pull brake. These brakes offer a higher
mechanical advantage, and result in better braking. Dual-pivot brakes are slightly heavier than conventional side-pull calipers and cannot accurately track an out-of-true rim, or a wheel that flexes from side to side in the frame during hard climbing. It is common to see professional racers climbing mountains with the quick-release undone on the rear brake, to eliminate drag from this source.
Direct mount rim brakes employ two mounting points, increasing stiffness and braking power. It was developed by
Shimano and released as an
open standard. Individual mounting points for each arm ease the centering of side-pull brakes, and accommodate tire widths of 30 mm and more.
Centre-pull caliper brakes Centre-pull caliper brakes have symmetrical arms and therefore centre more effectively. The cable housing attaches to a fixed cable stop attached to the frame, and the inner cable bolts to a sliding piece (called a "braking delta", "braking triangle", or "
yoke") or a small pulley, over which runs a
straddle cable connecting the two brake arms. Tension on the cable is evenly distributed to the two arms, preventing the brake from taking a "set" to one side or the other. These brakes were reasonably priced, and in the past filled the price niche between the cheaper and the more expensive models of side-pull brakes. They are more effective than side-pull brakes in long reach applications as the distance between the pivot and brake pad or cable attachment is much shorter, reducing flex. It is important that the fixed bridge holding the pivots is very stiff.
U-brakes U-brakes (also known by the trademarked term
990-style) are essentially the same design as the
centre-pull caliper brake. The difference is that the two arm pivots attach directly to the frame or fork while those of the centre-pull caliper brake attach to an integral bridge frame that mounts to the frame or fork by a single bolt. Like
roller cam brakes, this is a caliper design with pivots located above the rim. Thus U-brakes are often interchangeable with, and have the same maintenance issues as, roller cam brakes. U-brakes were used on mountain bikes through the mid-to-late 1980s, particularly under the chain stays, a rear brake mounting location that was then popular. This location usually benefits from higher frame stiffness, an important consideration with a powerful brake since flex in the stays will increase lever travel and reduce effective braking force. Unfortunately it is also very prone to clogging by mud, which meant that U-brakes quickly fell out of favour on cross-country bikes. U-brakes are the current standard on
Freestyle BMX frames and forks. The U-brake's main advantage over cantilever and linear-pull brakes in this application is that sideways protrusion of the brake and cable system is minimal, and the exposed parts are smooth. This is especially valuable on freestyle BMX bikes where any protruding parts are susceptible to damage and may interfere with the rider's body or clothing.
Cantilever brakes The
cantilever brake is a class of brake in which each arm is attached to a separate pivot point on one side of the
seat stay or
fork. Thus all cantilever brakes are dual-pivot. Both first- and second-class
lever designs exist; second-class is by far the more common. In the second-class lever design, the arm pivots below the rim. The brake shoe is mounted above the pivot and is pressed against the rim as the two arms are drawn together. In the first-class lever design, the arm pivots above the rim. The brake shoe is mounted below the pivot and is pressed against the rim as the two arms are forced apart. Due to a wider possible distance between the mounts and pads, cantilever brakes are often preferred for bicycles that use wide tyres, such as on
mountain bikes. Because the arms move only in their designed arcs, the brake shoe must be adjustable in several planes. Thus cantilever brake shoes are notoriously difficult to adjust. As the brake shoes of a second-class cantilever brake wears, they ride lower on the rim. Eventually, one may go underneath the rim, so that the brake does not function. There are several brake types based on the cantilever brake design:
cantilever brakes and
direct-pull brakes – both second class lever designs – and
roller cam brakes and
U-brakes – both first class lever designs.
Traditional cantilever brakes Traditional cantilever brakes pre-date the
direct-pull brake. It is a centre-pull cantilever design with an outwardly angled arm protruding on each side, a cable stop on the frame or fork to terminate the cable housing, and a straddle cable between the arms similar to
centre-pull caliper brakes. The cable from the brake lever pulls upwards on the straddle cable, causing the brake arms to rotate up and inward thus squeezing the rim between the brake pads. Originally, cantilever brakes had nearly horizontal arms and were designed for maximum clearance on touring or cyclo-cross bicycles. When the mountain bike became popular, cantilever brakes were adopted for these too, but the smaller MTB frames meant that riders often fouled the rear brake arms with their heels. "Low profile" cantilevers were designed to overcome this, where the arms are closer to 45 degrees from horizontal. Low profile brakes require more careful attention to cable geometry than traditional cantilevers but are now the most common type. Traditional cantilever brakes are difficult to adapt to bicycle suspension and protrude somewhat from the frame. Accordingly, they are usually found only on bicycles without suspension.
V-brakes Linear-pull brakes or
direct-pull brakes, commonly referred to by Shimano's trademark
V-brakes, are a side-pull version of
cantilever brakes and mount on the same frame
bosses. However, the arms are longer, with the cable housing attached to one arm and the cable to the other. As the
cable pulls against the housing, the arms are drawn together. Because the housing enters from vertically above one arm yet force must be transmitted laterally between arms, the flexible housing is extended by a rigid tube with a 90° bend known as the "noodle" (a noodle with a 135° bend is used where the front brake is operated by the right hand, as this gives a smoother curve in the cable housing). The noodle is seated in a stirrup attached to the arm. A flexible bellows often covers the exposed cable. Since there is no intervening mechanism between the cable and the arms, the design is called "direct-pull". And since the arms move the same distance that the cable moves with regard to its housing, the design is also called "linear-pull". The term "V-brake" is trademarked by Shimano and represents the most popular implementation of this design. Some high-end V-brakes use a four-pivot parallel motion so the brake pads contact at virtually the same position on the wheel rim regardless of wear. V-brakes function well with the suspension systems found on many mountain bikes because they do not require a separate cable stop on the frame or fork. Because of the higher mechanical advantage of V-brakes, they require brake levers with longer cable travel than levers intended for older types of brakes. Mechanical (i.e. cable-actuated) disc brakes use the same amount of cable travel as V-brakes, except for those that are described as being "road" specific. As a general rule, mechanical disc brakes for so-called "flat bar" bicycles (chiefly mountain and hybrid bicycles) are compatible with V-brake levers, whereas mechanical disc brakes intended for "drop-bar" bicycles are compatible with the cable pull of older brake designs (cantilever, caliper, and U-brake). Poorly designed V-brakes can suffer from a sudden failure when the noodle end pulls through the metal stirrup, leaving the wheel with no braking power. Although the noodle can be regarded as a service item and changed regularly, the hole in the stirrup may enlarge through wear. The stirrup cannot normally be replaced, so good-quality V-brakes use a durable metal for the stirrup. There is much in favor of the roller cam brake design. Since the cam controls the rate of closure, the clamping force can be made non-linear with the pull. And since the design can provide positive
mechanical advantage, maximum clamping force can be higher than that of other types of brakes. They are known for being strong and controllable. On the downside, they require some skill to set up and can complicate wheel changes. They also require maintenance: like
U-brakes, as the pad wears it strikes the rim higher; unless re-adjusted it can eventually contact the tyre's sidewall. The roller cam design was first developed by
Charlie Cunningham --> Roller cam brakes were used on early
mountain bikes in the 1980s and into the 1990s, mounted to the
fork blades and
seat stays in the standard locations, as well as below the
chain stays for improved stiffness as they do not protrude to interfere with the
crank. It is not unusual for a bicycle to have a single roller cam brake (or
U-brake) combined with another type. They are still used on some
BMX and
recumbent bicycles. There are two rare variants that use the roller cam principle. For locations where centre-pull is inappropriate, the side-pull toggle cam brake was developed. Also a first-class cantilever, it uses a single-sided sliding cam (the toggle) against one arm that is attached by a link to the other arm. As the cam presses against the follower, the force is also transmitted to the other arm via the link. And specifically for suspension forks where the housing must terminate at the brake frame, the side-pull "sabre cam brake" was developed. In the sabre cam design, the cable end is fixed and the housing moves the single-sided cam.
Delta brakes delta brakes The
delta brake is a road bicycle brake named due to its triangular shape. The cable enters at the centre, pulls a corner of a parallelogram linkage housed inside the brake across two opposite corners, pushing out at the other two corners on to the brake arms above the pivots, so that the arms below the pivots push pads in against the rim. A feature of the design is that the
mechanical advantage varies as a tangent function across its range, where that of most other designs remains fixed. Many consider the brake attractive, and it has a lower wind profile than some other common brakes. However,
Bicycle Quarterly criticized the delta brake for being heavy, giving mediocre stopping power, and suffering disadvantageous variable mechanical advantage. In particular, with a small parallelogram, pad wear causes mechanical advantage to rise dramatically. However, with high leverage, the stroke of the lever is not enough to fully apply the brake, so the rider can have brakes that feel normal in light braking but which cannot be applied harder for hard braking. The basic design dates from at least the 1930s. They were made most prominently by
Campagnolo in 1985, but brakes based on the same mechanism were also manufactured by Modolo (Kronos), , and others. but this is no longer the case.
Single vs. dual actuation Many disc brakes have their pads actuated from both sides of the caliper, while some have only one pad that moves. Dual actuation can move both pads relative to the caliper, or can move one pad relative to the caliper, then move the caliper and other pad relative to the rotor, called a "floating caliper" design. Single-actuation brakes use either a multi-part rotor that floats axially on the hub, or bend the rotor sideways as needed. Bending the rotor is theoretically inferior, but in practice gives good service, even under high-force braking with a hot disc, and may yield more progressiveness.
Multiple pistons For disc brakes with a hydraulic system, high-performance calipers usually use two or three pistons per side; lower-cost and lower-performance calipers often have only one per side. Using more pistons allows a larger piston area and thus increased leverage with a given master cylinder. Also, pistons may be of several sizes so pad force can be controlled across the face of the pad, especially when the pad is long and narrow. A long narrow pad may be desired to increase pad area and thus reduce the frequency of pad changes. In contrast, a single large piston may be heavier.
Caliper mounting standards There are many standards for mounting disc brake calipers. However, most manufactures today use either the
IS or
post-mount (PM) standards. These differ by disc size and axle type. In 2014
Shimano introduced a "Flat Mount" standard for high end road bikes and uses it exclusively for its top tier brake calipers.
Advantages and disadvantages of various types of mounts A disadvantage of post mounts is that the bolt is threaded directly into the fork lowers. If the threads are stripped or if the bolt is stuck, then the threads will need to be repaired, or the seized bolt drilled out. Frame manufacturers have standardized the IS mount for the rear disc brake mount. In recent years post mount has gained ground and is becoming more common. This is mostly due to decreased manufacturing and part cost for the brake calipers when using post mount. A limitation of the mount is that the location of the rotor is more constrained: it is possible to encounter incompatible hub/fork combinations, where the rotor is out of range.
Disc mounting standards There are many options for rotor mounting. Standard International Standard (IS) six‑bolt disc brake rotors are typically secured to hubs with M5×10 mm bolts that use a
Torx T25 head. IS is a six-bolt mount and is the
industry standard. Center Lock is patented by Shimano and uses a
splined interface along with a
lockring to secure the disc. The advantages of Center Lock are that the splined interface is theoretically stiffer, and removing the disc is quicker because it only requires one lockring to be removed. Some of the disadvantages are that the design is patented requiring a licensing fee from Shimano. A Shimano cassette lockring tool (or an external
BB tool in case of through-axle hub) is needed to remove the rotor and is more expensive and less common than a Torx key. Advantages of IS six-bolt are that there are more choices when it comes to hubs and rotors. Coaster brakes have the advantage of being protected from the elements and thus perform well in rain or snow. Though coaster brakes generally go years without needing maintenance, they are more complicated than rim brakes to repair if it becomes necessary, especially the more sophisticated type with expanding brake shoes. Coaster brakes also do not have sufficient heat dissipation for use on long descents, a characteristic made legendary through events such as the 'Repack
Downhill' race, where riders almost certainly would need to repack their coaster brakes after the grease melted or smoked due to the heat from lengthy downhill runs. A coaster brake can only be applied when the cranks are reasonably level, limiting how quickly it can be applied. As coaster brakes are only made for rear wheels, they have the disadvantage common to all rear brakes of skidding the wheel easily. This disadvantage may, however, be alleviated if the bicycle also has a hand-lever-operated front brake and the cyclist uses it. Another disadvantage is that the coaster brake is completely dependent on the chain being fully intact and engaged. If the chain breaks or disengages from the chainwheel and/or rear sprocket, the coaster brake provides no braking power whatsoever. Like all hub brakes except disc brakes, a coaster brake requires a reaction arm to be connected to the frame. This may require unbolting when the wheel is removed or moved in its fork ends to adjust chain tension.
Drag brakes A
drag brake is a type of brake defined by its use rather than by its mechanical design. A drag brake is intended to provide a constant decelerating force to slow a bicycle on a long downhill rather than to stop it; a separate braking system is used to stop the bicycle. A drag brake is often employed on a heavy bicycle such as a tandem in mountainous areas where extended use of rim brakes could cause a rim to become hot enough to
blow out.; The typical drag brake has long been a
drum brake. The largest manufacturer of this type of brake is
Arai, whose brakes are screwed onto hubs with conventional freewheel threading on the left side of the rear hub and operated via
Bowden cables. As of 2011, the Arai drum brake has been out of production for several years, with remaining stocks nearing depletion and used units commanding premium prices on internet auction sites. More recently, large-rotor
disc brakes are being used as drag brakes. (Some tandem riders with Avid BB-7 mechanical disc brakes and 203 mm rotors report fewer heat problems under heavy braking than when using the previous standard of comparison, an Arai drum used as a drag brake.) DT-Swiss make an adapter to mate disc rotors with hubs threaded for the Arai drum brake, but this still leaves the problem of fitting the caliper.
Band brake A
band brake consists of a band, strap, or cable that wraps around a
drum that rotates with a wheel and is pulled tight to generate braking friction. Band brakes appeared as early as 1884 on tricycles. A
rim band brake, as implemented on the
Yankee bicycle by Royce Husted in the 1990s, consists of a stainless-steel cable, wrapped in a
kevlar sheath, that rides in a u-shaped channel on the side of the wheel rim. Squeezing the brake lever tightens the cable against the channel to produce braking friction.{{cite web ==Actuation mechanisms==