Most modern racing-style road bikes use brakes referred to as dual-pivot caliper brakes. These brakes have a compact "C" shape, with a brake cable that extends vertically from one side of the caliper. They usually have a small, rotating release lever that allows you to temporarily open the caliper for wheel installation and removal.
The road brake caliper mounts to the frame using a single bolt, either through the fork crown on the front, or through the seat stay bridge on the rear.
Dual-pivot calipers are lightweight and very easy to adjust and service. Their only downside is that they are only appropriate for very skinny-tired road bikes; they usually do not have enough clearance to accomodate wider touring, hybrid, or off-road tires. Fender installation with road caliper brakes can be a challenge as well, although some road-specific fenders are available that can work in some cases.
Disc brakes have become a popular option on mountain bikes for many years, and recently are starting to become more common on hybrids, some road touring bikes, and most recently, some cyclocross bikes.
Disc brakes typically provide the best stopping power in all conditions, even in the rain or mud, since the moisture, mud, and other debris has less of a tendency to collect on the braking surface compared to rim brakes.
A bike's frame and fork must have disc brake mounting tabs, so it's difficult (usually impossible) to retrofit and older bike with disc brakes. The hubs on the wheels must be disc-specific as well, to provide the mounting surface for the disc rotor.
In addition to increased stopping power, disc brakes provide the advantage of longer wheel life, because you don't have the brake pads rubbing on the rims. Also, if you should happen to hit a large pothole or other obstacle and severely bend your wheel, there's a better chance that you'll still be able to finish the ride and get home, since there's less of a chance the wobbly wheel will be cause the brake to rub. The only disadvantage of disc brakes is slighty increased weight compared to most rim brake calipers.
Disc brakes are available in "mechanical" or "hydraulic" versions. Mechanical disc brakes use the same housing and metal cable as standard rims brakes. Hydraulic brakes are a sealed fluid system; basically a miniature version of the same type of hydraulic brakes found on cars and motorcycles.
Disc brake pads are specific to the manufacturer and model of brake; there is no universal standard for disc brake pads.
U-brakes are common on BMX bikes. The attachment posts on the bike frame are similar to the posts used for cantilever and linear-pull brakes, except that they are positioned above the rim, rather than below. They use the same style of brake pads as cantilever and linear-pull brakes.
Side-pull brakes are sometimes found on low-end department store-level bikes and cheaper BMX bikes. They have a very simple single-pivot mechanism, and also can usually use the same type of brake pads as linear-pull or cantilever brakes.
Brake levers are designed to clamp onto either drop-style road bike handlebars, or onto upright mountain/hybrid handlebars. Additionally, brake levers are classified according to the amount of brake cable that moves when you squeeze the brake lever. Road calipers, cantilever, and BMX brakes all require "short-pull" brake levers. Linear-pull brakes require "long-pull" brake levers.
Most mechanical disc brakes use long-pull brake levers, but there are some versions that use short-pull brake levers, in order to be compatible with existing road brake levers. Hydraulic disc brakes, of course, are neither short-pull nor long-pull; the calipers and levers are sold as an integrated set.
Of course, the old-fashioned "pedal-backwards" brake can still be found on one-speed cruiser-style bikes, and some multi-speed bikes that use an internally-geared hub. This brake is referred to as a coaster brake. A coaster brake-equipped bike can be identified by an L-shaped steel bracket that is bolted to the bike's frame and the left side of the rear hub.
This article was first published on January 18, 2012.
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