page_title: Bicycle brake
section_title: Roller cam brakes
hierarchical_section_title: Bicycle brake / Brake types / Rim brakes / Types of rim brakes / Roller cam brakes
caption_attribution_description: Example of a front Roller Cam bicycle brake, cropped from original.
context_page_description: A bicycle brake reduces the speed of a bicycle or prevents it from moving. The three main types are: rim brakes, disc brakes, and drum brakes.
  Most bicycle brake systems consist of three main components: a mechanism for the rider to apply the brakes, such as brake levers or pedals; a mechanism for transmitting that signal, such as Bowden cables, hydraulic hoses, rods, or the bicycle chain; and the brake mechanism itself, a caliper or drum, to press two or more surfaces together in order to convert, via friction, kinetic energy of the bike and rider into thermal energy to be dissipated.
context_section_description: "Roller cam brakes" are centre-pull cantilever brakes actuated by the cable pulling a single two-sided sliding cam.  (First and second-class lever designs exist; first-class is most common and is described here.)  Each arm has a cam follower.  As the cam presses against the follower it forces the arms apart.  As the top of each arm moves outward, the brake shoe below the pivot is forced inward against the rim.
  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.  And they 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 of WTB around 1982 and licensed to Suntour.  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.
caption: Roller cam front brake.
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