In stating the obvious, brakes use friction to convert kinetic energy into friction and heat, slowing it down. While stopping is the main function of brakes, they can also be used in steering the bike by sliding the back-wheel out or dragging it in- line, or even negotiating tight offroad corners with the front brake.

Disc brakes operate at lower speeds than rim brakes, which allows for more consistent braking at high speed. (A brake, which performs well at speed, may feel grabby at low speed; a brake which feels ‘just right’ at low speed, might lack power as speed increase.)

Having said that, there are basically 4 types of bicycling brakes currently available, being a coaster, calliper, cantilever or disc brake.

Coaster brakes

A coaster brake combines a rear, freewheeling hub with a brake, operated by pedalling backward. It is perhaps the best brake type for little children’s bicycles, as their physical hand-strength might not have properly developed. A coaster brake also permits the bicycle to be ‘rolled backward’ without causing the cranks to turn, which is useful in some freestyle tricks.

Calliper brakes

These are the conventional road-bike brakes, although low-end mountain bikes are also fitted with them. They consist of a cable-actuated scissor-like leverage system that forces rubber pads onto either side of the wheel's rim. These are generally the lightest brakes and are competent, but are not considered powerful.

Side-pull brake - A brake where both cable arms are on the same side of the calliper, one being pulled by the inner cable, the other being pushed by the cable housing. Single-pivot side-pull brakes have both arms pivoted on a central point, usually the same bolt that holds the calliper unit to the frame of fork. Dual-pivot side-pull brakes have a separate pivot for each arm. Dual-pivot brakes usually have more mechanical advantage than single-pivot units, but they don't track out-of-true or irregular rims as smoothly as single-pivot units. V-brakes are technically side-pull designs also, but this term is not normally used for them, since they are a type of cantilever, not calliper brake.

SLR- An acronym for 'Shimano Linear Response' braking systems which feature a series of friction-reducing modifications introduced in Shimano’s late 1980's '105 group'. The 105 SLR brakes (perhaps the best side pull callipers ever made) incorporated ball bearing calliper pivots, low-friction cables, nylon spring bumpers and reduced spring tension. By adding a weak return spring to the brake lever, they were able to drastically reduce the tension of the calliper return spring. Since the cable was being pushed at one end and pulled at the other, a positive return function could be attained with a much lower overall spring tension. This greatly improved the "feel" and sensitivity of the brake. (This aspect of the SLR design was, perhaps, copied from Dia Compe, which calls it "B.R.S.".) “Super SLR” - which is Shimano’s name for double-pivot brakes - replaced this system.

Cantilever brakes

Levers are attached to the fork/frame (on either side of the rim) being joined at their tops by a crossover / straddle cable / transverse cable. Pads that align with the rim are attached to the arms, and a further cable from the brake lever is attached to the centre of crossover cable. When the brake lever is pulled, the 'cantilevers' are drawn together forcing the pads onto the rim. These brakes provide better mechanical advantage than calliper brakes, but they are generally considered inadequate as the mechanical advantage decreases towards the end of the pull. They are also rather difficult to adjust and offer limited clearance over the tyre.

V-brake - This brake - originally a Shimano trademark - is a direct pull cantilever brake that does not use a separate transverse cable. It has two tall arms attached to the frame - one of which has a housing stop and the other an anchor bolt - on either side of the rim sporting rim aligned pads. The cable runs horizontally from one arm to the other, delivering more mechanical advantage than normal cantilever brakes - which advantage even increases during pull - and they require 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 that maintains the shoe at the 'correct angle' as it approaches the rim. V-brakes feature increased clearance over tyres (over other cantilever brakes), but their power drops off in the wet - especially with mud – and they do not function well on buckled rims. Overall V-Brakes offer unrivalled value for money (for general application).

U-brake - A form of cantilever brake that works like a centre pull calliper wherein the "L" shaped arms cross over above the tyre, 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 it - as with conventional cantilevers. They use the same type and placement of studs as roller cam brakes do, but are difficult to set up and ‘get to’ due to their awkward positioning.

Hydraulic rim brake - A rare brake find, with hydraulic pistons attached to the frame/fork on either side of the wheel (in the same place as the levers for V-brakes) that push pads onto the rims. A hydraulic tube replaces the cable from the brake lever to the pistons. There are two types of pad and rim: standard and ceramic. Ceramic are very expensive, last longer, and offer greater stopping power, but if they become oiled, both rim and pads must be replaced. Using ceramic rims and standard pads will give you good performance until the pads wear down. They are very sensitive to set-up, can be knocked out of alignment, but are slightly more powerful than V-Brakes in the dry.

Roller cam-brake - A type of brake which uses a triangular cam with seesaw like arms, pivoted in the middle on cantilever-type studs. The cable -being attached to the narrow end - pulls the cam with its sloping sides pushing outward on rollers attached to the upper end of the brake arms. Roller-cam brakes permit the use of variable ratios (the sides of the cam curve) to make the pads travel in toward the rim fast, slowing them down as they engage. This gives more mechanical advantage in the actual braking range while allowing the shoes to back off farther from the rim. Roller cams have the advantage of not protruding past the sides of the frame, which made them popular when there was a fad for placing the rear brake under the chainstays.

Self-energizing brakes - Self-energizing brakes use some of the braking force to provide a "power assist" to the brakes. The best-known self-energizing brake is the Scott-Peterson (Sun Tour) cantilever, which has a steep helical thread as its pivot, so that the forward force exerted by the rim against the pads helps cause the pads to press harder than they would from hand effort alone. Self-energizing brakes are quite controversial, because they can have a non-linear response that leads to an unplanned wheel lock-up.

Disc brakes

A hub - based disc brake - similar to an automotive disc brake - consists of a disc that bolts on to the wheel’s hub and a calliper attached to the frame / fork pinching the disc. Some early disc brakes had a reliability problem in that outer part of the disc could break away from the part that attached to the hub (causing complete failure without any warning). Disc brakes can dissipate heat better and are a bit less prone to collect mud (are less affected even when they do become soiled) which makes them popular in off-road application. Disc brakes cause no damage to rims, are unaffected by rim buckling, offer better heat dissipation and can have very powerful stopping-power, the flip-side being their cost, maintenance and a bit of added weight.

Mechanical disc brakes - Mechanical systems are a bit lighter and cheaper than a hydraulic disc braking systems, can be adjusted and serviced more easily, but cables bedding into the housings (so called “cable stretch”) make them less responsive over time, and the lack of hydraulic advantage make them 3rd prize. As they constitute relative 'new development' they sometimes have a poor reputation with many inferior systems being found.

Hydraulic disc brakes - Hydraulic discs are standard on all high-end mtbikes. The weight penalties associated with discs have been largely overcome, and they constitute the most powerful bicycle brakes available. Some manufacturers use a mineral oil base - which does not absorb air or water - rather than the DOT brake fluid – which doesn’t really affect performance, but mineral based brakes do not need to be bled to have pollutants removed (unless the tube is punctured), while other oils must be bled relatively often, at some effort.

Brake cables do seem to ‘stretch’ when applied as the housings compress under tension. It results in a ‘mushy’ feeling, especially when using large levers. Hydraulic lines – similarly - swell and expand under fluid pressure having the same effect. On both cable and hydraulic brakes there is always a slight difference in feel between front and back brakes, the front feeling crisper.

Friction exists in all systems, but the major difference is that a cable’s mechanical friction increases with normal force and hydraulic friction increases with velocity.

On a mechanical disc the friction in the cable is greatest when you have the most force on the lever, where fine control gets hard to find. On a hydraulic system the most friction is found when the lever is moving (but before braking has begun), yet when maximum force is applied the fluid is no longer moving, and friction drops to zero. Accordingly, hydraulic systems have fine control at or near maximum power, and its power, feel and control cannot be matched.

In SA we basically use calliper brakes on-road, V-brake and hydraulic disc brakes off-road, and there are several manufacturers of brake systems commercially available. Consider your requirements and your budget, but make sure you know how to maintain your brakes (inspect them regularly) and how to use them! Brakes are an all-important safety issue, and should never be overlooked!