Bicycle brakes come in various forms, in part according to the intended use, and the various types are covered below. At the end of this article there’s a section on which type is recommended for each cycling purpose.
Rim Brakes
Rim braking is applied though friction blocks mounted in metal shoes normally acting upon the rim side walls. Sometimes the shoes can have new blocks inserted but with some the two are moulded together and the whole shoe is changed. The advantages of rim brakes are simplicity, low cost and low weight. The major disadvantages of rim brakes are that they are quite high maintenance through regular adjustment needs and they wear the rim walls necessitating rim replacement from time to time. The five rim brake types are listed below:
V brakes: These are the most common, being simple, cheap to make and effective. They consist of a pair of arms on the sides of the wheel rim area, pivoted on the forks or frame at the lower end and with brake shoes and blocks aligned with the rim side walls. The upper ends of the arms are joined above the wheel by a transverse cable which operates the brake by squeezing the arms together with a direct pull.
Caliper brakes: In their simplest form these have two curved arms centrally pivoted together at the fork or frame head and forming a horseshoe shape over the wheel perimeter. Brake shoes and blocks are mounted on the lower end of the arms alongside the rim walls. The upper ends of the two arms are extended beyond the pivot and a cable joining the upper extensions operates the brake by squeezing the arms together in a scissor action. They can have side or centre pull upper arms. On many of the better ones a refinement is having a dual pivot arrangement on a centre mounted backplate to give greater mechanical advantage to the cable action. There are several variants on caliper design for various operating action benefits
Cantilever brakes: These consist of two roughly L shaped arms either side of the wheel. Essentially similar to V brake arms in that they are pivoted at the lower end and have similar brake shoe mounting, the difference is the outward turn of the arms to form their inverted L shapes. On those outer ends of the upper arms are two short inner cable runs forming a roughly 90 degree inverted V to a centre point clamp above the wheel. A single cable run upwards from that centre point applies the pull, which by narrowing the V applies a closing force onto the brake arms as they pivot inwards. This is as simple as a rim brake can get.
U brakes: These are a form of cantilever and are specific to BMX bikes. They have a pair of side arms, each with a centre pivot, which cross over at the top. The top of the arms is pulled together by a cantilever cable pulling upwards to squeeze together the brake shoes below the arm pivots in a scissor action.
Hydraulic Rim brakes: The operation of these rim brakes by hydraulic fluid means some differences in the brake structure. One type has a pair of centre pivoted arms sitting at the sides of the wheel perimeter, each arm having a brake shoe at the lower end. A hydraulic piston between the upper ends of the arms expands them, which in turn pinches together the arms below the pivots to exert the braking force. A second type has hydraulic pistons fork or frame mounted at each side of the rim, each with a brake shoe directly mounted on it. Thus the hydraulic pistons act directly on the rim. The hydraulic fluid is delivered from master cylinders with integral reservoirs mounted as part of the brake levers. The fluid reservoirs can sometimes need to be topped up as brake friction pad wear takes place. The major advantages of hydraulic operation are the smooth and powerful transmission of braking effort and lower maintenance requirements since they are often self adjusting for wear. The sole disadvantage of any consequence is the higher cost.
Stirrup or Rod brakes: Of mainly historical interest but still seen at times on old bikes and in the third world, these consist of a stirrup sitting over the wheel with brake blocks that act on the underside of shallow V rims. Operated by pull rods above the stirrup, the lower ends on the stirrup are located on the forks or frame via short rods sliding in fork/frame mounts. Simple in construction and operation, these are the easiest brake type to make in the third world, needing only minimal facilities.
Disc brakes: These come in two main forms, cable or hydraulically operated, and are very similar to those on motor vehicles except for the disc being necessarily much thinner for weight saving reasons. They consist of a hub mounted disc with a disc edge caliper holding side braking pads which clamp onto the disc perimeter faces. There are two types of attachment for disk brake calipers. On one, the caliper attaches to an adapter, and the adapter fixes on to the disk mount tabs on the bike’s frame. These allow simple lateral adjustment of the caliper position. On the other type, the caliper attaches directly to the disk mount tabs and has to have shims added to laterally adjust the caliper. The mountings for both the discs and calipers have many variants, the IS types for both often ignored in favour of makers’ own systems.
Apart from laterally centralising the caliper over the disc, the brakes are adjusted by positioning the side friction pads as close to the disc as possible without touching the disc surface. Older calipers and some cable actuated calipers have one stationary pad and one moving pad. On these the stationary pad is first adjusted as close as possible before completing adjustment of the moving pad. Cable actuated calipers typically adjust the moving pad or pads by changing the length of the cable with barrel adjusters at the caliper or at the brake lever. Otherwise maintenance consists of renewing brake pads when worn. The best cable disc brakes perform satisfactorily, but many, particularly some cheaper ones, are not very effective.
Hydraulic disc brakes are far better than the cable operated ones, being smoother operating, more powerful and their friction pads often self adjusting, though some including many older ones have manual pad adjustment. Apart from that need on some, the only maintenance is friction pad renewal when worn and topping up the hydraulic fluid on some occasions. The fluid used has to be the correct one for the system, DOT4 or mineral oil, but the type is normally marked on the reservoirs. As with hydraulic rim brakes, the main downsides are the greater cost and weight.
Hub brakes: These come in various forms listed below:
Roller Brakes: This is a compact form which can also be integrated with gear hubs. They use a steel drum with three small steel braking shoes acting on the drum inner periphery and are actuated by three steel rollers being pushed onto inclined ramps. The rollers running up the ramps squeeze the steel shoes against the drum braking surface as the wheel and drum rotate. Normally operated by cable, the ramp action forms a servo mechanism, self applying braking force derived from the bike’s kinetic energy. The ramps and drum operate in a greased environment to prevent squealing. When used in higher load situations which could generate excess heat, an optional radially finned cooling disc is attached to the outer face of the drum. The main advantage is that they are very long term maintenance free, only needing an application of a special grease through the small hole provided if ever squealing or poor braking action arises. One disadvantage of roller brakes is that they do not have fast acting very strong braking, so they are usually seen on utility bikes which are mostly ridden at moderate speeds. Another disadvantage is that the servo action build up of braking doesn’t consistently reflect the strength of the rider’s brake application.
The Coaster brake is a variant of the roller brake only in respect of the way it is applied. These are only on rear wheels and are applied by back pedalling, so are a rear wheel foot brake. A freewheel is incorporated so that pedalling can still be stopped, the braking action only occurring when back pedalling. These are popular in some of the northern European markets but rarely seen or liked elsewhere.
Drum brakes: Not often seen now, these are miniature versions of the drum brakes once universal on motor vehicles. Like those, they have a drum with two internal shoes fitted with friction linings which are expanded onto the inner drum periphery by the brake application. Any oil or grease leakage from the wheel hub bearings onto the brake linings impairs the braking efficiency, and this together with lining wear and roller brake availablity has caused their past popularity to largely vanish.
Band brakes: These consist of a steel drum mounted on the hub with a steel band wrapping around the outer drum surface. The band is anchored at one end and the other end pulled into contact with the drum by cable operation. The pulling end is chosen to give the band a self-wrapping action due to the wheel’s forward rotation. Not just cheap but very nasty, prone to horrific squealing when drying out and to be avoided. Thankfully they are rare now, just occasionally seen on the side of some low cost rear hub motors.
Electric brakes: These use a powerful magnetic field to limit or stop wheel rotation so have no wearing surfaces, a very big advantage. For obvious reasons these are usually integrated as part of a hub motor. These hub motors also regenerate energy from the braking which is returned to the e-bike’s battery, just as on hybrid cars. At present only seen in Japan on one e-bike front hub motor and bike from Panasonic, interest has been expressed by Derby Cycles in Germany who make the Kalkhoff and other well known e-bike brands. Hopefully the Panasonic design will be successful and popular, leading to electric brakes being introduced more widely on e-bikes for their major benefit.
Regenerative braking: This form of electric braking I’ve shown separately to reflect that it’s a by-product of some direct drive hub motors when regeneration is switched on. It provides some slowing of the bike useful to hold back speed gain such as on downhills, but in this form it’s not a full braking system.
Choosing a braking system
An important consideration is that brake levers are specific to each brake type due to their different movement characteristics. Avoid mixing the lever and brake types.
V brakes, also called direct-pull brakes, have long been dominant in the popular market due to their low cost and high performance, but disc brakes have made increasing inroads on most consumer bike types. However, each type is considered to have particular cycling applications which I’ve explained below:
Road racing and serious club sport riding purposes are almost always served by caliper brakes which provide best for all the various needs. As a side issue, the UCI doesn’t yet allow disc brakes in race cycling due to various unresolved technical and safety questions that they have in respect to racing’s special needs.
General all-purpose bikes are well suited by either V or disc brakes, which type chosen being according to budget and personal preferences regarding maintenance needs and their image. Discs are widely thought to have a better personal image.
Utility bikes generally used at moderate speeds can use any brake type but are particularly suited to roller brakes for their maintenance free character and external cleanliness. However, very heavy riders in extremely hilly areas can push these brakes close to their operating limit of 100 kilos per brake, especially if carrying additional loads in panniers or trailer towing. Even well short of the limits the braking weakness can become very apparent. For them, disc brakes are a good low maintenance option.
Mountain bikes and MTBs are well served by disc brakes, particularly if intended for occasional use in very muddy conditions since rim brakes can be seriously clogged up by mud accumulation. Otherwise V brakes are a low cost alternative.
BMX bikes used for street and trail riding mainly have U brakes, though for BMX racing V brakes are often preferred.
Cyclocross biking favours cantilever brakes for their ability to cope with mud quite well and their simplicity. A few riders now use V brakes instead but they are not a good option in muddy conditions. As a result of the recent lifting of the UCI ban on disc brakes in Cyclocross, they have increasingly appeared in manufacturers’ ranges, but now perversely the UCI are urging national committees to ban them again, mainly because of poor user take-up and a desire to return to the former simplicity.
Our thanks to Flecc for this article. Flecc is a long-time contributor to Pedelecs. If you have a question you’d like Flecc to answer please contact us here.
