A bicycle must perform three basic functions, namely:
Virtually all bikes perform these functions in essentially the same manner. Pedals, chains, and gears allow force to be applied to the rear wheel. The front wheel can be turned relative to the rear one to influence direction. And brakes use friction to convert the bike’s kinetic energy into heat, slowing the bike down (or, at least, making it go less rapidly than it would otherwise have gone!) It is useful to remember that, while stopping is the main function of brakes, they can be extremely useful in steering as well, from sliding your back wheel out, or dragging it back in line, to turning extremely tight corners on your front wheel!
These are the conventional road-bike brakes, although some very low-end “mountain bikes” are still fitted with them. They consist of a scissors-like leverage system that forces rubber pads onto either side of the wheel’s rim. A cable from the brake lever draws the “handle” end of the “scissors” together, forcing the “blades” together, and hence the pads onto the rim.
These are generally the lightest brakes, but only provide enough braking power for road use, and even then I often wish for more!
Recommendation: If you have these, either sell your car to afford new brakes, or make sure your will is up to date.
Here, a lever is attached to the frame on either side of the wheel. The top of the levers are joined by a piece of cable, and pads are attached part way down so that they align with the rim. The cable from the brake lever is attached to the mid-point of the cable joining the cantilevers. When the brake lever is pulled, this results in the cantilevers being drawn together, forcing the pads onto the rim.
Although this provides better mechanical advantage than calliper brakes, and you may even be able to lock-up your rear wheel, these are still generally considered inadequate for sport- or competition-level off-road cycling. A key short-coming is that the mechanical advantage decreases towards the end of the pull, meaning that you must apply more force with your hand. Further, they are difficult to adjust, and offer limited clearance over the tyre.
Recommendation: unless you are completely broke, or have a serious masochistic streak, upgrade!
These are the standard on low- to mid-range mountain bikes, and are even found on many upper-end models. Virtually all mountain bikes, except for a few very-top- and very-bottom-end models, can be fitted with these brakes, even if they don’t come standard.
These are similar to cantilever brakes, in that they have a lever attached to the frame on either side of the wheel, and pads part way up the levers. However, the cable from the brake lever runs between the tops of the levers. This produces a greater mechanical advantage, which actually increases slightly during the pull, and provides greater clearance over the tyres.
These are the simplest, lightest brakes that provide the stopping power required for XC mountain biking, or AR. It is perfectly possible to lock up the rear wheel on any surface, though it is almost impossible to lock the front wheel when traction is good. There are two main disadvantages to these brakes: their power drops off greatly in the wet, especially when mud is involved; and they do not function well on rims that are buckled to any significant degree. The significance of these issues depends on the nature of the course involved (muddy, rocky, etc) and the preferences of the rider involved.
If you find that your V-brakes are lacking power, check that the pads are reasonably new and clean, and that they are set up correctly. Worn pads, or those polluted with oil must be replaced – it is not possible to clean oil off, as it is absorbed deep into the pads. The correct set-up is described in a separate section at the end of this article.
There are two types of pad and rim: standard, and ceramic. Ceramic are very expensive, last longer, and offer greater stopping power. If they become oiled, both rim and pads must be replaced. This limits their use to sponsored pro-elite XC racing. Using ceramic rims and standard pads will give you good performance, for a very short time until the pads are worn down. Do NOT go for ceramic options!!
Recommendation: V-brakes are adequate, unless you are doing downhill or trials work as well. Heavier riders may appreciate greater stopping power, but will be able to make do.
Hydraulic rim brakes
These are something of a rarity. Hydraulic pistons attach to the frame on either side of the wheel, in the same place as the levers for V-brakes, and push pads straight onto the rims. The cable from the brake lever is replaced by an hydraulic tube.
The stopping power offered in the dry by these brakes is second to none, including disc brakes. Magura (www.magura.com) make the only examples I have seen, but they are impressive enough to have become essential equipment for trials-riders, as well as finding favour with some endurance riders. At a recent trials competition in the UK, I counted less than half the beginners without Maguras; all higher-classed riders used these impressive brakes.
I received a set of Magura rim-brakes from Team Lemming in the UK to try out, but found them too finicky to be useful for AR. No matter how I tightened the bolts, every time I removed my wheels, the pistons would be knocked out of alignment, and I would have to spend ten to twenty minutes realigning them before riding again. Other riders, on the other hand, assure me that they have had no such problems.
They have the same sensitivity to mud and wet that all other types of rim-brakes have, and are even less tolerant of buckled rims – you have at most 5-7mm of clearance on either side of the rim. If your wheel buckles, you will have to completely remove the brakes from the affected wheel, and tie them up somewhere.
Recommendation: If you have them, and they work for you, stay with them. If you want to get serious about trials, put them on your trials bike. However, if you are looking for new brakes for AR or XC, your money would be better spent on discs, or even V-brakes and a couple beers.
Disc-brakes are the high-performance animals of the braking world. They have replaced all other types of brakes on both motor cars and motor bikes, with the exception of only a few bottom-end models. Looking at the offerings from the major mountain bike manufacturers over the past few years, it is likely that we will see disc brakes becoming standard on mid- to upper-end XC bikes, and maybe even lower-end bikes.
These brakes use a metal disc attached to a purpose-build hub, and pads press onto the disc. The frame and forks of the bike must be designed specially to accept disc brakes. Compatible bikes will have two holes near the bottom of the frame or forks on the left hand side, onto which the brake pad housing can be bolted. With the exception of some of the Manitou forks, these holes are horizontal and perpendicular to the plane of the bike.
The main advantages of disc brakes, from an AR perspective, are that they are generally clear of mud, are less sensitive to mud even when they do become spoiled, and are completely unaffected by rim buckling. The flip-side is that, should you buckle the disc, you must remove the pad housing completely. Other advantages include better heat dissipation, and extremely good stopping-power (I have frequently locked my front wheel), but these are of less importance in AR.
There are two types of disc brakes – mechanical (cable links the brake lever to the pads), and hydraulic (hydraulic tubing transfers the pressure.)
Mechanical systems are a bit lighter and cheaper than hydraulic systems; they can also be adjusted and serviced more easily. However, they have only recently been developed to the point where they deliver reasonable performance, and so still have a poor reputation, and many inferior systems can still be found. Further, cable-stretch and friction within the housing makes them less responsive and powerful than hydraulic systems.
Hydraulic discs are de rigueur on all downhill machines, and most top-end XC bikes. The weight penalties and rubbing associated with discs in years past have largely been over-come, and they are now well-suited to XC and AR. The best brakes are made by Hayes, Formula, and Magura, with Hayes and Formula concentrating on the downhill market (heavy brakes focused on heat dissipation rather than smooth running), while Magura has virtually cornered the XC market.
One extremely important difference between Maguras and other manufacturers is that Magura uses a mineral oil which does not absorb any air or water, rather than the DOT brake fluid used by the other manufacturers. While this does not affect performance, it means that Magura brakes do not need to be bled (have pollutants, such as air or water, removed) at all in the first five years of heavy use, unless the tube is punctured, while the other makes must be bled relatively often, at considerable effort. Indeed, the Magura warranty is void if the brakes have been bled by a non-authorised service centre.
Recommendation: While these are not the be-all and end-all of brakes, they are beautiful tools that will improve performance in high-pressure situations. They do, however, demand a bit more care than V-brakes.
This table compares the pros and cons of the various systems from the perspective of AR, which is largely the same as XC racing and endurance events. Retail prices supplied by Cycle Logic, Randburg. [Note this article was written in the early 2000’s]
|Calliper||None||Stopping power||Why bother?||Avoid like the plague!|
|Cantilever||None worth mentioning||Limited stopping power, difficult to set up||Why bother?||Avoid like office gossip!|
|V-brake||Good stopping power, easily maintainable, cheap||Becomes fouled with mud, and intolerant to buckled rims||Shimano Deore: R600||Perfectly adequate, if set-up correctly|
|Hydraulic Brake Rim||Excellent stopping power and control||Hard to set up correctly, easily knocked out of alignment, easily fouled by mud, and even less tolerant to buckled rims||Magura: R1,300 – R2,200||Too finicky for the rough-and-tumble of AR|
|Mechanical Disc||Good stopping power, easily maintainable, reasonable control, not sensitive to mud or buckled rims||Still young and relatively unproven technology; discs may be damaged; potential for rubbing||Formula: R400; Shimano Deore: R1,000||Not bad|
|Hydraulic Disc||Excellent stopping power and control, not sensitive to mud or buckled rims; good enough for some DH, even!||Most makes require extensive maintenance, discs can become damaged, expensive||Magura: R2,000 to R3,000; Formula: R4,000; Shimano Deore: R1,599||Not bad|
Correct setup for V-brakes
These steps will give you a good balance of stopping power, rim clearance, and robustness of set-up. Required tools: 5mm Allen key.
- Ensure that your pads are reasonably new, have not been worn unevenly due to incorrect alignment, and are clean (oil-fouled pads must be replaced)
- Ensure that your rim is true (not buckled). If it is, true it yourself, or take it to a bike shop
- Ensure that the pads are on the correct way around (their curved side must curve in the same direction as the wheel – duh!)
- Loosen the pads on both sides of the rim, and gently squeeze the levers together until the pads are touching the rim
- Check that the pads are touching in the middle of the rim, rather than the inner or outer edge; too far in, and they may slip off the rim, too far out, and they will wear through the tyre
- Ensure that the pads are lying flat against the rim; the old trick of putting the pads “toe-out” to ensure even contact pressure is no longer needed
- Tighten the pads, being careful not to harm the alignment
- The brake cable can be removed from the one lever of the brake by hand, allowing the levers to move apart for removal of the wheel. Set the cable “on-edge” here, so that the levers are a bit closer than they would usually be. Adjust the brake cable so that the pads are just touching the rims. When you position the cable correctly, you will have the correct clearance. Note that this only works if your rims are reasonably true!
- Adjust the small screws on either lever to ensure the pads have equal clearance from the rim. Screwing one of them out reduces the clearance on that side, while screwing it in increases the clearance. If this does not provide sufficient adjustment, unhook the spring from behind the lever with inadequate clearance, and bend it outwards before replacing it (this also helps with levers that are reluctant to return to their position)
- Check that the brakes are functioning properly, first by pulling the levers and observing how and where the pads seat on the rims, and what position they return to, and then by going out for a ride, and braking in a variety of situations. You may have to tweak the adjustments several times before you get the perfect setup
It is important to frequently clean and lubricate your cables. Do this by unhooking the cable-housings from their guides, and cleaning the cable, section by section, by drowning it in chain lubricant and rubbing vigorously with a cloth. When you return the housings to their positions, try to fill them as much as possible with lubricant. Replace them when they become damaged or worn.
There are several brake systems available that are more than adequate for the demands of AR, XC, and endurance racing. Look at what you want to do with your bike, look at your bank balance, and go forth!
While you’re at it, make sure you know how to maintain and tune your brakes, inspect them regularly, and learn how to use them. Brakes are an important safety issue, and should not be over-looked.
Author: Dylan Morgan