The most efficient system on your bike is the one that is most often overlooked. For the amount of effort you put into a simple brake lever the result is really quite amazing. You can stop a bike from 40 miles per hour in a surprisingly short period of time by squeezing a simple lever relatively gently - compare that to the amount of effort needed to get the bike from standstill to 40mph in the first place. That gives you some idea of how mechanically efficient braking systems are. But the main principle of a braking system, no matter how they work is very simple.
A rotating wheel on a bike contains a certain amount of kinetic energy, and a brake just converts this energy into heat energy. This heat energy is then dissipated through components and also into the atmosphere. This can be done several ways, the most common one being a simple lever system that pushes two rubber based blocks against the wheel of the rim. Another option is to make a disc and attach it to the wheel, and then push pads against the disc.
Or you can make a drum section inside the hub, and use shoes that expand outwards and push against the inside of the drum. Those are the most common brakes, and there's always the good old 'foot jammed against the wheel' approach I'm sure we all remember from being young and owning a bike with no, or broken, brakes on it. The only trouble there is the heat goes into your trainers, and the sole of your shoe is rarely much of a match for a spinning tyre, so it ends up being somewhat sacrificial and uncomfortable.
Know your brakes - The different systems and how they work...
Cantilever brakes use a straddle wire which, when pulled, draws the cantilever arms together. They can be tricky to set-up and require careful tow-in to prevent squealing. Used mostly on light touring bikes and older Mtb's and are compatible with drop bar levers including most STI and Ergopower controls.
This is the generic name that was invented by Shimano -SRAM call it Linear-pull but they're essentially the same. The brake arms are longer than those of a cantilever brake, giving a far greater leverage ratio. As disc brake systems become ever lighter V-Brakes are increasingly being phased out on Mtb's but they are still seen on budget spec bikes and on straight handlebar touring bikes - they are a more powerful alternative to cantilevers.
These were originally conceived for BMXers and have shorter actuating arms than full V-brakes. These brakes are compatible with all bikes fitted with drop handlebars and Shimano STI and Campagnolo Ergopower levers.
Seen less and less these days the V-Daptor alters the amount of cable 'pull' and must be fitted where V-brakes are used with either Campagnolo Ergopower or Shimano STI controls.
Not seen on light road bikes, they are appearing more on commuter bikes and tourers thanks to increasingly lower costs. The advantages are superior power and because it's operating on a hub mounted steel rotor instead of the wheel rim it doesn't kick up messy aluminium oxide deposits from the rim in wet weather. N.B. you'll need calliper mount braze ons (see a frame builder) and a rotor specific hub (front, rear or both).
It's a pad thing
The standard brake blocks on some brakes are, well, rubbish. There's a lot to be said for splashing out a little cash for some aftermarket pads, and this is nowhere more evident than in the rain. There's always going to be a delay between the pads hitting the rim and starting to generate braking force as they have to clear the water from the rim and start converting that kinetic energy into heat. But some pads are just more consistent in the rain, and it's this consistency without nasty surprises that really shows the difference between a good pad and a lesser and often cheaper one. Brakes are your safety, so spend wisely...
Not all disc brake systems run automotive hydraulic brake fluid. Some systems, such as Magura and Shimano, use a mineral based fluid. So despite what you might hear from friends or ill-informed forum monkeys, you cannot just "bung some DOT 5.1" in there and get your brakes working again. Do that with a system designed for mineral fluid and you'll be replacing every single seal within two days - and a system designed for DOT 5.1 or DOT 4 will give you about a week if you fill it with mineral fluid. Read the instructions carefully when you get your brake, or it could end up expensive.
There's plenty of debate about what brakes are best for touring, and some of it makes sense (usually from people who actually tour ...) and some of it is people vainly trying to regurgitate bicycle science text books. So does a touring bike need disc brakes? And should they be hydraulic? There is no clear cut answer to be honest, but disc brakes can be more consistent, and can be more controllable on long descents when you have a bike loaded up with long distance kit. But if you snag a hose or cook the brake fluid then are you going to be carrying some with you? And a bleeding kit? Hmmm... Cable operated discs have a lot going for them in this respect, but are they better than a top quality rim brake?
Really it comes down to you either having a bike with disc mounts, or you will have to get them added afterwards. The adding afterwards option is perfectly viable, but bear in mind that lightweight touring forks should not have disc brake mounts added to them. Likewise at the lighter end of the frame weight scale you will be looking at a brace between seat and chainstays to do the job even half properly if you want a disc on the rear. Also, depending upon your front pannier system you might need to shuffle the lower mounting outwards by the use of a spacer and longer bolt.
Worth a Look
Our favourite lever for time trialists is the ever effective Dia-Compe 188, while we'd certainly go for the Cane Creek Crosstop for tourists, 'crossers and commuters.
Moving on to callipers, the Dia-Compe 806 long reach brakes are perfect if you're pressing an old bike back into service as a road fixer. Top performers among the normal reach brakes are the Guess callipers, though they may require adjustment of the pivot bearings. Again, they can also be upgraded easily by fitting better brake blocks. Among the more expensive offerings, the standard of materials and finish goes a long way to justifying the cost of the Mavic SSC callipers.
For serious performance on a tourer or mountain bike the Avid Juicy 5 is a well established favourite, but if you're on a tighter budget then the Shimano Deore M495 disc provides stopping power that far surpasses that of cantilevers or V-brakes.