Brakes are obviously the part of the bicycle that deserves the most attention. There are several different types:
* U brakes, named for their shape, are used on racing and most other road bicycles. There are various variants like centerpull brakes (Campagnolo Delta, an excellent brake but just too expensive), and sidepull brakes. The smaller they are the better they work because less material means less flex. There are cheap U brakes that would fit around your arm that you can watch bending when you brake. Good brakes are Shimano 105 and up, and any Campagnolo brake. Quick-releases help removing the wheel; Shimano integrates them into the brake and Campagnolo integrates them in the brake lever. You can ride Campagnolo levers with Shimano brakes but vice versa is difficult.
* Cantilever brakes are most often used on mountainbikes and hybrids whose tires are too fat to fit an U brake. I do not like cantilevers because they are hard to adjust and require continuous readjustment as the brake pads wear down. They tilt against the rim, which means that unlike U brake pads, cantilever pads do not touch the rim at a constant angle, so the angle must be readjusted frequently. Unfortunately, loosening the one single nut that secures the brake pad makes the whole assembly come loose and you have to adjust some six degrees of freedom all at once. Some people use spacers to adjust the pads while they press the spacers against the rim.
* Magura brakes replace cantilevers with two hydraulic cylinders that push the pads straight against the rim. Like regular cantilevers, they need a brake booster, a flat U-shaped piece of steel that connects both brake halves to keep them from pushing the fork apart. Maguras work really well; if they weren't so expensive I'd vote for throwing out all cantilevers.
* There are other forms, such as Shimano V brakes, but I have no experience with them. Hub brakes are often used on cheap bicycles; there are also high-quality hub and disc brakes that are useful for tandems which are much harder to stop. Hub and disc brakes have the disadvantage that they brake the hub, and a lot of force needs to be transmitted to the rim through the spokes.
There are a variety of brake pads that vary in softness. If the rubber compound is too hard, it doesn't brake well, especially in wet weather; if it is too soft, it wears down too quickly. Since rubber tends to get harder with time, brake pads should be replaced at least every couple of years. I prefer Campagnolo or Aztec. Some brake pads are longer than others, but I have not found this to make a difference. Some brake pads are designed for steel rims, but they don't make steel rims safe - never use steel rims because they are difficult or impossible to brake in wet weather. Good brake pads are not cheap, but this is about the worst place to save money!
Do not use ``safety levers'' that extend from the brake levers of cheap road bikes towards the stem (that holds the handlebars in the center). They aren't safe because they flex and brake poorly.
In road bike shift levers of the kind used for drop (racing) handlebars, the brake cables connect to the inside of the handle and run along the handlebars under the handlebar tape. The older type where the brake cable connects to the upper tip and arc up and then back down to the brakes are dangerous because you can accidentally catch the cable with your gloves, especially if you have aero (triathlon) bars.
For tips on installing and adjusting brake levers, see the chapter on handlebars.
See also an article on "Gear & Shift Levers"
