Figure 1 - A common side pull calliper brake
The most inexpensive (and least effective) type of bicycle brake is the side pull caliper brake shown in Figure 1. This brake is as simple as it looks – just a pair of steel arms that act like pliers in order to push a pair of rubber pads onto the edge of the rim to creates braking friction. This type of brake has been around since the wooden wheel bicycle, and they are very easy to install and adapt to practically any cycle that has a standard rim.
The downside to this style of brake is that it offers barely enough stopping power to lock up a wheel, and when wet becomes practically useless. I sometimes use this style of brake as a front brake when I have a much better braking system on the rear such as a disc brake. I would not rely on this type of brake if it was the only brake on a cycle.
Figure 2 - Cantilever brakes on a front fork
A much better (and more modern) variant of the pad brake is the cantilever or “linear pull” brake shown on the front fork in Figure 2. Because of the way the cable force is applied to the arms, the leverage is so much better than the side pull brake, making these brakes highly effective. This style of bicycle brake is just as good as a disc brake, and is very easy to install and setup.
The cantilever brake does require a pair of cantilever “studs” be mounted to the frame in the proper position, but this is not difficult to do, as the studs can be cut from one frame and welded to another frame. These brakes suffer a bit of wet rim weakness as well, but will still have enough power to lock up a wheel even in the rain.
Figure 3 - Disc brake rotor and calliper
A disc brake is currently the ultimate option for braking power and smoothness on a bicycle, and because of its widespread use, disc brakes are affordable for the garage hacker. A disc brake has a caliper system that presses two brake pads onto a disc rotor (Figure 3) to create braking friction. Disc brakes have more than enough stopping power for even large cargo bikes, and are easily adapted to trikes and quads since the rotor can be mounted to an axle.
Disc brakes have smooth operation through their entire range, and are only slightly impaired by water, so they are also great for all weather use. Installation of a disc brake is slightly more involved than a pad brake, but the ability to adapt them to an axle makes them the best solution for delta trikes and quadcycles. A single disc brake is more than enough for a large cargo bike, although having two brakes is always preferred.
Figure 4 - A standard bicycle brake lever