Cantilever Brakes

If you have a touring bike, cyclocross bike, or an old mountain bike you probably have cantilever brakes. These can be tricky to install, but they're very powerful once properly set up. A common problem is the pad position. If the pads are installed too close to the brake arm, they typically give weak brake performance. Similarly, if the straddle wire is too long then the performance suffers as well. Ideally the pads should stick out as far as possible from the brake arms, and the straddle wire should be as low as possible without touching the tire. This is an example of a good setup:

To change or adjust the pads, hold brake arm in place with an allen wrench while unscrewing the nut on the opposite side with the right size wrench (adjustables don't work well here, use a box end wrench):

This will loosen up the clamp holding the pad in place, and you can now move it around or swap the pad out for a new one. Position the pad so that it lines up with the curve of the rim, and hits the rim squarely rather than on a sharp angle. You also want to angle the pads inward slightly to keep the pads from squealing, and to give the brake a softer feel.

Finally, hold the allen wrench in place while tightening the nut to lock in the pad's adjustment. Pull the brake lever and check to see where the pads meet the rim. The pads should be aligned with the rim, and the shouldn't drag when the brake lever is released. If one side is dragging, then use the spring tension adjustment screw to center the brake arms:

Turning this screw in will pull the brake arm away from the rim, while loosening it will move the brake closer to the rim. You want the brake pads to sit the same distance away from the rim, so adjust this screw accordingly. If the brakes are centered, slightly toed in, and have a strong feel then you're done.