Be sure you have the correct replacement brake pad! El Cheapo bikes may have different pad systems than those shown here.

At one time, I had to keep 6 different types on hand for our family bikes.

Release the brake cable by removing the cable drum (cantilever brakes) or popping the retaining clip off the cable housing (V-brakes)

Remove the old brake pad. Before doing so, note the position of the stem on the slot in the brake caliper. Also note where the slot falls among the ball-joint spacers on the stem of the brake. (One set of spacers is larger than the other. As the brake wore down, the spacers may have been exchanged.) If there's any tread or grooves left on the pad, note which way it points.

The brake pad is removed by turning the nut on the end of the threaded stem. Put the new pad in its place, being sure to note whether the pad has a specified direction for mounting. In general, if there are Vs in the pad, the V points toward the back of the bike -- the direction the wheel will be turning into it.

Use the wider ball-joint spacer on the pad side of the caliper if you want your calipers wider apart. If you like them close, put the wider spacers on the nut side of the caliper.

A solid-stem brake pad has a pusharm that is gripped from the side. The nut on the opposite side of the cantilever loosens or tightens the grip on the pusharm.

Dial the cable-length adjuster on the brake lever almost all the way back (leave about 1/8 inch). Reattach the retaining clip to the brake cable. If the cable was tightened to compensate for worn brake pads, you may need to let the cable out a half-inch or so at the attaching screw on the caliper.

Fine-tune the position of the pads. Each pad should be only about 1/8" from the rim, with the stem pointing perpendicular to the facing edge of the rim. Partially tighten. Now toe the brake pad. This means the FRONT end of the brake pad will be a trace closer to the rim than the back end. Put a couple of business cards under the back end of the pad, then grip the brake lever to tighten the pad down against the rim. Now tighten the stem fully. Do this for each side.

If one caliper rebounds further away from the rim than another, or if one pad is rubbing the rim, adjust the spring tension on the calipers. Turn only 1/4 turn at a time, gripping the brake lever after each adjustment, then spinning the wheel to check alignment of the pads. You need to increase the spring tension on a pad that rubs (by turning the screw IN), so it rebounds further away from the rim. If the distance between rim and pad varies significantly as the tire rotates, you need to true the rim .

If necessary, make a final adjustment of the cable length using the adjuster at the brake lever. This determines the amount of "pull" you make on the brake lever before the brakes engage. Leave about one and a half inches of daylight between the brake lever and the handlebar when you're gripping the brake lever hard. (Some riders like the brake action closer to the handlebar. If so, you can back the cable tension off, but be certain there's at least 1/2" space between lever and handle bar when the brake is gripped as hard as possible.) For further information on brake tuneup s, see that section.

Follow the instructions above for release of the brake cable. Locate the retaining pin at the top of the brake cartridge. Grasp it firmly with needle-nose pliers, then pull it gently out. DON'T break it or lose it.

Slide the brake pad out at the open end. Use a small wire to clean dirt out of the front end of the cartridge. Now slide the new brake pad in. Push a bit, so the hole in the pad matches the hole in the cartridge. Re-insert the retaining pin, making certain it seats correctly. Follow the procedure above for adjustment of the brake clearance, toeing, and tension after pad replacement.