The caliper of a brake is the mechanism that pinches the pads inward against the wheel rim. In most cases, a road bike caliper is a sidepull device that bolts on through a hole in the brake bridge or fork crown. Dual-pivot sidepull brakes mounted on a center bolt have become the industry standard. They are powerful and easy to keep in adjustment. Follow these steps to install and adjust front and rear brakes.
Installation. Stick the center bolt through the hole in the brake bridge or fork crown and tighten it in place with a 5mm hex (or Torx T25) key inserted into the recessed nut. Get a longer recessed brake nut if needed to ensure at least six turns of engagement (this is only an issue on the fork).
Cable hookup. Open the quick-release on the caliper (or on the lever on Campagnolo and some Mavic) before you connect the cable. Route the cable housing into the barrel adjuster on the brake arm. On the end of the housing, install a ferrule if one will fit into the barrel adjuster. Push the cable through the housing and the barrel adjuster and under the cable-fixing-bolt washer on the lower brake arm. Pull the cable taut and tighten the bolt with a hex key.Close the quick-release after the cable is connected.
Centering. You are trying to achieve an equal amount of space between the pad and the rim on each side. The simplest and quickest way to center these brakes requires no tools. Just grab the brake and twist the entire thing into position (don’t mess with the mounting bolt; leave it tight). But do make sure before riding that the recessed nut on the back of the brake bridge or fork is tight.
The centering method built in by Campagnolo, SRAM, and Shimano consists of a setscrew. The setscrew is on the side opposite the cable. On Campagnolo, it is on the arm, just above the pad, and it takes a 2mm hex key. On Shimano and SRAM, the setscrew is on the upper end of the taller brake arm.
As you tighten the screw, the pad on that side moves away from the rim. Loosen the screw, and the other pad (the one on the cable side) moves away from the rim. SRAM and Mavic dual-pivot sidepull brakes require working a 5mm hex key in the recessed mounting nut while rotating the nut behind the brake caliper with a 12mm or 14mm cone wrench, respectively (similar to center-pivot centering).
Pad adjustment. Loosen the pad-mounting bolt with a hex key (generally 4mm or 5mm). Slide the pad up or down along the slot in the arm to get the pad even with the height of the rim’s braking surface. Twist the pad in the vertical plane to have the top edge of the pad follow the curve of the top edge of the rim. While squeezing the brake lever to hold the pad against the rim, tighten the pad-mounting bolt. Make sure the pad does not twist as you tighten (if it does, hold it with your fingers as you cinch the bolt). Also make sure that the pad does not contact the tire, which could quickly wear through the tire sidewall, causing a blowout. Higher-end brakes also have an orbital adjustment of the pads to align the face of the pad flat or toed in against the rim by means of a concave washer that nests against the convex face of the pad holder. If the brake squeals or is grabby, toe the pads in a bit so that the forward end of the pad is a little closer to the rim than the rearward end.
Spring-tension adjustment. Campagnolo, SRAM, and some Shimano dual-pivot brakes have a setscrew that pushes on the end of the return spring. It is located on the arm, above the cable-side pad. If you tighten this screw (with a 2mm hex key), you will also tighten the spring, thus making the brake both harder to pull and quicker to snap back.
Pad replacement. When the pads wear to the point that their grooves are almost gone, replace them. Low-end pads often are molded in one piece with the mounting nut insert or stud, so you just unscrew the old pad and holder assembly and bolt the new one in place. High-end dual-pivot brakes surround the pad with an aluminum holder that is bolted to the brake arm. The pad can be replaced separately by sliding it from the holder. Some pad holders have a setscrew that must first be backed out to free the pad.
Buy the correct pad according to the year and model of brake and material the braking surface is made out of (aluminum or carbon). Sliding the pad in or out of the holder can be difficult, especially with Campagnolo brakes prior to 2015, as those pads are solely a friction fit (Campagnolo pads now have a setscrew-type pad holder, making pad changes simple). With a friction-fit pad, you may have to yank out the old pad with pliers and slide in the new pad with the aid of a vise or slip-joint pliers, or hold the post in a vise while you push on the pad grooves with a screwdriver. Be sure to put the proper pad in the proper holder; look at the old one for guidance. Pads often say R or L on the backside and indicate the forward direction; Campagnolo pads may say DX (right) or SX (left) on the backside.
When you reinstall the pad on the brake arm, make sure that the closed end of the pad holder faces forward. Otherwise, the first time you brake hard, you may see two pieces of rubber fly ahead of you and feel two more hit the backs of your legs. You may not remember anything after that.