Circle Track Brake Tech

3. What are some common problem areas during the installation of brake calipers and pads?

AP: By far the number-one error in caliper installation is having the caliper too low on the disc. The caliper should be square and true in alignment with the disc, and there must be at least 0.080 inch of clearance [0.100 inch is better] between the outside diameter of the disc and the inside of the caliper disc pathway. The disc expands when hot, and the diameter increases. The caliper will overheat and fail if the disc rubs the inside of the caliper.

Hawk: Not properly bleeding air from the system after installation is common and can create an inaccurate sense of brake performance and effectiveness.

Outlaw: The calipers need to be mounted square and parallel to the rotor. Check the rotor for runout and then make sure the caliper is mounted properly over center. Also, make sure the caliper is mounted square to the centerline, which may require tweaking of the spindle mounts. The calipers should also be mounted so that the pads sit flush to 0.020 inch above the outer edge of the rotor when they are installed. This allows for rotor growth, maximizes the use of the rotor surface, and equalizes the temps on the rotor edge to help avoid unnecessary warping.

Wilwood: The calipers must be aligned laterally over the rotor. They must be square and parallel, with the rotor centered evenly between pistons. The caliper must also be in proper radial alignment, with the outside radius of the pad matched against the outside radius of the rotor. Lateral alignment can usually be corrected with shims between the caliper lugs and mount bracket. Calipers must always be mounted with the bleed screws on top. Otherwise, they cannot be properly bled.

4. How do I properly break in my new pads?

AP: The simple answer is to follow the pad manufacturer's procedure to the letter. Generally, these instructions are in the box of pads, and the manufacturer has done a lot of testing to determine the best procedure for its pads.

Hawk: Most friction manufacturers recommend similar procedures, yet, unfortunately, many racers do not accomplish the most important part of the bedding process, and that's a very slow heat buildup over an extended amount of time followed by a complete cool down. It's highly advisable to follow the manufacturer's recommendation very closely to ensure you get the intended performance from your pads.

Outlaw: Pad break-in may vary depending on the pads being used, but it is generally noted that new pads should be bedded on rotors that have been previously used with the same type of pad. The same applies to rotors. It is a good idea to have your spare pads and rotors bedded, and keep a matched set for that time of need.

Wilwood: The first laps on new pads and rotors are the most critical in their life cycle. Failure to properly bed them can not only result in poor performance, but also irreversible damage to the pads and rotors.

Make a series of six to eight light stops, with a 10-15-second complete release between each stop. Proceed to a series of three to four laps with six to eight medium stops from a slightly higher speed. Proceed further to full-speed laps, making six to eight hard stops to bring the brakes up to real operating temperatures. Then, back off and make a few cool-down laps, using the brakes as little as possible if not at all.

The warm-up cycle involves the driver pushing the brake pedal to make full contact between the brake pads and rotor, then full release of all pressure on the brake pedal to properly warm the parts and bed them in. Open-track practice days present the best opportunity for pad and rotor bedding. It's a good idea to take along a spare set of pads and rotors and bed them during the open-track time.

5. What are some common solutions to bias problems?