- BRAKE ROTOR BREAK IN PROCEDURE
- BRAKE FLUID
- BLEEDING THE BRAKE SYSTEM
- MASTER CYLINDERS
- BRAKE CALIPERS
- DUCTING AIR TO BRAKE SYSTEM
- ROTOR AND BRAKE PAD TEMPERATURE
- OVERALL BRAKE SYSTEM MAINTENANCE
- RECOMMENDED BRAKE TIPS
It is very important to understand the manufacturer's recommendations in regards to bedding in your new brake pads and rotors. The following guidelines will help assure you that the correct steps are being taken. Some brake pad companies, offer pads that are designed with a unique processing stage called burnishing. Burnishing simulates the first few minutes of a pad on the racecar by applying heat and pressure to the pad while in the final stages of production. This process is a great advantage to you because the break in or bedding procedure normally needed with other types of brake pads has already been started before you install the pads. This eliminates the cost normally associated with bedding in brake pads because you will not need to use your motor, tires, and fuel to prepare your brake pads for racing. It is important to build heat in the pad prior to racing. This step can be done simply by dragging the brake while entering the track or by making two or three hard stops just before taking the green flag. Remember most brake pads operate best at higher temperatures, so it is best to heat them up before each race by following the above steps. Non-burnished racing brake pads will require a bedding in procedure that will differ slightly between manufacturers. The following is a guide that covers most manufacturers' recommendations (it is best to contact the manufacturer for exact instructions). 1. Slowly build heat in the pad by making slow stops, being sure to allow a minute or two for the pad to cool down while the car continues to move. 2. Repeat above step two or three times. 3. At full speed make hard racing type stops again, allowing cool down time between stops. 4. Repeat above steps two or three times or until brake fade is noticed. 5. Allow brake system to completely cool. Your pads should now be race ready. (It is important to remember that the pad and rotor surface must be mated to each other before ultimate performance will occur.)
ROTOR BREAK IN PROCEDURE
Again it is very important to know and understand the manufacturer's recommendation for this step. The following is a guide that covers most manufacturers' recommendations: new rotors should be heated up very slowly and, if possible, use a set of pads that have already been exposed to racing use. For best results, break in the rotor with the same type of brake pad (compound) that you intend to use with the rotor. This will help assure that different friction materials will not build up on the rotor. After the above step has been completed, inspect the rotor-rubbing surface. A uniform polished appearance with no cracks or grooves is what you should find.
Many brake system problems are caused by old or inadequate brake fluid. It is very important to always use a high quality fluid with a high dry boiling point rating. There are also many theories as to what type of fluid should be used. The following information should help you better understand the differences regarding different types of fluids. A. Silicon based fluids: most all silicon-based fluids are very easy to compress. When using a fluid that is easier to compress it must be noted that a spongy pedal will likely be noticed. Many times the pedal will continually get even spongier as the fluid gets hotter. Another characteristic about silicone fluid, is its inability to mix with water. When the water begins to boil, it can cause the system to air lock. It should also be noted that silicon based fluid is not recommended in AFCO type master cylinders. B. Glycol based fluids: theses types of fluids are the most widely used and maybe the least understood. It is very important to understand that this fluid will mix with water. It is also important to remember that the boiling point of the fluid will drop considerably as the fluid mixes with the moisture in your brake system, making it extremely important to completely purge the entire system very often. No matter the type of fluid you choose, it is a good idea to change it often and never use fluid from an open container because of the potential for moisture.
BLEEDING THE BRAKE SYSTEM
To assure yourself of a properly bled system, the following guidelines should be followed: always use new fluid. (DO NOT REUSE NEW fluid.) Always use a clear hose and container so you can view the fluid as it exits the system. Always begin bleeding with the furthest caliper from the master cylinder. Always push the pedal slowly all the way down and allow pedal to remain up momentarily to refill master cylinder bore. DO NOT jab the pedal. Only open bleeders the amount needed to spray fluid out. Opening bleeders too far can cause air bubbles to form. While pressure bleeding is much easier than manual bleeding, it is important to manually bleed the system every so often. This allows a check of fluid flow that would not normally be seen while using the pressure bleeding method.
It is important to match the proper size master cylinder with the vehicle's weight, type of racing, and driving style. Several important points to remember are as follows: the smaller master cylinder bore will create higher pressure in the system. The larger master cylinder bore will create more volume in the system, and will tend to give the pedal a firmer feel and less pedal travel.
Caliper selection is a very important part of a correctly operating brake system. The type of racing, weight, car, surface, and driving style are all elements that should be considered when choosing a selection of calipers. Besides the overall size and style of the caliper, it is important to know what size caliper pistons will be best for your application. Larger pistons will create more pressure on the brake pad backing plate. The opposite is true with small caliper pistons. Some calipers are designed with multi size pistons to aid in proper proportioning of brake pressure and help assure less pad taper.
DUCTING AIR TO BRAKE SYSTEM
Heat created by brake system components can sometimes cause problems that are hard to diagnose. Many times racers blame the problem on brake pad fade. Fade is almost always caused by heat. In most cases, removing the heat from the rotor and caliper area can rid the system of fade. The important thing to remember, and what is very misunderstood is ducting should be used to force hot air away form the hot component, not blow cool air on it. By removing the heat, the component will operate cooler. For best results, force cooler air across the components making sure that the air that is being removed has a path to follow that will not allow the heat to build up someplace else. Duct size should be as big as the application will allow, and directed in the shortest and straightest route possible. It may be helpful to experiment with duct locations. On dirt cars try to install the duct in areas that don't see an excessive amount of dirt or mud, and install a fine mesh screen in the duct hose to help trap air borne dirt. On asphalt and road racecars, try to install duct on flat areas, avoiding areas that allow air to pass over the duct inlet. If the application allows, use one duct hose directed to the center of the rotor, and another directed to the caliper area, preferably directed down toward the top of the caliper; this will force hot air from the pad area. Many types of ducts are available with many applications. Be certain to match the correct duct with you application.
ROTOR AND BRAKE PAD TEMPERATURE
Before choosing a brake pad (compound), it is very helpful to know what temperature your system operates at. System temperature will change depending on the size of track and driving style. It is very important to factor in the change to assure your system works correctly. Most racing pads work best at certain temperatures. Running a pad that works best at very high temperatures will not give the best results if the temperature is lower than the specified range. The same is true when using a low temperature pad in a high temperature situation. Many problems can be avoided by using heat sensitive paint on rotors, pads, and calipers. This type of paint burns off when the specific temperature is reached; allowing you to pinpoint how hot the component is getting during race conditions. Tire pyrometers can not accurately tell you what temperature the components are because of the cool down time involved.
OVERALL BRAKE SYSTEM MAINTENANCE
Proper brake system maintenance is essential to assure the best performance and long life of your system. Always use a checklist in regards to weekly maintenance. Sometimes overlooked items that should be checked for include checking for misaligned caliper brackets and loose caliper bolts. Inspect all lines and fittings for even the smallest leak. Reposition and monitor air ducting placement. It is also a very good idea to remove the pistons from the calipers and inspect them for abnormal wear. Never replace used caliper O-rings after removing them from the caliper. rotors and pads should be checked for extensive cracking and wear rate. Always examine the tabs or ears on the rotor, looking for any signs of warping, cracking, or any other unusual signs of wear.
- RECOMMENDED BRAKE TIPS
Always use fresh high temperature fluid. Completely drain and purge system often.
• Follow a checklist regarding brake system maintenance.
- • Never hold hot brakes on for long periods while not moving.
- • Know your operating temps, and monitor temperature when changing components.
- • Replace caliper O-rings often.
- • Use hard brake line wherever possible.
- • Use safety wire to secure rotor and caliper bolts.
- • Mount calipers with bleed screws up.
- • Only use residual pressure valves as a last effort.
- • Try to maintain between 800 and 1200 psi in your system. (Never exceed 1500.)
- • Bleed dual master cylinders separately by disconnecting push rod from balance bar on first master cylinder, and then repeat on the second.
- • For best results, use the same rotor and pad compound combination to help guard against glazing of pad or rotor surface.
- • When changing pad compounds, bead blast rotor friction surface to remove old pad material buildup.
There are many more situations, causes, problems and items to check for, and too many to list. We hope you now have a better understanding about your system. If you have any questions, or need assistance with a problem, please contact your local AFCO dealer, or call the AFCO tech line at (812) 897-0900.