Due to the extreme temperatures that high performance brake systems operate at, standard fluids are not recommended. XP Motorsports recommends a dot 4 Hi-performance fluid with the dry boiling point of 466 degrees F minimum and a wet boiling point of 311 degrees. Dot 5-silicone fluid is not recommended because water will collect in your system causing lower boiling points and vapor lock. Dot 5 fluid is also a highly compressible fluid and will cause your pedal to feel spongy.
Bleeding Your Brakes
When bleeding your brakes, make sure the bleed screws are pointed up. Always start with the caliper farthest from the master cylinder. Have one person open the bleed screw while another person slowly depresses on the brake pedal. Close the bleed screw before brake pedal is released. Have someone keep checking the fluid in the master cylinder. Never let the level get low. Never put fluid drained out of the system back into the master cylinder.
Brake calipers need to be mounted square to rotor for proper performance. After caliper is mounted onto the bracket, have someone apply the brakes while the caliper is being observed. Only the pistons and pads should move.
The bore size of the master cylinder influences the obtainable line pressure. In racing applications where only rear brakes are used a 7/8” master cylinder is needed. If single piston front brakes are used in conjunction with rear brakes a 1” master cylinder will work. For applications using a 4 piston calipers front and rear a 1 1/8” master cylinder is recommended.
New brake pads require bedding in process. This bedding in procedure starts by pumping your brakes at a very low speed to assure proper brake operation. Then make a series of hard stops from moderate speeds until some brake fade is felt. Park your car and allow brakes to cool completely. Proper breaking in of pads and rotors will result in greater performance and longer wear.Failure to properly bed in your brakes could lead to friction material to flake and break up resulting in fast pad wear and pad loss, or could lead to over heating your pads and causing them to glaze over resulting in car not being able to stop. Brake pads should be checked regularly. If pads are wearing evenly, the pads can be used almost down to the backing plate.
rotors just like pads need to be bedded in. This process is the same as the
brake pads. Proper bedding will increase the rotor life and make it more
resistant to thermal cracking. Any pulsation feel will go away after
several repeated hard stops. Rotors are
ground to ensure the rotor is flat but sometimes hubs, bearings, or hats have
runout that causes the rotor to runout. You can adjust the runout by placing
shims between the rotor and hub, or hat. Allowable runout is .005-. 008. Some
runout is acceptable
if you are not experiencing brake drag, pedal pulsation or piston knock back.
Brake Pedal Ratio
Improper pedal ratio is the most common cause of poor operation of brakes. The pedal ratio must be great enough to produce 1200-PSI system pressure under severe braking conditions, We recommend using a pressure gauge connected to the system to verify the maximum available pressure before running the car. Start with a pedal ratio of 6:1 and adjust if needed.
Residual Pressure Valves
Normally residual pressure valves are not recommended. However, on certain cases when the calipers are mounted at the same level or higher than the master cylinder a 2-pound residual valve is necessary to prevent backflow from the caliper to the master cylinder. If a residual valve is needed it should be plumbed just outside the master cylinder or as close as possible to the master cylinder.
A proportioning valve restricts pressure to a portion of the braking system, with this in mind the valve should be installed on the brake line in which pressure needs to be reduced. A typical street vehicle normally will use a proportioning valve in the rear line, due to most braking is done with the front wheels. A drag racing vehicle or any vehicle using a 3.5 front wheel normally will use a proportioning valve on the front line since most of the braking will be done with the rear wheels. An adjustable valve should be used so that you can fine-tune the brakes to your particular car.
Disc Brake Maintenance
1. Bleed each caliper on your car.
2. Replenish your brake system with fresh brake fluid.
3. Check for leaks around pistons and fittings of each caliper.
4. Check for leaks at any and all fittings.
5. Replace any pads that are worn down.
6. Check for any burrs or dings on exposed area of piston to prevent damaging the internal seals during piston retraction.
7. Make sure all wheels rotate freely.
8. Check all bolts for secure tight fit.
9. Clean brake dust from calipers, rotors, and wheel