- Pedal Travel
- Brake Fluid
- Caliper Deflection and Twist
- Calipers and Pad Shear
- Master Cylinder
- Brake Ducting
- RMS Factor
- Bleeding the Brake System
- Piston Materials
- Brake Bias
Pedal travel can be attributed to pad taper, air or moisture in the brake fluid, boiled brake fluid, caliper deflection, cocked pads in the calipers, incorrect pedal ratios, and accelerated pad wear. Use hard brake line as much as possible and keep stainless flex line to a minimum. Even a stainless flex line, while better than a rubber hose, will still expand under pressure. Also, check the hard line, all connections, and piston seals for leaks. Stiffer calipers can reduce pedal travel. Also, remove tapered pads, as they will cause the piston to cock and make the pedal feel long.
There are two types of brake fluids, glycol bases and silicone based. Glycol based is most commonly used in racing applications. While glycol based fluid does have a tendency to retain moisture, at high temperatures it is less compressible than other types of fluids, and thus gives the driver a less spongy pedal. Racing brake fluids tend to retain moisture if left exposed to air. The moisture (water) trapped in the fluid bubbles when heated and forms small air pockets. These pockets are compressible and result in a spongy brake pedal.
Caliper Deflection and Twist
caliper deflection is the spreading motion of the caliper as pressure is applied on the pistons. As calipers wear out the spread tends to increase, thus forcing the pistons to travel further before the pads engage the rotor to the full extent of the line pressure. Sometimes caliper twist occurs when the racer is using very high coefficient racing brake pads, which result in an increased output of torque and causes the caliper to twist and/or thrust forward. The twisting effect causes the caliper to deflect away from the rotor and bend the bridge between the inboard and outboard sections of the caliper. This increases the pressure on the calipers and may cause them to bend out of shape; if they are not reinforced or designed to absorb this constant stress.
Calipers and pad Shear
caliper shear is when the bolts that hold the caliper to the mounting brackets fail. This can happen in three ways: 1. The bolts are defective, 2. The bolts have very low shear strength, & 3. The caliper is not properly installed.
Pad shear is when the friction material tears away from the pad backing plate. This is due to a failure of the adhesive or other retention devise between the pad and backing plate.
The primary role of the master cylinder is to transfer kinetic energy from your foot to the caliper, via the brake line. The secondary task of the master cylinder is that of brake line fluid displacement. If the master cylinder is working well this displacement is minimal. The master cylinder reservoir stores the brake fluid, which is transferred to the master cylinder if necessary. There is a piston in the master cylinder, which is connected to a rod that is attached to the brake pedal assembly. Applied pressure on the brake pedal moves the master cylinder piston, which generates pressure through the bore hole, down the brake line, into the caliper, causing the brake pads to clamp down on the rotor.
Brake ducting is done to
cool the brake system. The focus of the ducting should be to force
heat away from the brake system. Cool air should be forced in the
most direct manner across or up through the center of the rotor
and then away from the brakes and out of the area. The less bends
and turns in the ducting the better the system. Duct size should
be as big as the application will allow and directed in the shortest
and straightest route possible. If racing on dirt, screens should
cover the ducts.
This stands for Root Mean
Square, which is the standard for measuring the finished surface
of an object. This is mostly used in reference to rotors when judging
the suitability of their surface.
the Brake System
There are numerous methods for bleeding your brake system. There is the pressure bleeding, manual bleeding, gravity bleeding, and vacuum bleeding methods. All four have their advantages and disadvantages. We recommend that you bleed your brakes as often as possible, never reuse brake fluid, and always replace the fluid with high temperature brake fluid.
The primary materials for pistons are titanium and stainless steel. These materials are used as insulators between the hot brake pads and the brake fluid because of their low thermal conductivity.
This allows the driver to alter the line pressure differential between the front and rear brakes. The goal is to balance your braking system so both front and rear systems reach lock up simultaneously. The best way to tune your brake bias for pavement is to start with the front bias. Keep moving the bias to the rear until the rear brakes lock up, then back off towards the front brakes. The opposite is used for dirt applications.