Brakes are the secret to speed

Many times the secret to speed in a race car is brakes. A properly engineered brake system allows the driver to drive deeper into the corner. When the package is balanced properly, it helps with handling by making sure the car is stable on entry.

  Brake Bias: Race cars must have more brake in the front than the rear. Front-brake bias helps stabilize the front on corner entry and keeps the rear from being loose. Typically, a race car will need about 30 percent more front-braking power than rear. This is achieved by using larger calipers on the front and a smaller front master cylinder.

  Calipers and pads: Choosing brake calipers require thought and research. Factors such as the type of racing, weight of the car, mounting style, etc., need to be considered. Choosing the proper brake pads also requires research. A soft, aggressive compound will provide better breaking but may not last the entire race. For instance, tracks like Martinsville (Va.) Speedway, with a 3,500-pound stock car, are brutal on brakes. The brake pad that gives the best performance may not make it to the end of a 500-lap event.

  Rotors: Most brake rotors are alloys of cast iron, which remains stable under extreme heat. The rotor must be able to withstand extreme temperatures without warping or cracking. Most race cars use vented rotors to help in heat rejection. Proper cooling, using brake ducts, will help keep temperatures in check. Carbon rotors, which are used in Indy cars and other forms of exotic race cars, offer the best braking and work better with increased temperatures.

  Master cylinders: Proper sized master cylinders are crucial to completing an efficient brake system. The bigger the diameter of the cylinder; the harder the brake pedal and the less stopping force at the caliper. The smaller cylinder gives the pedal more travel and feel, letting the driver apply more pressure to the caliper and providing better braking. You need more available pedal travel to take advantage of the smaller diameter. The best system will use two cylinders segregating the front and rear. When sized properly this gives the optimum balance and performance for the brake package. Typically, the front master cylinder will be smaller than the rear.
Using a balance bar allows the master cylinders to work independently from each other. It's adjustable for setting the bias between the front and rear cylinders.

  Brake Fluid: Brakes make heat. Temperatures can soar above 600 degrees. Brake fluid can reach the boiling point, and when it does there is no longer any hydraulic pressure being applied to the caliper. The pedal gets mushy and eventually goes to the floor. Good racing fluid should have a boiling point of at least 550 degrees. Bleed your brakes often and NEVER reuse the fluid. Brake fluid absorbs moisture out of the air, which reduces the boiling point.

  Bleeding: Start by filling the reservoirs on the master cylinders. Bleed the cylinders first. Next go to the calipers farthest from the master cylinders. Use two brake bleed bottles that can be made using clear silicone hose and any plastic bottle. Put one bleed bottle on the front and one on the rear calipers, pushing the hose onto the bleeders.
Start with the inside bleeders. If the system is dry, cycle bleed by opening both bleeders and slowly pumping the fluid into the bottles until all air is gone. Move to the outboard bleeders and repeat. Then go to the other side of the car, repeating the process. After the fluid is clear of air, repeat these steps by pressure bleeding. Depress the pedal building pressure and open the bleeders. Close the bleeders when the pedal hits the floor. Do this until all air is gone.
The right components and maintenance will keep brakes working until the end of the race and help the performance of your race car.

Article by: Chris Paulsen published in "National Speed Sport News" 3/21/07