The size of the master cylinders...
The size of the master cylinders is used to fine-tune the brake balance in the car. For asphalt racing, most drivers use a smaller bore cylinder on the front brakes and a bore one size larger on the rear brakes. Because the front brakes do 75 percent of the braking, this setup gives the front brakes more pressure. Some racers are installing the same size master cylinders and using the balance bar to fine-tune the brakes.
Some racers will drill their rotors, in an attempt to make them lighter. This will only work if you race a light car over a short distance, and your track does not require hard braking. For most Saturday-night racers, drilling the rotor is not advantageous, because the surface temperature of the rotor is hotter than the inte-rior temperature. Every hole has a high thermal gradient. This causes uneven expansion and contraction, which causes cracks. When a rotor cracks, it becomes a boat anchor.
The racer who seeks a lightweight rotor would be better off with a smaller-diameter, thinner-wall rotor. Rotors are designed in different thicknesses to handle a variety of temperature ranges.
Mark Wood at Outlaw Brakes explained the rotor further. "The surface area is the key to the rotor. In curved-vane rotors, the vanes are longer than in a straight-vane rotor. It increases surface area. It offers more area to dissipate the heat. It will be a faster-cooling rotor. The more vanes a rotor has, the more cooling can be done. The downside is that it will be heavier, with more rotating weight. You must determine if the driver is hard on the brakes and needs the extra vanes. If the driver is easy on brakes and doesn't get them as hot, you can go with fewer vanes. The cheapest, lightest-weight rotor is not necessarily the best. If a rotor gets too hot, it radiates heat back into the caliper and boils the fluid. A rotor's diameter and width are determined by your cooling needs. A rule of thumb: You want the biggest-diameter rotor that can fit inside the wheel. Bigger rotors dissipate heat better."
The Master Cylinder
The master cylinder should be matched to the piston area of the front and rear calipers. A master cylinder transforms the mechanical pressure from the pedal into hydraulic pressure, which activates the piston in the caliper. The master cylinder affects both pressure and volume. In general, a smaller master cylinder will provide more brake-line pressure or more braking force. It will give a softer pedal feel because the pedal will travel farther. A larger master cylinder will make less brake-line pressure and less brake force. The pedal feels stiffer because there is less pedal travel.
To determine if your brake...
To determine if your brake system is right for your application, use temperature paint or stickers to record the maximum heat gene-rated by the brakes. Rotors can see 1,000 degrees F. The caliper probably should not be above 400 degrees F. The piston O-rings are a high-temperature material, but can only sustain a temperature of about 300 degrees F.
Most asphalt racers want more front brake than rear brake. If the front and rear calipers are the same size and have the same size pistons, then different size master cylinders can be used to provide more braking for the front. Generally, the front master cylinder is one size smaller than that used for the rear brakes. For instance, use a 7/8-inch on the front and a 1-inch on the rear.
Using separate master cylinders for the front and rear brake systems is beneficial for several reasons. The first is safety. If one system fails, the other system will safely stop the car. Second, different-sized master cylinders for the front and rear brakes allow for tuning the brake balance in the car. The third reason is the ability to fine-tune the brakes, using a balance bar that ties both cylinders to the brake pedal.
Racers must view their brakes as a total system. The ultimate stopping power results from properly selecting the components of the system. It begins with the brake pedal ratio, then goes to the master-cylinder sizing and the proper balance of calipers. It includes the correct size and type of rotor, and concludes with the selection of the brake pad material. All the pieces must work together, or the only way you will stop is to run into something.
Making blind recommendations is dangerous. The choice of calipers depends on the weight and speed of the car, the type and size of track you are running on, the length of the race, and the size and thickness of the rotor. A rule of thumb for asphalt racers would be to use a caliper with bigger pistons in the front of the car and smaller pistons in the rear. This will give around 50-percent-more braking force in the front.