Chevy Nova Disc Brakes - Dem's Da Brakes, Part 1

How To Slow The Muscle In Your Musclecar

Mike Harrington May 1, 2008 0 Comment(s)
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Whatever brake pad you use, never ever let them get to this stage. There is nothing left on these pads, and the rotors were chewed up. We took this photo at a shop where they had just been pulled off of a customer's car.

Silicone Base Brake Fluid (SBBF)
The U.S. DOT defines silicone brake fluid as that which consists of no less than 70 percent of adiorgano polysiloxane by weight. Silicone-based fluids are regarded as DOT 5 fluids. They are highly compressible and can give the driver the feeling of a spongy pedal. The higher the brake system temperature, the more the compressibility of the fluid-increasing the feeling of a spongy pedal. Silicone-based fluids are non-hydroscopic, meaning they will not absorb or mix with water. When water is present in the brake system, it will create a water/fluid/water/fluid situation. Because water boils at approximately 212 degrees Fahrenheit, the ability of the brake system to operate correctly decreases, and the steam created from boiling water adds air to the system. It is important to remember that water may be present in any brake system. Therefore, silicone brake fluid lacks the ability to deal with moisture and will dramatically decrease a brake system's performance.

Brake Pads
Every vehicle owner wants brake pads that are quiet yet grab like an eagle's talon and leave very low dust. Good luck on that, as with all things automotive there is a compromise. Brake pads are the sacrificial lamb in the brake system. They will all wear down and reach the point of no return and eventually need replacing.

Brake pads are like Coke and Pepsi. Both have similar ingredients, yet each company mixes their various ingredients differently, and each company has their secret mix that the other guy may not have. Yet both can be classified as a cola. Just like Coke or Pepsi, each brake pad manufacturer keeps their specific pad compound a secret. Surprisingly, the government regulations and definitions that apply to brake fluids and their chemical makeup don't apply to brake pad manufacturers. Nearly all brake pads contain similar types of materials such as copper, brass, steel, etc. Brake pad compounds can be a very deep and broad subject. Rather than speculate about the chemical makeup of brake pads and their performance, we went straight to the source and asked the professionals at Hawk Performance to define and explain the difference in pads in layman's terms.

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Organic Pads?
Organic brake pads are defined as friction materials with less than 20 percent metallic content. Historically, most organic brake pads contained asbestos, which is now classified as a hazardous material. Today, the organic pads used in the United States are identified as NAOs (Non-Asbestos Organics).

Advantages of NAO
Low dust output
Minimal NVH (noise, vibration and harshness)
Low rotor wear

Disadvantages of NAO
Low coefficient of friction (stopping power)
Poor resistance to elevated temperatures (over 450 F), causing brake fade
High brake pad wear rate

What are semi-metallic pads?
Semi-metallic brake pads are defined as friction materials with more than 20 percent metallic content, but with less than 75 percent metallic content. Because the definition is so broad, some companies have adopted the terms "low met" and "high met" to indicate at what end of the spectrum their product could be categorized. Semi-metallic friction materials are the most widely used technology for automotive disc brake pads.

Advantages of Semi-Mets
Medium to high coefficient of friction
Excellent resistance brake fade at low to high temperatures (1,000 F)
Very good pad wear

Disadvantages of Semi-Mets
Slightly higher dust output than organics
Minimal noise output, but greater risk of NVH issues with poorly engineered formulations
Good rotor wear but slightly greater than NAOs


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