Some myths about
brake systems make sense and seem to explain a problem, but they do not resolve the real issues. A lot of these myths are built from outdated history and should just go away. Here are seven myths about
brake pads and
brake rotors that can hinder efforts to
solve brake problems.
MYTH: Heat is what determines the Minimum Thickness Specification of a Brake Rotor Heat has nothing to do with this specification. The minimum thickness is based on how far the
brake caliper piston will travel if the
brake pads were worn all the way to the backing plates. If your
brake pads or
brake rotor were worn to below specification, the
caliper piston could extend past the bore and start leaking.
MYTH: There are "Soft" and "Hard" Brake Pads The average driver thinks of a "hard"
brake pad as semi-metallic and a "soft" pad as typically an organic or ceramic. Both of types of friction materials can be the same in terms of compressibility. Calling one material soft and one hard is not accurate. Compressibility can influence pedal feel, but usually only when the
brake pad is defective. What really influences pedal feel is the pad's coefficient of friction. Engineers measure compressibility as a quality control measurement and not as a performance measurement and it has very little to do with noise or rotor wear.
MYTH: Brake Line Damage Can Cause Brake Drag All modern
brake lines are usually composed of two or three layers with a stiff internal liner that is in contact with the fluid. The outer layers are typically a softer material designed to absorb impacts with road debris. If the
brakes are stuck on just one wheel, a mechanic could assume that it is a restriction from inside the
brake hose where the inner liner was damaged and created a flap that prevents the pressure from releasing the
caliper. This could possibly be the cause, but usually if the
brake line was damaged the entire liner would fail and the
brake fluid pressure would make the hose bulge or burst. The restriction is more likely to be from stuck
emergency brakes, caliper slides, brake booster, or valve problems.
MYTH: Wet Brakes Increase Stopping Distances If you have
drum brakes it might be a good idea to tap the brake pedal after you drove through a deep puddle to clear the water from the
brakes, but with
disc brakes this has become unnecessary. If the wheels are turning, water will be thrown away from the
brake rotor by centrifugal force.
MYTH: Brake Pads are Regulated by the Government There are no government regulations concerning the performance of
aftermarket brake pads.
MYTH: Brake Pads Need to Warm Up Most
brake pads are designed to produce an even amount of
brake torque across a wide spectrum of temperatures, including at very low heat. This is true for the exotics with carbon ceramic brakes as well as
for standard everyday vehicles. The exception to this would be racing quality pads that require heat to generate its highest coefficient of friction. Manufacturers of these pads will specify these pads are only for off-highway racing purposes, and would not be something most mechanics would recommend.
MYTH: Brake Pads Are The Source of All Brake Noise All
brake pads produce vibrations when they are applied. But only if the vibrations are transferred to the vehicle, will a driver actually hear it. Typically, most high frequency noises come from the
brake caliper,
brake rotor or bracket. Low frequency sounds are usually caused more by the body structure of the vehicle. What usually causes
brake pad noise is a change in the material due to heat. A more consistent friction material causes less vibrational excitation variation at the friction coupling by having consistent brake torque at environmental extremes of humidity and temperature. A few options to solve
brake pad noise are to isolate the brake pads with lubricant, shims, and renewing the
brake hardware.