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Coefficient of Friction

Coefficient of friction is the ratio of force required to stop an object as it comes in contact with another object, with a specified amount of perpendicular force being applied to the object. For starters, friction is used to describe the amount of attraction, which we commonly attribute to the ability to grip something. As it relates to the braking industry, the coefficient of friction is important because it determines how well a set of brake pads (the object) will react with a given set of brake rotors (contact object) as an automobile is trying to decelerate (the specified amount of perpendicular force).

In this same scenario, the higher the coefficient of friction for a given set of brake pads, the better stopping power the pads will have when applied to the rotor surface. The coefficient measurement ranges from zero to infinity, but most premium pads have ranges from .15 to .65.

A quick and dirty way to determine a relative measure of the coefficient of friction for your brake pads it so look at the coefficient of friction indices stamped on the side of your pads. The indices are a 2 letter rating such as EE, FE, FF or GG, with EE being the least desirable and GG being the most desirable. Most of your ceramic pads have a GG rating, making them a superior friction material for braking power and wear. Ratings of EE and FE indicate that the friction material loses grip as the material becomes heated in high temperatures, thus not able to provide adequate braking.

Another important attribute of the coefficient of friction indices is the fade, meaning how long it takes for the brake pads to cool down. This is important because if a driver is not aware the brakes are getting hotter and does not adjust his driving to compensate, the brake pads can continue getting hotter until the tires burst, or the brake lining catches fire.

One thing to keep in mind when reviewing the quality of brake pads is that there is not a federally mandated standard for aftermarket brake pads. Point in being, customers should always go with OE quality suppliers such as Bendix, Wagner, Raybestos, AC Delco and Akebono. Bendix for example, tests their aftermarket brake pads the same as their OE pads.

In an attempt to set a standard for aftermarket brake pads and brake shoes, the Automotive Aftermarket Industry has recently launched The Brake Effectiveness Evaluation Procedure, commonly referred to as BEEP. The rise of BEEP will ensure a consistency of accepted guidelines for brake pad and brake shoe performance manufactured by QS9000/ISO9001 certified companies. Bendix is currently seeking the BEEP certification on the top numbers of their braking components so they can be awarded the BEEP seal. BEEP certification is not cheap, as it costs around $5000 per part number to be certified, with most manufacturers having 1000’s of part numbers.


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