Coefficient of Friction - A number measuring the “grip” of a material used in brake pads.

Coefficient of friction can vary depending on the type of material used for the brake rotor. Typically service brakes are concerned with dynamic coefficient of friction, or the coefficient of friction measured while the vehicle is moving. Below are a few of the main characteristics. Depending on the desired performance, the characteristics can be minimized or maximized.

1. Speed Sensitive - Coefficient of friction typically drops as the speed of the vehicle increases.
2. Pressure Sensitive - Coefficient of friction typically drops as more clamp force is generated.
3. Temperature Sensitive - Coefficient of friction typically drops as the temperature of the brake system increases.

An engineer would use the formula “W” where “F” equals the force necessary to move a body in contact with another, and “W” equals the weight of the body. Thus if a car weighing 1,000 pounds had all wheels locked and it took a pull of 300 pounds to move it on a level road, the coefficient of friction of the road surface and tires would be .333, or 300 divided by 1,000.

Heat, dampness, speed of movement and many other factors cause the coefficient of friction to vary, so that it is a relative term, rather than a positive measurement.

The term “coefficient of friction,” as applied to brake lining, refers to the friction between that particular pad and the disc.

The coefficient of friction also effected from cleanliness of the pad surface and surface roughness.

Typical Friction Coefficients: 0.35 µ —  Original Equipment
0.38 µ —  PBR Ceramic
0.45 µ —  Pagid RS4-2-1 Black
0.48 µ —  Pagid RS4-2 Blue
0.50 µ —  Ferodo DS2500
0.52 µ —  Pagid RS4-4 Orange
0.52 µ —  Ferodo DS3000 Enduro
0.54 µ —  Pagid RS19 Yellow
0.57 µ —  Pagid RS14 Black
0.62 µ —  Ferodo DS3000
0.68 µ —  Pagid RS15 Grey
0.68 µ —  Ferodo DS3000 plus