What is the Standard for Brake Pad Friction Coefficient?
2 Answers
The friction coefficient standards are as follows: Class 1: 0.20~0.70 at 200°C; Class 2: 0.20~0.70 at 250°C; Class 3: 0.20~0.70 at 300°C; Class 4: 0.25~0.70 at 350°C. Below is relevant information about brake pads: 1. Brake pad classification: semi-metallic brake pads, low-metallic brake pads, NAO formula brake pads, ceramic brake pads, and NAO ceramic brake pads. 2. Ceramic brake pads vs. traditional brake pads: In traditional brake pads, metal is the primary material generating friction, providing strong braking force but with significant wear and a tendency for noise. After installing ceramic brake pads, abnormal squealing does not occur during normal driving. 3. Stable friction coefficient: Ordinary brake pads have immature friction materials, and excessively high friction coefficients can lead to unsafe factors such as loss of directional control during braking, pad burning, and scratching of brake discs. Even when the brake disc temperature reaches 650°C, the friction coefficient of ceramic brake pads remains around 0.45-0.55, ensuring excellent braking performance for the vehicle.
When I first started working at an auto repair shop, I often dealt with issues related to the friction coefficient of brake pads. The standard range is generally between 0.35 and 0.45, primarily defined by specifications like the American SAE J661 standard. This coefficient directly affects braking force—if it's too high, say above 0.5, the brakes may feel overly sensitive but risk sudden lock-up; if it's too low, below 0.3, the braking will feel sluggish and increase stopping distance. Testing must account for temperature variations, as the coefficient decreases under high temperatures, leading to brake fade during mountain driving or long descents. Standards vary slightly between brands or models—for example, Japanese cars often use the lower limit for comfort, while German cars lean toward the upper limit for enhanced performance. Always refer to the manual or manufacturer recommendations when selecting brake pads, and before installing new ones, check professional repair manuals to ensure compliance and driving safety.