High Friction Coefficient: The semi – metallic brake pads mixture contains a significant amount of metal fibers (usually around 30% – 70% of the total composition). This high metal content provides a high friction coefficient, typically ranging from 0.4 – 0.6. As a result, it offers excellent braking performance, making it suitable for heavy – duty commercial vehicles that need to stop quickly. For example, in emergency braking situations, a semi – metallic brake pad – equipped truck can come to a halt more rapidly compared to some other formulations.
Good Heat Dissipation: The metal fibers, such as steel or copper, act as efficient heat conductors. They can dissipate heat at a relatively high rate, up to 1000 – 1200 watts per square centimeter. This property is crucial for commercial vehicles that often experience heavy braking, as it helps prevent brake fade. Brake fade occurs when the brakes overheat and lose their effectiveness. With semi – metallic brake pads, the risk of brake fade is significantly reduced, ensuring consistent braking performance during long – distance hauls and mountainous driving.
Durability: The robust nature of the semi – metallic brake pads mixture gives it good durability. The metal components enhance the structural integrity of the brake pads, allowing them to withstand the high – pressure forces during braking. They can last for a reasonable mileage, usually around 30,000 – 50,000 miles for commercial vehicles, depending on the operating conditions.
Disadvantages
Noise and Vibration: One of the main drawbacks of semi – metallic brake pads is the noise they produce. During braking, especially light braking, the metal – on – metal contact can result in squealing or grinding noises. These noises can range from 60 – 70 decibels, which can be quite bothersome and may even indicate potential wear or damage. Additionally, the hard metal components can cause vibrations that can be felt through the vehicle’s chassis and steering wheel.
Rotors Wear: The high – friction and abrasive nature of semi – metallic brake pads can lead to more wear on the brake rotors. Over time, this can reduce the lifespan of the rotors and increase maintenance costs. The wear rate of the rotors with semi – metallic brake pads can be approximately 0.1 – 0.2 millimeters per 10,000 miles, which is relatively higher compared to other formulations.
Dust Production: Semi – metallic brake pads tend to produce more brake dust. The metal particles that wear off during braking can accumulate on the wheels and other parts of the vehicle, not only affecting the appearance but also potentially causing damage to other components if not cleaned regularly.
2. Low – Metallic Brake Pads Mixture
Advantages
Balanced Performance: The low – metallic brake pads mixture contains a reduced amount of metal (usually around 10% – 30%) compared to semi – metallic pads. This, combined with other components like organic fibers and friction modifiers, provides a more balanced performance. The friction coefficient is typically in the range of 0.35 – 0.45, which is still sufficient for most commercial vehicle braking requirements while offering a smoother braking experience.
Reduced Noise: With less metal – on – metal contact, low – metallic brake pads produce significantly less noise. The noise level during braking can be as low as 40 – 50 decibels, which is much quieter than semi – metallic pads. This makes for a more comfortable driving environment for the vehicle operator and passengers.
Less Rotor Wear: The lower metal content and the presence of other softer components in the mixture result in reduced wear on the brake rotors. The wear rate on the rotors can be approximately 0.05 – 0.1 millimeters per 10,000 miles, which is about half that of semi – metallic brake pads. This can lead to longer rotor lifespan and lower maintenance costs in the long run.
Disadvantages
Slightly Reduced Heat Dissipation: Although the low – metallic brake pads can still handle heat reasonably well, their heat dissipation capabilities are not as efficient as semi – metallic pads. They can dissipate heat at a rate of around 600 – 800 watts per square centimeter. In situations where the vehicle is subject to continuous and heavy braking, such as in stop – and – go traffic with a heavy load, there is a slightly higher risk of brake fade compared to semi – metallic pads.
Moderate Durability: The reduced metal content may lead to a slightly lower durability of the brake pads. They typically have a lifespan of around 25,000 – 40,000 miles for commercial vehicles. This means they may need to be replaced more frequently than semi – metallic pads in some high – usage scenarios.
Exceptional Heat Resistance: The carbon ceramic brake pads mixture, with its carbon ceramic brake pads formula, is designed to withstand extremely high temperatures. The ceramic components, such as silicon carbide and alumina, can handle temperatures up to 1000 – 1200°C without significant degradation. This makes it ideal for commercial vehicles that operate in extreme conditions, like high – speed long – distance transportation or in mountainous regions with steep descents.
Low Noise and Vibration: Carbon ceramic brake pads are known for their quiet operation. The carbon ceramic brake pads friction materials and the presence of ceramic brake pads powder result in a smooth braking process with minimal noise and vibration. The noise level during braking is usually below 40 decibels, providing a quiet and comfortable driving experience.
Long Lifespan and Low Wear: The combination of carbon and ceramic materials in the mixture offers excellent wear resistance. The brake pads can last for a long mileage, often exceeding 60,000 – 80,000 miles for commercial vehicles. Additionally, the wear on the brake rotors is minimal, with a wear rate of approximately 0.03 – 0.08 millimeters per 10,000 miles. This not only reduces maintenance costs but also ensures consistent braking performance over a long period.
Disadvantages
High Cost: The production of carbon ceramic brake pads involves advanced materials and complex manufacturing processes. As a result, they are significantly more expensive than semi – metallic and low – metallic brake pads. The cost can be two to three times higher, which may be a deterrent for cost – sensitive commercial vehicle operators.
Initial Braking Performance: Carbon ceramic brake pads may have a slightly lower initial friction coefficient compared to semi – metallic pads. Their friction coefficient is usually in the range of 0.3 – 0.4 during the first few applications. This means that they may require a slightly longer braking distance in the very first few stops. However, once the brake pads and rotors have “bedded – in” (a process where a thin layer of friction material is transferred to the rotor surface), the braking performance becomes excellent and consistent.