Let get know the car brake system.
The brake pad is a tool to create friction when pressure is made on the brake disk or drum brake. The material and texture of the brake disk or drum brake must be hard, and at the same time not slippery, in order to delay erosion. Brake pad must be softer than disk or drum, in order to provide a higher rate of friction, and hence, erosion, as it is easy to replace. Brake disk can be composed of several materials, including soft metal, in order to provide better ability to brake while moving at high speed.
In the past, the fibrous silicate mineral known as asbestos was used as the main ingredient of the brake pad. As such, when the brake pad eroded, it may have become white powder that did not stick to the wheel rim, but instead created air pollution, which in turn, damaged respiratory system of the livings. As such, graphite/carbon is the material that is being used instead, which produces black powdered stain when the brake pad erodes. It may look dirty, but it is harmless.
Brake pads come in many different effectiveness levels and degrees of solidity. Please keep the following principles in mind when selecting the brake pad: the softer the brake pad, the more friction it can create, but the heat-resistance level is low and it may be slippery or easily burnt when stepping on the brake a lot or braking at high speed; the harder the brake pad, the more heat-resistance level, and also higher ability to brake at high speed though it needs to be warmed up first; and the ability to brake at low speed is quite low.
Keep these principles in mind and select a suitable type of brake pad for your driving characteristic and your car’s performance.