Why do some brake discs rust easily?

Rust on the brake disc is a common phenomenon. If your car stops for a few days and it rains again these days, there is a high probability of rusting. Brake discs, like brake pads, are very important components of the braking system. They are accessories that need to be replaced regularly and are considered consumables. 

Let's talk about the rust of brake discs first. It is normal for them to rust. It will not affect the braking performance, nor is it a quality problem of the brake discs. You can use them with confidence. Even if they are rusted, driving a certain distance and stepping on the brakes a few times will grind away all the rust and make them smooth and shiny again. The reason for the rust is its material and the environment in which it is used. The main material of the brake disc is cast iron, and cast iron itself is very easy to rust. 

If it rains when the vehicle is parked, or the environment is humid, the brake disc will be exposed to this environment for a long time, and the moisture in the air will react chemically with the iron in the cast iron to form iron oxide, which is rust. If the vehicle is not driven for three or four days in humid weather or rainy seasons, the brake disc will rust. 

The brake disc is more likely to rust when it is stationary for a long time.

If you drive every day, the environment of the vehicle will change and it will not be in a humid environment all the time. The most important thing is that as the brakes are used, the temperature of the brake disc will rise, which will dry out the moisture. As long as the surface of the brake disc is dry, it will not rust.

In addition, even if there is a small amount of rust, it will be worn away by the friction between the brake pads and the brake disc. In short, rust is a normal phenomenon.

If you don't drive for a long time, the vehicle needs to be parked in a ventilated and dry place, and cannot be parked in a long-term humid place to prevent the brake disc from rusting too seriously and being completely damaged.

Let's talk about the second aspect. Why is the surface of the brake disc worn unevenly and has grooves?

This is caused by the brake pad being too hard. When braking, only the brake pad and the brake disc rub against each other, so the grooves on the brake disc must be caused by the brake pad. Because some wear-resistant materials are added to the brake pad during manufacturing, among which there are relatively large and hard metal particles. When these metal particles rub against the brake disc, they will grind out grooves on the brake disc.

If the groove is shallow, less than 1 mm deep, it means that the hard particles are not too large, no special treatment is required, and it will not affect the brakes, and the vehicle can be used normally.

Of course, if the groove depth is deeper, exceeding 1 mm, then the brake pads need to be processed. Remove the brake pads and grind them to remove the hard metal particles, and this situation will not occur during use.

If there is a shake when braking, it means that the brake disc has been worn unevenly, and the brake disc also needs to be removed and polished. Therefore, when replacing brake pads, you must choose brake pads with reliable quality and stable friction coefficient to ensure the uniform distribution of friction during braking and reduce the uneven wear of the brake disc.