Some time ago, a Mercedes Benz car came to the maintenance shop. At present, the car has driven more than 85000 kilometers. The owner described the fault to the repairman. Now his car can always hear squeaking noises when driving or stepping on the brake, and the brake fault light is on and does not go out.

其实，这辆奔驰车在上次做保养的时候，修车师傅就检查到该车的刹车片该换了，可能当时车主确实有事，也或许是不太相信修车师傅所说的话，反正当时给推辞了没有更换，这不跑了还不到1千公里就出现了问题。

In fact, when the Mercedes Benz was serviced last time, the repairman checked that the brake pads of the car should be replaced. Maybe the owner was really busy at that time, or maybe he didn't believe what the repairman said. Anyway, he refused at that time and didn't replace it. After not running for less than 1000 kilometers, there was a problem.

由于修车师傅已经知道哪里出了问题，所以接过车后就直接就把刹车片拆了下来，从下图中可以看到，刹车片上的报警线已经被磨损去了一大半，这就证明刹车该换了。

Since the repairman already knew what was wrong, he directly removed the brake pad after receiving the car. As can be seen from the figure below, more than half of the alarm line on the brake pad has been worn, which proves that the brake should be replaced.

奔驰车主看到刹车片磨成这般模样，毫不犹豫同意修车师傅更换掉，下图这是修车师傅让车主观看新旧刹车片的对比，左边的新刹车片明显要比右边的旧刹车片要厚很多。

The owner of Mercedes Benz saw that the brake pads were ground like this and did not hesitate to agree to the repairman to replace them. In the figure below, the repairman asked the owner to see the comparison between the old and new brake pads. The new brake pad on the left is obviously much thicker than the old brake pad on the right.

不过修车师傅在拆卸刹车片的过程中，还发现因刹车片没有及时更换，还导致了刹车盘受到了一定的磨损，刹车盘的边缘凸起了很多，修车师傅表示，这一情况是需要处理的，不然安装上新刹车片后就会出现异响的问题。如下图所示；

However, in the process of removing the brake pads, the repairman also found that the brake pads were not replaced in time, which also led to certain wear on the brake discs, and the edges of the brake discs bulged a lot. The repairman said that this situation needs to be handled, otherwise there will be a problem of abnormal noise after installing new brake pads. As shown in the figure below;

奔驰车主得知这一问题后，赶紧问修车师傅这该怎么处理呢？只见修车师傅把刹车盘拆卸下来，之后固定在一个机器上便开始打磨了起来。修车师傅这样的维修办法，让车主很担忧，本来刹车盘的厚度就很薄了，这经过这么一打磨岂不是更不安全了吗？

When Mercedes Benz owners learned of this problem, they quickly asked the repairman how to deal with it? The mechanic took down the brake disc, fixed it on a machine and began to polish it. The maintenance method of the car repairman worries the car owner. The thickness of the brake disc is very thin. Isn't it safer after such polishing?

修车师傅得知奔驰车主的担忧后，向车主解释到，这是在镗盘，只是将刹车盘边缘凸起的部位镗掉，而并非是在对刹车盘厚度打磨，更不会影响到安全问题，奔驰车主听到修车师傅的解释后，这才把心放了下来。

After learning about the concerns of Mercedes Benz owners, the repairman explained to the owners that this was boring the disc, only boring the convex parts at the edge of the brake disc, not grinding the thickness of the brake disc, and it would not affect the safety problem. Mercedes Benz owners relieved themselves after hearing the explanation of the repairman.