Why are there grooves in the brake disc?
There is a simple reason. The grooves are made of brake pads. Brake pads and discs are flat from a macro perspective, but their surfaces are not flat from a micro perspective. In the process of making brake pads, some metal fibers should be mixed inside, and all kinds of substances are evenly distributed inside the brake pads after mixing. Therefore, the friction coefficient at any position on the brake pad is not necessarily the same. Therefore, it is inevitable that the amount of wear in different parts will be different when braking. So when braking, with the rotation of the brake disc, many concentric circles will be left on the brake disc. Like sandpaper.
Normal brake disc groove is not obvious, it looks more like fine lines, and there is no particularly obvious concave and convex feeling when touched by hand. This is a normal phenomenon and does not require special treatment. For example, the brake disc in the above picture can clearly see that there are many subtle traces on its surface, but this is a normal phenomenon. Many brake discs on the road are like this, don't worry.
However, some brake disc wear grooves are particularly deep, and some are particularly wide, which have obvious concave-convex feeling when touched by hand, and belong to abnormal wear. Sometimes sand or other hard particles enter between the brake disc and the brake pad, which will also lead to local excessive wear. Or there is something wrong with the quality of the brake pad itself, and there are large hard particles inside, which will also lead to abnormal wear of the brake disc. For example, a wide and deep ditch like the one above is abnormal wear.
There is also the picture above, which belongs to the serious trough. You can see that there are many grooves, all of which are very wide and deep. Obviously, it is impossible for normal brake pads to grind brake discs like this.
Harm of brake disc groove
If it is the first case, there is no need to worry about the slight groove, and it will not have any impact. Because this is a normal phenomenon of friction between brake pads and brake discs.
If it is a deep and wide groove, it will have an impact. Because the groove part is always deeper than the normal part, the brake pad will be scrapped in advance, and even the strength of the brake pad will be affected. And the deeper the ditch, the greater the impact. Just like the barrel effect, it is the shortest plate that determines the water volume of the barrel, and it is also the most worn part that determines the life of the brake disc.
How to deal with abnormal groove of brake disc
The first method is to smooth the surface of the brake disc with a lathe and turn it into a new plane. The usual practice is to use a special brake disc polisher, install the corresponding wheel hub on its spindle, install and tighten the brake disc according to the position of the screw hole, then start the machine and cut off the metal on the surface of the brake disc with an alloy blade.
In the past, people used to put it on ordinary lathes, which tested the master's skills. If the chuck is biased, it is easy to skew the plane of the brake disc, so that although the surface looks flat, its datum plane has deviated. After installing this kind of brake disc, you will feel terrible when you step on the brake. This also requires a lot of brakes.
Although the effect of brake disc polishing is very good, not all dents are suitable for use.
Generally speaking, brake discs with many grooves are suitable for this method. For example, the brake disc in the above picture has too many grooves to count and can only be flattened on the machine. I can't tell you anything, just cut it off.
However, if the grooves are few and deep, it is not suitable to use the lamp method, because the lamp needs to cut off the brake disc in the normal position until it is flush with the lowest part of the groove. If the groove is deep, it will be cut off a lot. As a result, you flattened the brake disc, so it's probably time to change it. Therefore, for this kind of brake disc with few grooves, the best way is to polish the brake pads.
Because the surface of the brake pad is uneven after the groove appears in the brake disc, the position corresponding to the groove will definitely be higher than other places. There will be raised edges, and when braking, the plane of the brake pad will contact the plane of the brake disc to generate friction. The edge of the brake pad is embedded in the groove of the brake disc, and there is friction. The wear rate of these two parts is the same, because the materials are the same. Therefore, the groove will not disappear basically after it appears, and it will deepen with the wear of the brake pad. If the brake pad is removed at this time and the edge of the brake pad is ground flat, there will be no friction in the groove when the brake is used again, and the groove will certainly not deepen without friction. After a period of use, the groove will flatten with the wear of the brake disc.
The grinding method is simple. After removing the brake pad, grind off the raised edge with fine sandpaper and smooth the surface of the brake pad. However, it should be noted here that this part of the brake pad corresponding to the groove will not be rubbed when stepping on the brake after grinding, so after a period of use, there will be an edge in this place, which needs to be removed and polished regularly.
However, there is also a way to save trouble, that is, not only to smooth the edge of the brake pad, but also to grind a groove slightly deeper than the groove on the brake disc. This can prevent the brake pads from bulging again. When the groove on the brake pad is ground flat, the groove on the brake disc is almost ground flat, and the two surfaces are closely attached. At that time, there were two grooves on the left front wheel of my car. I ground two grooves at the corresponding places of the brake pads and put them back. Later, I forgot about it. About a year. When I went to see it again, the brake disc was shiny and the groove was long gone.
Some friends may be worried. If the brake pad is polished flat, or even a groove is ground, will it affect the braking performance? In fact, according to my personal experience, it has no impact at all. Because the groove actually occupies a small area, and the braking force of the braking system is also sufficient. The easiest way to judge is to try to brake suddenly after grinding. If you can step on ABS, it means that the brakes are not affected.
The slotted brake disc also has a certain relationship with driving habits. If you can notice these points, the probability of serious grooves on the brake disc should be much lower:
1, don't slam the brakes unless there is an emergency.
Braking force is a linear thing, that is to say, the driver can choose the appropriate pedaling force according to the demand for braking strength. But under the feet of some drivers, the brake pedal seems to have only two States: stepping to death or not stepping. No matter what the situation is, as long as the brakes are bound to slam, they will be annoyed. In this way, slamming on the brake disc and brake pad will suddenly contact the force, which is easy to cause abnormal wear.
2. Avoid continuous braking for a long time.
Have you ever encountered such a situation: on the road of continuous downhill, some cars can light up all the way. They don't use the power of the engine mechanism to control the speed, but only step on the brakes to control the speed, so that stepping on the brakes for a long time will make the brake disc and brake pad produce high temperature. High temperature is easy to sinter some substances in the brake pad, thus forming some hard spots. The hardness of these hard spots is much higher than that of brake pads. In this way, the other parts of the brake pad wear a little when you step on the brake, but the hard point is hard enough to be ground down, and it is easy to grind the brake disc out of the groove.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.