See the thickness: a new brake pad thickness is generally around 1.5cm, with the use of continuous friction will gradually thinning the thickness. When the thickness of the brake pad has been observed only about 1/3 of the thickness (about 0.5cm) or so. The owner will increase the frequency of self-test, ready to replace the. There are individual models due to wheel design reasons, do not have the conditions to see the naked eye, you need to remove the tire to complete.
If it is the latter, wait until the warning light is on, the brake pad metal base and the brake disc are already in the iron mill state, this time, in the tire near the edge of the rim to see the bright iron. Therefore, we recommend that you regularly check the wear of the brake pad to see if it can be used, and do not just believe the warning light.