The biggest wear limit in theory: the brake disc is not 2 mm, use to limit must be replaced after new brake discs. But in actual use, the owner of the big department did not strictly enforce the standards, change the frequency to driving habits to measure according to oneself, roughly measures are as follows:

Low brake pad replacement frequency, if change frequency is high, so suggest how to check the thickness of the brake disc, after all, you piece of fee is faster that you brake with a lot of, so you need to regularly check the brake disc.

Low to decide according to wear: because the brake disc in addition to normal wear and tear, and because of the quality of the brake pad or brake discs and erosion wear in the process of normal use, if the brake disc is a foreign body wear out some more deep groove, or disk wear deviation (thin in some places, and in some places thicker) is suggested to replace, because this kind of biased wear after will directly affect the safe driving.