A disc brake is one of important auto parts for automotive industry which effected directly to life safety. The wear of brake rotor war affected to the brake efficiency. Lf the wear of rotor was discovered while operating the risk of accident shall be reduced. Therefore a study of disc wear affected to brake distance was the one of alternative for the brake efficiency testing. From this reason the aim of project is to test brake efficiency from the wear of brake rotor with the experiment conditions from JASO C 406 [1]. By the test conditions are focused on 3 cases of the wear: rotor little roughness rotor and abundant roughness rotor. The conditions of experiment consist of 100 200 และ 3000C on the rotor surface operating pressure 2 4 and 6 MPa initial speed before brake applied 50 and 80 km/hr. Based on the result of experiment was revealed that the braking distance deceleration and the brake ability with deceleration per unit of area. The result of experiment shown that the ordinary rotor at 6 MPa 300 0C and 50 km/hr. is given to the shortest of braking distance 69.7 m. Although the average of deceleration and the brake ability is take up on little roughness rotor. In case of the longest braking distance was occurred on the abundant roughness rotor. However from this study is discovered to the high temperature and the high pressure is significant to the braking distance shortened.

Admittedly a disc brake plays an important role in the auto part industry since it concerns directly with safety. Therefore the wide range of disc brake has been designed in order to develop its heat ventilation. Thus this project has designed a back-vented brake disc which is difference the current one (front-vented) and tried to create the test to find out the temperature diffusion of the disc brake with the hope to evaluate the coefficient of the heat convection varied by the temperature changing in both kinds of brakes under the forced heat convection in the steady condition. However the steady heat conduction and radiation value will not be counted because it is insignificant. The JASO C406: 2000 Standard is adopted as a guideline in the test. The outcome coefficient of heat conduction will be used in the simulation via the Finite Element Method (FEM) in order to study the temperature diffusion and heat ventilation of both kinds of brakes at each temperature level. Consequently the experimental work reveals then the heat convection coefficients of both kinds are unidirectional. The heat convection coefficient of the front-vented disc brake is 4.40 % in average higher than that of the back-vented disc brake. From the simulation the front-vented disc brake can ventilate the heat better than the back-vented disc brake at 3.02 % in average. It can be summarized that the front-vented disc brake has more temperature difference than the back-vented disc brake. Hence the front-vented disc brake likely gets more stress from the temperature than the back-vented disc brake and might be damaged during the operation more than the another type. Therefore this is tendency that the back-vented is safer than the front-vented brake disc for usage.