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Rear disc brake squeal test results confirm the disc wear - brake squeal correlation reported earlier on front disc brakes. A significant amount of Fe transferred from the disc to the NAO pad surface is detected and the distribution of the transferred Fe is very non-uniform on the pad surface. The pad surface formulation reaches that of Low-Steel Lomets. Disc pads from a noisier brake retain more transferred particles than from a less noisy brake. The pad surface retains more transferred Fe after noise test procedures than after performance test procedures. The transferred Fe particles are either barely visible or invisible. During brake noise test procedures, discs wear in weight as much as disc pads. No correlation is found between average in-stop Mu, maximum in-stop Mu or in-stop delta Mu and brake squeal.

Two sets of OE quality brake discs were evaluated for their equivalence in friction and wear under a humidity controlled condition in order to avoid the influence of humidity on friction and wear. These discs were received from two different suppliers located in two different countries. Small differences were found in disc chemistry and microstructure, which resulted in differences in disc properties, and friction and wear characteristics. It is recommended that extreme care must be exercised in determining the performance equivalence of one disc from one supplier against another disc from a second supplier.

Non-Asbestos Organic (NAO) disc pads and Low Steel Lomet disc pads were subjected to high and low humidity conditions to discover how humidity affects these two classes of formulations for physical properties, friction, wear and noise characteristics. The 2 classes of formulations show similarities and differences in response to increasing humidity. The humidity effect on deformation of the surface microstructure of the gray cast iron disc is also investigated. Humidity implications for pad quality control and brake testing are discussed.

Passenger car NAO(Non-Asbestos Organic) disc pads were subjected to low and high humidity conditions. Humidity is found to measurably affect pad dimensions, pad hardness, compressibility, friction, pad wear, disc wear, disc roughness, DTV(Disc Thickness Variation) and brake noise. Also the friction film is found to absorb a significant amount of moisture. It is essential to have a tight control of temperature and humidity for brake testing and quality control if meaningful data are to be generated with minimum variability. Seasonal changes must be considered for brake testing on the road.