Divergence of Thickness Losses and Weight Losses of Disc Pads for Passenger Cars: High-Copper NAOs and Copper-Free Low Mets

The current investigation was undertaken to find out if lighter-weight passenger car disc pads would exhibit wear behaviors similar to pickup truck pads and commercial heavy truck drum linings in terms of the permanent volume expansion of the friction material contact surface region. 2 high-copper Non-Asbestos Organic formulations and 3 copper-free Low-Met formulations were tested according to the SAE J2522 test procedure. In all cases, the measured pad thickness loss was found to be less than the thickness loss calculated from the weight loss, indicating pad volume expansion, in full agreement with the results from the pickup truck and heavy trucks. One needs to consider pad property changes associated with the volume expansion if good correlations are to be found between pad properties and brake friction, wear and NVH.