The Effect of Cu2S Solid Lubricant Addition, and Varying Density, on the Occurrence of Brake Squeals for One Low-Metal, Organic Type Brake Pad 1999-01-3394

Brake pads with an especially formulated, low-metal organic friction material were tested in a rig especially developed for brake squeal tests. The effect on squeal generation by the addition of 0, 2, 4, 8 and 12 vol% Cu₂S to the friction material was investigated. All tests were performed at low speeds, moderate to low brake pressures and with disc temperatures in the range of 70-270 °C. It was found that the addition of Cu ₂S consistently reduced the number of generated squeals, with an optimum around 4-8 vol% addition. Further, the addition of Cu₂S also lowered the coefficient of friction for the present friction material formulation. A friction minimum was obtained at 8 vol% Cu₂S. Included in this investigation were three sets of pads, all containing 8% Cu₂S, but with different densities. It was found that the pads with the higher density generated fewer squeals than did the pads with the lower density. Within the limits of the test, there was a definite trend for pads with higher friction to generate more brake squeals.