The laboratory evaluation of brake lining materials at General Motors Engineering Staff is discussed. Physical aspects that may occur during test which were of concern are swell, shrinkage, blistering, extrusion, and sloughing.
The friction materials test machine and test procedures are described. Frictional characteristics considered in the testing are friction level, uniformity of output, shape of family curves, fade, fade and recovery, and resistance to moisture.
Test results are presented in the form of sample plot sheets of good and poor lining performance. Good linings showed fairly uniform coefficient of friction and consistent grouping of the family curves, in contrast to the excessive spread and erratic values of the poor lining example.