A method for determining a performance parameter of a brake with a first (311) and a second (313) brake element can be made to interact to generate a friction force (F.sub.R) and a friction torque (N.sub.R), a first set (204a, 204b) of friction coefficients (.mu.) being determined between the first (311) and the second (313) brake element in the field, the first set (204a, 204b) of friction coefficients (.mu.) being compared with a predetermined second set (204) of friction coefficients (.mu.), and the performance parameter being determined based on a deviation of the first (204a, 204b) and second set (204), the deviation being obtained from the comparison.