Why do the brakes lock up on a 1994 ford Crown Victoria?

Lets say you do not have ABS. If that is the case, is it the front or the back brakes. If it is the back brakes, then it is possible that the brake springs have to be changed, that is of course if you have drum brakes. If you have 4 wheel disk, then its another problem, possible the brake equilizer valve has to be replaced.