Keep in mind the goal is to have the brake bias set very close to the point where all tires would lock at approximately the same time. It is a compromise though as not all speeds and braking zones on a track will be the same. Then some prefer it to be slightly forward or back depending on their driving preference and the situation. A driver with a high downforce, high powered rwd car may prefer the front to lock up slightly before, where perhaps the same driver in a fwd touring car would prefer the rear to lock first. Either way you want to balance front to back to be fairly close to all four locking at the same time in most braking zones. Of course finding that balance may be easier said than done. Just my thoughts anyways.