Nissan designed the brakes with a heavy front bias, this is to prevent excessive oversteer when people trail-brake into a corner. For people who have developed the habit of braking in a straight line at the track, the heavy front brake bias means the rear brakes are under-utilized. The brake proportioning valve if installed in the front brake lines will allow the driver to reduce bias towards the front, so more of the rear brakes/traction can be used.
