[Christ]

Originally Posted by wdb

(Tire pressure quoted for next comment.) That all assumes that you are stopping in a straight line on a smooth road. That is not often the case in normal situations, let alone emergencies.

No, it assumes I'm driving an unloaded truck. In turns and emergency scenario braking, you lose even more of your rear braking power when driving unloaded, because you're more likely to make the rear end slide when braking heavily. This is the point of Ford's RABS (rear ABS) system, to prevent lockup of both rear tires (one solenoid controls both rear tires on the same line, PITA setup that I fully plan on removing).

IIRC, the actual braking force on several trucks is set so that only something like 30% of the usable pressure of the master cylinder is transmitted to the rear brakes, and the brakes themselves are larger in the rear so that even less PSI is transferred from the wheel cylinders to the drums to help prevent this scenario.