Originally Posted by ala_xfire

ELECTRONIC BRAKE PROPORTIONING

Electronic brake proportioning (also called Electronic Brake Distribution or EBD) was introduced a number of years ago, and is now becoming common on many late model import and domestic vehicles. Some applications include late model Honda, Toyota, Audi, Mercedes and others. The Honda Accord was equipped with electronic brake proportioning in 2006, and all Honda vehicles, except the S2000, now have it.

With electronic brake proportioning, pressure from the master cylinder is routed equally to the front and rear brakes. There is no mechanical proportioning valve in the brake system. Instead, the Antilock Brake System (ABS) controls what happens at the rear brakes.

The ABS system monitors the speed of the rear wheels via the wheel speed sensors (WSS) when braking. As long as the rear wheels are slowing at the same rate as the ones up front, and there is no indication that the rear brakes are locking up, full braking force is applied to the rear wheels. With the rear brakes now doing 50% of the work (instead of 20 to 40%), the vehicle stops quicker and in less distance.

On the other hand, if the rear wheels are starting to lock up because the vehicle is braking hard on a wet or slick surface, or because the rear wheels are lightly loaded, the ABS system intervenes to reduce pressure to the rear wheels. This is done by closing solenoids in the ABS hydraulic unit that isolate the rear brake circuits. Other solenoids are then opened to release pressure from those circuits. The solenoids are then repositioned so pressure can be reapplied to the rear brakes.