Rear and Front Connection
Hear is an article from Mark Allen. It tackles the importance of having the rear and front brakes to work together for efficiency
Q. I purchased a new Olds Intrigue in September 1998. The left rear brake rotor had a visible rust scale ring around the exterior about one-quarter-inch wide, roughly in the center of the swept area. I figured it would be worn away with brake usage. After 98,000 miles on the vehicle, it hasn’t gone away. The rear rotors are not even shiny and the original rear brake pads show very little wear. My wife and I are not very hard on brakes; we replaced the front pads for the first time at 86,000 miles.
Is there a proportioning valve between the front and rear systems that should be replaced?
A. Obviously, the rear brakes on your Olds aren’t doing their share of the work or the rear discs would be as shiny and rust-free as the fronts. The proportioning between the front and rear brakes is achieved by the varying diameters of the pistons in the respective calipers, and (in some vehicles) by a separate proportioning valve. Other vehicles also use a check valve that maintains a minimum pressure in the rear brake lines to reduce pedal travel.
If there isn’t a pound or two of residual pressure in the lines, the rear pads will work their way back into the brake calipers a few thousandths of an inch because of normal brake disc run-out. If so, most of your initial brake pedal travel just gets the pads back to where they belong. The check valves in your car are inside the master cylinder. You car has enough mileage on it to justify replacing the entire master cylinder.