Good explanation Jim, Here's a question for you. On my 69 Camaro (power front disks, drum rears) I replaced M/C, rear lines and wheel cylinders. I then put new pads all around. When bleeding the rears I could not get pedal to go to the floor, but will on the fronts. Also the rear shoes would not move. I bench bled M/C again, bled the lines at the M/C bleeders, and bled rears and fronts several times. I now get some movement at the rear shoes, but still the pedal won't go to the floor. Could I have "tripped" the proportioning valve by pedal-bleeding the empty rear lines and wheel cylinders? If so how can I re-center it? It seems to have a button covered by a rubber boots on the rear, but I have read different definitions of what that button is for or how to use it, and some people insist that this is NOT a proportioning valve. If your not familiar with Camaros here's what this part looks like: Camaro Camaro Proportioning Valve & Bracket Set, 1967-1969 - Rick's Camaro Parts Any suggestions? Thanks!