Does anyone know how much pressure is needed to operate rear disc brakes? I'm going to put a pressure gauge in line to see how much pressure I have going to the rear calipers. I can't seem to get any stopping power on the rear calipers. I used two Wilwood manual master cylinders a 1 inch bore for the front calipers and a 7/8 bore for the rear calipers. Car just won't stop. I used a GM disc brake and caliper kit from Blackbirds Custom on the 9" Ford small bearing rear. I've been working for ever on the brakes and can't get any stopping power at all. I even had it to a brake specialist and spent over $200.00 and he couldn't figure it out. I took the power brakes system off because I couldn't get any pedal at all. Now have a great pedal but won't stop! Any help would be greatly appreciated THANKS!!