Thread: Brakes

Tweet

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!!

Not so much a matter of how much pressure, but the percentage of pressure that is going to the rear.... I usually start with about 40% on the rear, then tweak it in with the proportioning valve after that with a single master cylinder....... With dual master cylinders, start by checking the pressure at the master cylinders, then work from there with the bias adjustment to increase the rear pressure.... Are your rears the big or metric GM calipers??? The big one's also take a ton of fluid to work and depending on your pressure at the rear, could even need a bigger master cylinder.... I usually go with equal sized cylinders and work it out with the bias adjuster and pressure gauges....

Thanks! The rear calipers that came in the kit are 75 Chevy 3/4 ton 4X4 front calipers and rotors.

Yup, that's the big one's.... What size are your front's? The big calipers are going to take a bunch of pressure to get applied, might want to start at about even front and rear pressure.....if the front calipers are smaller, I believe this is going to be your problem... I usually use the smaller metric calipers on the rear.....Curious to hear what your brake pressures are...if you have the correct adapter, checking the brake pressure at the bleeder valve is going to be the most reliable test....

Early Chevy Monte Carlo calipers on front. I have to wait until tomorrow to find a press gauge to use. Then I can check them.