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kenrodp 11-21-2001 06:18 PM

proportioningg valve adjustment
How do you adjust the proporting valve on a brake system? I have a 47 Chevy with disc brakes in the front, rear drum, it has a knob on the valve, What is the rule of thumb for adjusting it. It has a frame mounted master cylinder with a power booster but it is not sensitive at all to braking, I really have to push hard for stopping.

KULTULZ 11-22-2001 03:01 AM

-Brake Trouble Shooting Guide-

courtesy of Master Power Brakes

First you need to determine the cause of the hard brake pedal.

Some can fairly well set the brake bias by feel, but a set of pressure gauges is the correct way followed by a session on a skid pad (large abandoned parking lot following a hard rain).

Let us know what you find-you may well help someone else :D

Phat 11-24-2001 09:31 AM

Kenrodp the propostioning valve will have nothing to do with brake pedal pressure(hard/soft pedal)(I hope you have it plumbed to the rear brakes?? it just stops rear lock up and we seldom even use them) You need to measure the the pedal itself from the pedal pad to the shaft that holds it to the frame. Now measure the point that the mastercyl bolts to the arm up/down to the shaft, divide that number and you should come up with something around 6 to 1. If its 4 to 1(or less) it will really be hard to stop no matter what you do for a booster or cyl. Also if its in the 8 to 1 or higher you will have a long throw on the pedal(not good) Make sure te master is about 1 inch diam piston(now thats a guess /starting point. Also 3/16 lines on the disc(AN3 if braided)Give some more info on the rest of the braking system Like booster size what caliper your using ,line size to the rear and front.

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