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Old 10-20-2011, 08:14 AM
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Originally Posted by oldguy829
learned a little trivia, for Studebakers anyway. The pushrod has to be adjusted to near zero play. I guess it's a combination of pedal length, pushrod length, and MC size, any play and it just doesn't engage the brakes. 1/4 inch of adjustment the the difference was amazing.
What you have found is correct and is not just for Studebaker's but all master cylinders.

The play from the end of the pushrod to the bottom of the hole in the master cylinder piston should be set at the minimum amount required to insure that the piston fully returns when the brake pedal has been released.

Depending on the pedal ratio, 1/8" clearance at the end of the pushrod could easily be over an inch of travel at the pedal BEFORE the master cylinder piston even begins to move. This could result in running out of pedal travel before the piston in the master cylinder has traveled far enough to fully apply the brakes.

The master cylinder piston diameter and travel also need to be of sufficient size to allow the wheel cylinders/calipers to be able to move enough to enable the shoes/pads to have good contact with the drums/rotors and have sufficient applied pressure to stop the rotational forces. i.e. Master cylinders designed for drum brakes often do not have sufficient capacity to fully operate disc brake calipers.
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