Brake pedal and booster pin setup specs

[davepl]

New Booster, new Master, reinstalling pedal assembly. 1972 3/4 ton front discs.

All new parts, so I need to set them up. I could not find a spec or even steps in the shop or assembly manual, so maybe they just assume new parts are in spec. In fact, I don't see a way to adjust the pin depth out of the master anyway.

Here's what I did, maybe someone can spot an error or tell me the right way!

- I set the pedal height (while connected to booster and linkage) so that it's about 1/4 to 1/2" lower than it would be if free. This is to ensure the pedal can come all the way out (and not drag the brakes, for example).

To check the booster pin to master clearance, I just measured with a depth micrometer. Here's what I found:

- The pin is recessed into the booster by 0.25" from the mounting surface
- The receiver is recessed is 0.50" into the master cylinder rear bore stand
- That stand itself is 0.59"

So, I've got 0.75" less the 0.59, which is 0.16" between the pin and the master cylinder.

Good enough that I've got a gap, which is required, but how much is the right amount?

[mgchevyparts]

Originally Posted by davepl

New Booster, new Master, reinstalling pedal assembly. 1972 3/4 ton front discs.

All new parts, so I need to set them up. I could not find a spec or even steps in the shop or assembly manual, so maybe they just assume new parts are in spec. In fact, I don't see a way to adjust the pin depth out of the master anyway.

Here's what I did, maybe someone can spot an error or tell me the right way!

- I set the pedal height (while connected to booster and linkage) so that it's about 1/4 to 1/2" lower than it would be if free. This is to ensure the pedal can come all the way out (and not drag the brakes, for example).

To check the booster pin to master clearance, I just measured with a depth micrometer. Here's what I found:

- The pin is recessed into the booster by 0.25" from the mounting surface
- The receiver is recessed is 0.50" into the master cylinder rear bore stand
- That stand itself is 0.59"

So, I've got 0.75" less the 0.59, which is 0.16" between the pin and the master cylinder.

Good enough that I've got a gap, which is required, but how much is the right amount?

.030 is the spec for pin to master clearance. As long as you have a "gap" and the pin isn't touching you're good. Your clearance is excessive but you'll be OK, I wouldn't trust your measurement method. There is a special "H" frame simple device to accurately measure this. I bought the "H" ool years ago from Master Power Brakes for around $15.00, at least I think it was them that I bought one years ago.