Question for guys with stock power brakes

[chipflyer]

This is for you guys with c-10 71-72 trucks with original power brakes. How much free travel do you have before your brakes actually start to stop your truck? Is it less than an inch? It seem like mine with a new master cylinder and booster drops between 2 and 3 inches, I am used to it but my dad drove it today and said he thinks the pedal goes down way to far. I am wondering just how much free travel it should have?

Thanks
Jeff

[70C10Toejam]

From my Haynes manual, convers '67-'87:

test with brakes cold.
measure distance from pedal to floor.
with power brakes, pump pedal at least 3 times WITHOUT starting engine.
press firmly on the pedal and measure again.
the distance of travel should not exceed 4 1/2 inches for power brakes. (3 1/2 for manual)

it does not differentiate between drums or disk.

[truckdude239]

i like mine in all my cars and trucks between 1 inch to 1 1/2 inch never had any trouble

[Longhorn Man]

The way I've always done it;
Start off with a cold system. No driving at all for 5 hrs is MY standard... NFC what the *book* would call it.
Adjust the drums (either with disk/drum, or drum/drum) to where they lightly rub.... more of a slight scuff, when the wheel is rolled while jacked up.
Then check the pedal with a drive around the block.
Pull the truck back in, pump the brakes (engine off) till all the vac is gone, then, by hand, depress the pedal and feel for the free play. I think the correct play at the pedal is 1/2 inch to 3/4 inch. (honestly, i do it by feel) If the free travel is more than that, then you remove the master cylinder from the booster (no need to undo the lines, just the 2 9/16 *wrench size* nuts)
Pull the pushrod out of the booster.
Measure this rod to a 16th of an inch.
The end with the acorn nut is adjustable. I normally start by threading it out all the way, and running it on a wire wheel, or a sand blaster is you have access. Then i coat the thread with anti-seize compound.
Adjust it back in to what it was when you pulled it out.
Now, turn it 1/2 turn longer than it was, install the rod and the master cylinder, and recheck the free travel. You'll need to tighten the nuts holding the booster, any loosness will show up as free travel.
You may do this more than a few times, however, small incriments is what you want.
You NEED the free travel, theings expand when they get hot, and your rear brakes WILL drag if you don't have enough free travel.
once you have it all adjusted to what you think is good, pop off the hub caps (if aplicable) and go for a 10 mile freeway drive. *take that 9/16's wrench with you) Stop a few times, and CAREFULLY check the temperature of the rear wheel from time to time with the BACK of your hand... not the palm. Common sence will tell you what is warm, and what is hotter than h*ll.

Like I said, i dunno what the book calls for, but this is how I've adjusted all my trucks for over a decade now, and have never had any problems... that, and i kinda do it by feel.
And on that first test drive, get a feel for them in the neighborhood first... otherwise, you'll kiss the steering wheel when you jab them at what you consider normal for your truck.