The Stovebolt Site Forums The Shop Area Driveline Brake pedal adjustment

'57 3200, just finished an install of front discs, new brake lines and new dual master cylinder / prop valve combo from CPP.

Now that everything is up and functioning - I've got about 3" of 'slop' before the brake pedal meets resistance / engages from the MC. The pedal would have approximately 7" of total travel, from all the way up to the floor - so I'm getting almost half way to the floor before getting any braking action.

I feel like it is possible the push rod that came with the MC is too short - I've backed the rod end off as far as possible, but there is still a too much travel in the pedal before engaging the MC.

Is there another adjustment point I'm missing? Anyone else had a similar issue?

Your master cylinder is probably too small to move enough fluid. You're having to push the M/C piston a long way before it displaces enough fluid to get all the brake parts in firm contact with the drums and discs.. If that's the case, no amount of tinkering with the pedal height will help- - - -you need a master cylinder with a bigger bore. Just because somebody sells you something they claim will work doesn't necessarily mean it will work right. Loose rear brake adjustment can also take up a lot of pedal stroke. Tighten the brake adjuster until you get a firm drag (not locked up) and back off one turn of the adjuster wheel. 10 clicks for manual-adjust brakes, or 20 for the star wheel for self-adjusters.
Jerry

Thanks for your response. It's possible what you are saying is correct (and I for sure needed to tighten up the rear drums, thanks for that advice).

but just so I am clear in what I'm saying the issue is: If I disconnect the push rod from the pedal, and insert it by hand into the MC - I can feel where it "hits home" and actually engages the MC, which would be (I would think) the start of braking action.

When the rod is in that position, the other end of the push rod (linkage end) is at a specific point in space. That is the same point in space the pedal connector point comes to after traveling the approx 3 inches of pedal 'slop'.

So it would seem to me it isn't (yet anyway) a function of not being to move enough fluid, it is either 1) too short a push rod, or I guess possibly 2) the MC or the pedal are in the wrong spot.

What i'm calling 3" of slop travel in the break pedal seems to translate to approx 3/4" of linear travel where the push rod is just floating in air (supported by the rubber boot) not even pushing against the MC piston.

Thanks again -

The slack in the pushrod travel is definitely an issue. You need to fabricate a longer rod, but don't use just any old bolt or all-thread rod except for checking purposes. Most master cylinder pushrods are made of hardened steel so they won't bend during a panic stop. I'd recommend using a Grade 8 bolt like a cylinder head bolt, etc., something that will be tough enough to resist bending when the brakes are applied "vigorously".
Jerry

Terrance 57,
I have a 59 1/2 tn. I recently put a cpp kit for a dual master cylinder on my truck, however I still have 4 wheel drum brakes. The push rod that came with the kit from cpp was to short. I ordered a longer one from them and had to measure twicw cut once to get the fit right.

Thanks fellas - I'll find an appropriate longer rod and move on to tackle the next issue.

Thanks Terrance for starting this thread. I too have a ‘57 3200 with too much pedal travel. I’ve bled them but got no air bubbles. Pedal goes lower than gas pedal and very spongie. Next cool day, I’m checking the push rod and rear drum shoe tightness.

Before I bleed the brakes, I adjust all of the brake shoes so that it takes some effort to turn the wheels. This takes all of the slack out so that the master cylinder has little mechanical work to do moving the shoes very far. Once you get all of the air out, you will end up with a very high, firm pedal.
Then I back off the shoes the number of clicks specified for the truck. This will move your pedal to where it belongs and remain firm.