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Old 01-07-2011, 01:46 AM   #1
rn2fine
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72 Brake Pedal Travel Adjustment

On a stock 1972 brake booster and master cylinder setup is there a way to adjust the amount of pedal travel? I think I read somewhere that the rod that comes out of the booster to the master cylinder is adjustable. Just trying to confirm this before I start working on it. Many thanks.
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Old 01-07-2011, 04:38 AM   #2
JimKshortstep4x4
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Re: 72 Brake Pedal Travel Adjustment

It is adjustable but there is a limit as you need to leave enough threads in the rod so that it will hold together. There is a lock nut on the fine threaded rod where it screws together. With the rod installed it is a bit of work to adjust it as getting the shoulder bolt out at the brake pedal is tricky as it hits the steering column. If you look up under the dash by the column you can see the the rod.


Jim
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Old 01-07-2011, 09:00 AM   #3
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Re: 72 Brake Pedal Travel Adjustment

I have another thread out there on "push rod adjustment on 71 K20". As it turned (on my truck) it wasn't the push rod! You'll see the travel distance on mine is OK! It looks like the final problem on mine will be the amount of vacuum. Keep us posted. Measure your pedal travel. What is the problem stiff or soft pedal ?
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Old 01-08-2011, 03:09 PM   #4
rn2fine
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Re: 72 Brake Pedal Travel Adjustment

Thanks Jim.

Murphy IRE - I replaced both the booster and the master cylinder after buying the vehicle and while doing a complete rebuild of it. Vacuum is strong and the pedal travels quite some distance before braking starts. In normal braking the pedal is bottoming out. Periodically I am at the floor and although it is braking it is not braking hard enough. Someone told me that the rod that comes out of the booster is threaded and adjustable. Jim, in his reply to this post yesterday states tha the rod between the pedal and the booster is adjustable. Will follow-up on what Jim suggested today and see if that works. Your thoughts?
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Last edited by rn2fine; 01-08-2011 at 03:10 PM. Reason: Typos
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Old 01-08-2011, 04:47 PM   #5
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Re: 72 Brake Pedal Travel Adjustment

There could be another issue if you replaced the booster and MC, in that there is a shorter non adjustable rod in that linkage (between booster and MC) and those do come in slightly different lengths. If you have the original rod off the truck, might try installing it instead of the one you used. Or, if you re-used the original rod it may not be exactly the correct length for the new booster/MC combo (it could be a bit too short - thus the pedal travel issue) especially if you installed a different type/capacity booster.

I have seen at least three types/shapes of boosters on these trucks - the C10s mostly seem to be all the same (smaller capacity and single diaphragm) - but on C20s and C30s have seen two types (double diaphragm - more effective) and it is among all of these that I think the rod length difference comes ointo play.
The difference in the length of those various rods is not much, but it does not take much difference to have an effect at that point in the linkage.

Don't ask me why this rod issue is so - it has confounded me more than once, and I do not know where one can buy rods of differing lengths. I try to save every one I see in case I need it some day.
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Old 01-08-2011, 09:36 PM   #6
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Re: 72 Brake Pedal Travel Adjustment

Cparman gave some good advice on the push rod. Search the forum using push rod. There were some good threads but i can't remember what they were . I also googled push rod adjustment and then surfed all the various links and articles. Here's the thread:
http://67-72chevytrucks.com/vboard/s...d.php?t=435626
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Old 05-20-2013, 06:28 PM   #7
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Re: 72 Brake Pedal Travel Adjustment

Quote:
Originally Posted by JimKshortstep4x4 View Post
It is adjustable but there is a limit as you need to leave enough threads in the rod so that it will hold together. There is a lock nut on the fine threaded rod where it screws together. With the rod installed it is a bit of work to adjust it as getting the shoulder bolt out at the brake pedal is tricky as it hits the steering column. If you look up under the dash by the column you can see the the rod.


Jim
Argh, that bolt is trying to kill me. I think im going to have to drop the steering column.
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Old 05-20-2013, 06:41 PM   #8
Lee H
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Re: 72 Brake Pedal Travel Adjustment

The factory service manual has a good section on measuring and adjusting the pedal travel, given OEM spec replacement parts are used.
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Old 05-20-2013, 07:49 PM   #9
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Re: 72 Brake Pedal Travel Adjustment

My truck is all stock power brake, 71 k-10, and there is very little pedal travel, maybe an inch max. It moves about 1/2" for normal braking. I wonder if you have air in a line or the master cyl? I replaced the mc some time back, and had to bench bleed the new one twice before it felt right on the truck.
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Old 05-20-2013, 07:52 PM   #10
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Re: 72 Brake Pedal Travel Adjustment

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Originally Posted by domeier View Post
My truck is all stock power brake, 71 k-10, and there is very little pedal travel, maybe an inch max. It moves about 1/2" for normal braking. I wonder if you have air in a line or the master cyl? I replaced the mc some time back, and had to bench bleed the new one twice before it felt right on the truck.
I bench bled the new mc through the prop valve. The whole unit came from CPP with the valve and booster and m/c attached.

Im going to rebleed the brakes. from closest to farthest this time. I did it the other way...
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Old 05-20-2013, 09:58 PM   #11
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Re: 72 Brake Pedal Travel Adjustment

You need an "H" gauge, and the instructions to use it.
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