72 Brake Pedal Travel Adjustment - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rn2fine · 01-07-2011, 03:46 AM

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.

JimKshortstep4x4 · 01-07-2011, 06:38 AM

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

Murphy IRE · 01-07-2011, 11:00 AM

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 ?

JointTech · 05-20-2013, 07:28 PM

Quote:

Originally Posted by JimKshortstep4x4

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.

rn2fine · 01-08-2011, 05:09 PM

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?

CCCC · 01-08-2011, 06:47 PM

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.

Murphy IRE · 01-08-2011, 11:36 PM

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

Lee H · 05-20-2013, 07:41 PM

The factory service manual has a good section on measuring and adjusting the pedal travel, given OEM spec replacement parts are used.
Posted via Mobile Device

domeier · 05-20-2013, 08:49 PM

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.

JointTech · 05-20-2013, 08:52 PM

Quote:

Originally Posted by domeier

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...

68K30 · 05-20-2013, 10:58 PM

You need an "H" gauge, and the instructions to use it.
Posted via Mobile Device

01-07-2011, 03:46 AM	#1
rn2fine Registered User Join Date: Jan 2004 Location: Arizona Posts: 157	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. __________________ 72 C10 Burb 350 700R4 70 C20 LWB 350 Crate TH400 68 Chevelle

01-07-2011, 06:38 AM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	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 __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

01-07-2011, 11:00 AM	#3
Murphy IRE Registered User Join Date: Oct 2009 Location: South Denver Metro, CO Posts: 385	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 ?

01-08-2011, 05:09 PM	#5
rn2fine Registered User Join Date: Jan 2004 Location: Arizona Posts: 157	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? __________________ 72 C10 Burb 350 700R4 70 C20 LWB 350 Crate TH400 68 Chevelle Last edited by rn2fine; 01-08-2011 at 05:10 PM. Reason: Typos

01-08-2011, 06:47 PM	#6
CCCC Registered User Join Date: Mar 2007 Location: San Pedro River, SE Arizona Posts: 735	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. __________________ CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp

01-08-2011, 11:36 PM	#7
Murphy IRE Registered User Join Date: Oct 2009 Location: South Denver Metro, CO Posts: 385	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

05-20-2013, 07:41 PM	#8
Lee H Registered User Join Date: Jun 2010 Location: Upland Ca Posts: 4,149	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. Posted via Mobile Device __________________ 1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703

05-20-2013, 08:49 PM	#9
domeier Registered User Join Date: Sep 2011 Location: San Jose, California Posts: 784	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.

05-20-2013, 10:58 PM	#11
68K30 Registered User Join Date: May 2007 Location: Pennsylvania Posts: 99	Re: 72 Brake Pedal Travel Adjustment You need an "H" gauge, and the instructions to use it. Posted via Mobile Device



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