Power Brakes - Pedal Height - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bluec10 · 08-25-2009, 08:31 PM

How far off the floor should the brake pedal be in '69 GMC with power brakes? I'm installing a booster in my truck and in my first attempt the pedal seems too close to the floor and the brake light switch doesn't reach.

oldblue1968chevy · 08-25-2009, 08:52 PM

I went from manual brakes to power disc on my 68 using 72 gmc sierra parts.....my brake pedel is closer to the floor than my clutch...wtf it works but looks funny....i had to adjust brakelite switch also...MAJOR PITA

68gmsee · 08-25-2009, 09:03 PM

Did the same on my trucks and extended the clutch link as far as I dared to. Some guys actually extend the link by adding a section to it.

unclewatts · 08-25-2009, 09:04 PM

Mine isn't like that. I'm wondering if your pushrod that is in the booster is too short. They do come in different lengths. (Actually my brake pedal is higher than my clutch.)

oldblue1968chevy · 08-25-2009, 09:07 PM

oh when i swapped to power brakes i used the power brake rod also.

cparman · 08-25-2009, 09:15 PM

done a bunch of drum/disc conversions. The adjustment under the dash is for pedal height only! If you have a bunch of slop in the pedal before the brakes engage, you have too much clearence between the booster/master. It does not take much between these to to have a BUNCH of slop 1/4" is a ton. Most kits for our trucks, also tell you to drill a hole about 1" lower that where the manual brake hole is. Do this, and then adjust the rod until the brake pedal is where it was before you started working on it. Mine is exactly where it was when the General built it, and if you do not pay attention ( sometimes I don't ) it will darn near throw you thru the windshield! I believe, that if you go to the tech pages on CPP ( I have never used their stuff ) that it will repeat what I have just said.

bluec10 · 08-25-2009, 11:04 PM

Just got the truck going. The push rod is adjustable, so I set the height a bit lower than the clutch. I just drove it, though, and I think a bit lower is better because when you raise your leg that high to step on the brake you tend to step on it too hard. Setting the brake light switch is a major pita!

Longhorn Man · 08-25-2009, 11:20 PM

that is the exact reason the pedal is supposed to be lower. There is supposed to be 2 holes on the pedal arm for the pushrod. One is for manual, one for power.

bluec10 · 08-25-2009, 11:23 PM

I heard that, but mine only has the one.

oldblue1968chevy · 08-26-2009, 04:48 PM

need to check that then.........

cparman · 08-26-2009, 05:39 PM

most aftermarket kits that have instructions that are worth a crap , will tell you to drill a hole in the brake pedal about 1" lower than the manual hole. This changes the fulcrum point??? If I said that right. Like Longhorn man said, IF you had a hole an inch lower in your pedal, and had MANUAL BRAKES, I bet it would be a bear to stop. With power brakes, a hole a bit lower, changes the fulcrum, to " tune " the brake pedal to the power assist.

mclairmo · 08-26-2009, 06:40 PM

With manual brakes the upper hole is used to increase the amount of leverage that the pedal exerts upon the push rod. Power brakes require less "leverage" due to the power assist and thus, require the use of the lower hole. If you use the upper hole and a power booster, you may have very sensitive brakes that grab too easily and are hard to modulate.

npoe2982 · 03-15-2012, 10:55 PM

i found that adjusting the push rod is a bad idea if the only issue is pedal height. when you install the mc you want the mounting to the booster to sit flush with no pressure on the mc. if you have pressure on the mc you will pressurize your system leading to the brakes having pressure with no return of pressure. essentially the breaks will lock out and will not allow pressure to return to the mc, you will burn your brakes, end of sentence. adjusting the pedal is a pain but i would say much better than the alternative. easiest way is the unbolt the column from the dash, loosen the bolt from the treaded rod attached to the pedal and adjust the pedal height that way before adjusting the push rod. i hope this will be helpful. adjust the push rod was a major mistake for me.

08-25-2009, 08:31 PM	#1
bluec10 Registered User Join Date: Apr 2002 Location: Manitoba, Canada Posts: 663	Power Brakes - Pedal Height How far off the floor should the brake pedal be in '69 GMC with power brakes? I'm installing a booster in my truck and in my first attempt the pedal seems too close to the floor and the brake light switch doesn't reach. __________________ Present: 2015 Tacoma. Yeah, not a GM, but I love it. 1969 GMC 32,000 - fix, drive, relax, fix... 2019 BMW R1250 GSA - Yahoooooooo 1979 Honda GL 1000 - retro touring at its best. Past: '05 Sierra 4x4 - Had 270,000 KM and running well when it was written-off by a stop sign runner. '94 F-150 from the "F word" company. I'll admit it...good truck. Sold what was left of it for $800 to a guy who came to pick it up at 11:00 PM with cash in hand. Hmm. '79 Sierra Grande (Black) organ donor - perfect rebuildable 4-bolt 350 and a good TH350. '76 Sierra Grande (Orange) - hate isn't too strong a word. Kid who bought it turned it into a hot rod. '68 C-10 R.I.P. - Dad's old truck...too far gone to resurrect. '59 C-50 - with hoist. Truck is gone, wife isn't. Nuff said.

08-25-2009, 08:52 PM	#2
oldblue1968chevy Grandpa in the rustmobile... Join Date: Nov 2008 Location: Spokane WA/Viola TN Posts: 11,422	Re: Power Brakes - Pedal Height I went from manual brakes to power disc on my 68 using 72 gmc sierra parts.....my brake pedel is closer to the floor than my clutch...wtf it works but looks funny....i had to adjust brakelite switch also...MAJOR PITA __________________ John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4

08-25-2009, 09:03 PM	#3
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Power Brakes - Pedal Height Did the same on my trucks and extended the clutch link as far as I dared to. Some guys actually extend the link by adding a section to it. Last edited by 68gmsee; 08-25-2009 at 09:03 PM.

08-25-2009, 09:04 PM	#4
unclewatts 70 Chevrolet=Obsession Join Date: Jun 2009 Location: nice ca Posts: 1,067	Re: Power Brakes - Pedal Height Mine isn't like that. I'm wondering if your pushrod that is in the booster is too short. They do come in different lengths. (Actually my brake pedal is higher than my clutch.) __________________ I'm Just like my truck. Old, Ugly and Grouchy. Except my truck starts easily in the morning and doesn't smoke! IT'S NOT EASY BEING GREEN! -Kermit the frog 1970 Chevrolet C-10 Longbed Stepside : 350, Muncie M20, 3.08 GM corp. positraction Forest green exterior/light green interior(Where all my money goes) 1996 Toyota Corolla (Parts runner)

08-25-2009, 09:07 PM	#5
oldblue1968chevy Grandpa in the rustmobile... Join Date: Nov 2008 Location: Spokane WA/Viola TN Posts: 11,422	Re: Power Brakes - Pedal Height oh when i swapped to power brakes i used the power brake rod also. __________________ John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4

08-25-2009, 09:15 PM	#6
cparman sharp as a marble Join Date: Jan 2007 Location: atlantic beach,florida Posts: 1,082	Re: Power Brakes - Pedal Height done a bunch of drum/disc conversions. The adjustment under the dash is for pedal height only! If you have a bunch of slop in the pedal before the brakes engage, you have too much clearence between the booster/master. It does not take much between these to to have a BUNCH of slop 1/4" is a ton. Most kits for our trucks, also tell you to drill a hole about 1" lower that where the manual brake hole is. Do this, and then adjust the rod until the brake pedal is where it was before you started working on it. Mine is exactly where it was when the General built it, and if you do not pay attention ( sometimes I don't ) it will darn near throw you thru the windshield! I believe, that if you go to the tech pages on CPP ( I have never used their stuff ) that it will repeat what I have just said.

08-25-2009, 11:04 PM	#7
bluec10 Registered User Join Date: Apr 2002 Location: Manitoba, Canada Posts: 663	Re: Power Brakes - Pedal Height Just got the truck going. The push rod is adjustable, so I set the height a bit lower than the clutch. I just drove it, though, and I think a bit lower is better because when you raise your leg that high to step on the brake you tend to step on it too hard. Setting the brake light switch is a major pita! __________________ Present: 2015 Tacoma. Yeah, not a GM, but I love it. 1969 GMC 32,000 - fix, drive, relax, fix... 2019 BMW R1250 GSA - Yahoooooooo 1979 Honda GL 1000 - retro touring at its best. Past: '05 Sierra 4x4 - Had 270,000 KM and running well when it was written-off by a stop sign runner. '94 F-150 from the "F word" company. I'll admit it...good truck. Sold what was left of it for $800 to a guy who came to pick it up at 11:00 PM with cash in hand. Hmm. '79 Sierra Grande (Black) organ donor - perfect rebuildable 4-bolt 350 and a good TH350. '76 Sierra Grande (Orange) - hate isn't too strong a word. Kid who bought it turned it into a hot rod. '68 C-10 R.I.P. - Dad's old truck...too far gone to resurrect. '59 C-50 - with hoist. Truck is gone, wife isn't. Nuff said.

08-25-2009, 11:20 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: Power Brakes - Pedal Height that is the exact reason the pedal is supposed to be lower. There is supposed to be 2 holes on the pedal arm for the pushrod. One is for manual, one for power.

08-25-2009, 11:23 PM	#9
bluec10 Registered User Join Date: Apr 2002 Location: Manitoba, Canada Posts: 663	Re: Power Brakes - Pedal Height I heard that, but mine only has the one. __________________ Present: 2015 Tacoma. Yeah, not a GM, but I love it. 1969 GMC 32,000 - fix, drive, relax, fix... 2019 BMW R1250 GSA - Yahoooooooo 1979 Honda GL 1000 - retro touring at its best. Past: '05 Sierra 4x4 - Had 270,000 KM and running well when it was written-off by a stop sign runner. '94 F-150 from the "F word" company. I'll admit it...good truck. Sold what was left of it for $800 to a guy who came to pick it up at 11:00 PM with cash in hand. Hmm. '79 Sierra Grande (Black) organ donor - perfect rebuildable 4-bolt 350 and a good TH350. '76 Sierra Grande (Orange) - hate isn't too strong a word. Kid who bought it turned it into a hot rod. '68 C-10 R.I.P. - Dad's old truck...too far gone to resurrect. '59 C-50 - with hoist. Truck is gone, wife isn't. Nuff said.

08-26-2009, 04:48 PM	#10
oldblue1968chevy Grandpa in the rustmobile... Join Date: Nov 2008 Location: Spokane WA/Viola TN Posts: 11,422	Re: Power Brakes - Pedal Height need to check that then......... __________________ John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4

08-26-2009, 05:39 PM	#11
cparman sharp as a marble Join Date: Jan 2007 Location: atlantic beach,florida Posts: 1,082	Re: Power Brakes - Pedal Height most aftermarket kits that have instructions that are worth a crap , will tell you to drill a hole in the brake pedal about 1" lower than the manual hole. This changes the fulcrum point??? If I said that right. Like Longhorn man said, IF you had a hole an inch lower in your pedal, and had MANUAL BRAKES, I bet it would be a bear to stop. With power brakes, a hole a bit lower, changes the fulcrum, to " tune " the brake pedal to the power assist.

08-26-2009, 06:40 PM	#12
mclairmo Registered User Join Date: Jan 2006 Location: Take Off Posts: 1,908	Re: Power Brakes - Pedal Height With manual brakes the upper hole is used to increase the amount of leverage that the pedal exerts upon the push rod. Power brakes require less "leverage" due to the power assist and thus, require the use of the lower hole. If you use the upper hole and a power booster, you may have very sensitive brakes that grab too easily and are hard to modulate.

03-15-2012, 10:55 PM	#13
npoe2982 Registered User Join Date: Mar 2012 Location: wichita Posts: 7	Re: Power Brakes - Pedal Height i found that adjusting the push rod is a bad idea if the only issue is pedal height. when you install the mc you want the mounting to the booster to sit flush with no pressure on the mc. if you have pressure on the mc you will pressurize your system leading to the brakes having pressure with no return of pressure. essentially the breaks will lock out and will not allow pressure to return to the mc, you will burn your brakes, end of sentence. adjusting the pedal is a pain but i would say much better than the alternative. easiest way is the unbolt the column from the dash, loosen the bolt from the treaded rod attached to the pedal and adjust the pedal height that way before adjusting the push rod. i hope this will be helpful. adjust the push rod was a major mistake for me.



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