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#1 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Short version: Has anyone had a brake issue created or resolved by adjusting the pedal angle via the clevis?
Not my blue truck, but I've had a brake problem for 10 years. No one has ever been able to solve it. Everything has been replaced and rebuilt and the problem remains... so where does it hide? Here's the problem: you cannot panic brake. If you attempt to, the pedal responds but slowly. So about 1/2 second later you get full braking which is more than adequate. So braking is powerful, but slow to respond. This started when I first added rear discs from a Master Power kit, but I'd also upgraded fronts and master at the same time. So the last time it responded well was drum brakes. I have this same vehicle in a factory disc-drum setup and that's all I want, it to respond as well as the stock one I have! Here's just a bit of what I've done: I replaced the master. I replaced the booster. I tried a Hydraboost for more assist. Various different pad materials for different grips. I had the car fully restored, all new lines and distribution blocks, etc. It still remained! So since everything was now new and the problem remained, I threw in the towel and put a full four-wheel Wilwood disc brake setup on it. Everything from the booster to the rotors is Wilwood. Same problem. After 10 years of trying everything and 5 shops and no ideas, I just gave up and don't really drive it. But I'd still like to fix it. Then this month I was reading a magazine tech article about a guy describing the same thing, who's done all the same things, and he's concluded then that since he's replaced everything, and describing the same slow-to-respond problem, that it can only be in the pedal adjustment because that's all that's left! The magazine response wasn't helpful, but someone else had the same problem. The brake pedal is adjusted to be about as high as the clutch pedal right now. Before I try to change it though, here's my question: Has anyone had a brake issue created or resolved by adjusting the pedal angle via the clevis? That's really my question for today!
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#2 |
Who Changed This?
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Location: Simi Valley, CA
Posts: 10,430
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Did it have power brakes before you made the upgrades? Manual versus power brakes mount the push rod on different locations on the brake pedal lever.
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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#3 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
It was power before and after, thanks!
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#4 |
Who Changed This?
![]() Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,430
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Mine was power before I went to disc brakes. The pedal was as hard as a rock after I installed the disc brakes. In my case, the booster had been damaged in shipping. Is the other vehicle a truck?
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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#5 |
Senior Member
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Location: Godley, TX
Posts: 17,964
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
On the brake pedal lever - in which hole is your pushrod clevis? (upper or lower)
I believe power should be the upper location - and, while you shouldn’t have to change it if you went from a power setup to a power setup, if it’s always been bad, then perhaps it’s always been in the wrong hole. Probably not the issue, but just a thought. I would have guessed it was the booster, but sure sounds like you’ve eliminated that as a possibility several times. |
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#6 |
Registered User
![]() Join Date: Nov 2005
Location: Los Angeles, Ca
Posts: 135
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Very interested as I have this exact problem with the exact same symptoms. I have stock front disks from a 71-72, new corvette master and dual 9” booster, all new hard and flex lines, new rear disks/pads with parking brake, wilwood adjustable prop valve, new front bearings.
I’ve bled this thing many times using the pedal method, vacuum, and tried pressure bleeding as well.
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1968 Chev SWB Fleet with GMC Clip and lots of 71-72 parts! |
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#7 |
At the body shop.
Join Date: Aug 2009
Location: Land of fruits and nuts.
Posts: 5,218
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Residual pressure valves.
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" That didnt make it any newer " " Dont antique the equipment " |
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#8 |
Registered User
Join Date: Mar 2018
Location: Kuna, Idaho
Posts: 117
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
I'm wondering if it's a fluid volume issue with the master cylinder. The pistons on disc set ups usually have significantly more fluid vume requirements than drums.
Just a thought. Dan
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Forgive my typos, big fingers and little Android digital keyboard....what a mess ![]() 06 GMC Sierra crew cab Z71 DD leveling kit, 34's, bumper, LED lighting. Still doing stuff to it. 67 El Camino Custom 300 Deluxe. In progress. 55 GMC 371 2 1/2 ton. Upcoming project. |
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#9 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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As far as I know there is only one hole in the brake pedal in my 71. I had factory front disc so the hole should be correct.
Adding the rear disc brakes gained me nothing as far as stopping power in normal driving. The only help I have seen on this problem for me was the pedal travel. I need to re adjust my pedal so it's not up against the rubber stopper on the dash bracket. The pedal should have a 1/4" gap form the rubber. The rubber is for rebounding when you let off the brake pedal not where it should rest. I hate getting under the dash so mine isn't set right as of right now. ![]()
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#10 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
This is what I need to do.
CCP Check Pedal Assembly Something that many people are not aware of when upgrading their system is the brake pedal adjustment. Improper pedal adjustment can do the following: •Preload the booster causing brakes to drag and eventually lock up. •Damage the booster's internal components by actuating at an improper angle. •Allow slop in the pedal if adjusted too low. Many vehicles have a second hole on the pedal assembly that was originally intended for power brake applications. The required hole is generally 1" to 1-1/2" lower than the original manual brake hole. If there is no second hole, you may need to drill the hole in the pedal arm to properly align the push rod. The easiest way to determine the perfect location for this hole is to find the center of the push rod's vertical travel to ensure that its actuation is as inline with the booster as possible. 1.Gently lift the end of the pushrod until it stops and noting the location where the clevis on the pushrod locates on the pedal arm. You can mark this location. 2.Then gently push the pushrod down until it stops. Mark this location as well. 3.The proper hole location is in the middle between the two marks on the pedal arm. Mark and drill the new hole in the center of the pedal arm. Attach the pushrod to the pedal arm. ![]() CPP Check freeplay in the pedal by applying pressure to the pedal with your hand and noting how far the pedal travels before resistance is felt. It should be approximately 1/4". This freeplay allows the master cylinder piston to return to the "at-rest" position and prevents preloading the system. Too much freeplay will drop the pedal too far before applying brake pressure and may even hit the floor before applying full braking force to the system. Note freeplay is also dependent upon proper adjustment of the booster pushrod. See "Check the Booster Pushrod" below.) ![]()
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#11 |
Registered User
![]() Join Date: Mar 2005
Location: Jurupa Valley, Ca
Posts: 1,210
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Very interesting conversation. I have a feeling my pedal is also not adjusted correctly. the bump stop is missing and the pedal is no where even close to where it should be per the pictures posted.
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Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC |
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#12 | |
Who Changed This?
![]() Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,430
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Quote:
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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#13 | |
Registered User
Join Date: Nov 2005
Location: Paducah, Ky
Posts: 393
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Quote:
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#14 | ||
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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![]() Quote:
The adjustment will stop it where ever you adjust it to. Quote:
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#15 |
laying low
![]() Join Date: Mar 2001
Location: Searcy, Ark. USA
Posts: 13,265
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Adjusting the pedal just off the rubber stop makes the rubber stop useless doesn’t it? I think of it as a rattle preventative.
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Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross |
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#16 |
Registered User
Join Date: Nov 2005
Location: Paducah, Ky
Posts: 393
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
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#17 |
Registered User
![]() Join Date: Mar 2011
Location: bolivar, mo
Posts: 839
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
I have not had this particular issue on a GM product--But, I had an almost identical issue on a 66 mustang. I changed over to front discs and the problem came along. I researched everything I could think of and finally, just by chance I happened onto an old mechanic (yes, there are people older than me), after explaining my issue, without hesitation he told me it was the pedal adjustment that was the issue. In the end, I adjusted the pedal height (which adjusted the stroke as well) and the problem went away.
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1997 shortie stepside 1968 short stepside 1966 mustang 1966 chevelle ss Dont always go the cheapest route--You can save yourself into the poorhouse! My Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=489030 |
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#18 |
Registered User
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Location: Chattanooga TN
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Dave -- remember a post about the 4wdisc on my 68 ? ^^ This is what ultimately fixed it. Yes, The pedal, Clevis, preloading, etc. all of it. Angle is very important and as Andy mentioned put about 1/4" of 'slop' in the brake pedal so when it hits the top of the pulloff stroke before it hits that rubber pad.
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Chad 1967 C10 SWB - Project Savannah - 6.0/4L80 *Currently underway* 1968 C10 SWB - TOTY 2018, 50th Anniversary Tribute Project * Sold * Pride and Joy 1986 Silverado Short Fleet - Scarlet *Sold* 1985 Silverado Short Fleet *Sold* 2022 Jeep Gladiator Mojave 2001 Jeep Cherokee XJ 4x4 - Lifted, Built 1992 Jeep Cherokee XJ 4x4 - Lifted 2013 Honda Accord EX-L v6 Coupe 6spd (wife's ride) |
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#19 |
Senior Member
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Location: Harrison, Arkansas
Posts: 9,815
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
When I put rear discs on my 55 Chevy 210 I could not get pedal.
I pulled the pedal, and drilled a hole one inch down from the original, lowered the clevis and now I love the brakes. Lowering the clevis gives the piston a longer throw and pushes more fluid to the calipers.
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other Larry Build thread, Arkansas K10 https://67-72chevytrucks.com/vboard/...=755797&page=5 The ability to speak several languages is an asset, but the ability to keep your mouth shut in any language is priceless. |
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#20 | |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#21 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
Thanks guys! I'm going to digest Andy's post and then take a look at my pedal angle. Sure hope this hunch plays out, it's reassuring to hear that others have solved actual problems in the same arena!
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#22 |
Registered User
Join Date: Jul 2014
Location: South East Ohio
Posts: 644
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
I am going to fix this same problem on my brothers car. He has been swapping part for a long time and no results. I looked at it a couple days ago and pedal geometry is certainly part of the problem, if not the whole problem.
I am going to adjust the booster/firewall geometry and check/adjust booster/MC relationship. My thoughts are that if you have an air-tight system and properly matched components, geometry is very likely the culprit. |
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#23 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
On cars (like the Impala) only cars with manual brakes or cruise control got a return spring. Otherwise it's up to the booster. My car is missing its bumper as well, which I found out when I was restoring my next one and went back to look as a reference. So it could be even further out of whack.
I just went out and looked at it, it's not that bad in terms of angle, but it is "highly adjusted", meaning the brake pedal switch is thread in the maximum amount to reach it, for example. And about 1" of rod comes through the clevis. So I'm going to back it off a bunch and see if it changes anything for better or worse. At this point I don't see any "aha!" issues, but am still hopeful.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible Last edited by davepl; 04-25-2018 at 01:10 PM. |
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#24 |
Registered User
Join Date: Apr 2010
Location: So Cal
Posts: 1,437
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Re: Brake Problem 10 Years, Never Solved! - Clevis Adjustment?
It seems, some don't understand what pedal freeplay is or maybe it's just a matter of the explanation.
Freeplay is observed so that no pressure is applied directly to the MC piston, before you place your foot on the pedal. IE, it's the distance between the pedal at rest and the pedal moving the distance needed to up linkage slack. The pedal at rest, should be against a rubber stop. A different hole in the pedal arm would change pedal leverage and pedal travel, but pedal freeplay would be readjust after an such mechanical change is made. Freeplay should be checked with your fingers and not your foot. I think CPP's drawing needed a little help.
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'67 GMC 2500, 292, 4spd, AC |
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#25 | |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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![]() Quote:
Where you put your pedal at rest is a opinion on how high you want your pedal off the floor at rest. It doesn't have to be up against the bumpers. The bumpers in my opinion are for when you let your foot off the brake and the spring slams the pedal back. It's not for the pedal at rest position other than that's where you like it to be. ![]()
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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