Brakes lock up
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Posting Guru
Joined: Jun 2004
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From: Cincinnati Ohio
Brakes lock up
Its a 1976 ford f-100 2wd
When you go down the road and you just barelly tap the brakes both back brakes will completelly lock up on me, I have adjusted them both all the way down and it still does it. The truck was converted over to power brakes. The brakes are new, both pads are the same size, is that right cause what came off they were different sizes. Would it be because of not having much of a front brake because it nose dives. Thanks for the help
When you go down the road and you just barelly tap the brakes both back brakes will completelly lock up on me, I have adjusted them both all the way down and it still does it. The truck was converted over to power brakes. The brakes are new, both pads are the same size, is that right cause what came off they were different sizes. Would it be because of not having much of a front brake because it nose dives. Thanks for the help
Cargo Master
Joined: Jun 2003
Posts: 2,982
Likes: 7
From: Somewhere Saskatchewan
Unbolt the master cylinder and pull it away from the booster.
You don't need to disconnect the lines.
There is a rod with an adjuster.
Back it off and the brakes will apply easier.
Senior User
Joined: Oct 2003
Posts: 480
Likes: 1
From: Elyria, Ohio
Rear brake should apply first. Then front next and will do most of braking. If front first it will nose dive; try applying only front brake to a ten speed bicycle for a more dramatic picture of the effect. Did you use a master cylinder and proportionating valve for power brakes in addition to booster?
Check rear shoes and drums for contamination by diff lube or brake fluid. What condition are surfaces of drums? Rust, scoring, excessive wear.
Check rear shoes and drums for contamination by diff lube or brake fluid. What condition are surfaces of drums? Rust, scoring, excessive wear.
Last edited by rainbowATF; Jan 1, 2006 at 02:16 PM.
Senior User
Joined: Oct 2003
Posts: 480
Likes: 1
From: Elyria, Ohio
Quote from "How Stuff Works":
http://auto.howstuffworks.com/master-brake2.htm
"The metering valve compensates for this, making the drum brakes engage just before the disc brakes. The metering valve does not allow any pressure to the disc brakes until a threshold pressure has been reached. The threshold pressure is low compared to the maximum pressure in the braking system, so the drum brakes just barely engage before the disc brakes kick in.
Having the rear brakes engage before the front brakes provides a lot more stability during braking. Applying the rear brakes first helps keep the car in a straight line, much like the rudder helps a plane fly in straight line."
Discussion follows on proprtionating valve also in article.
I'm sure we disagree on milliseconds, but there are other references and threads here refering to adjustment and operation of rear brakes in relation to front.
http://auto.howstuffworks.com/master-brake2.htm
"The metering valve compensates for this, making the drum brakes engage just before the disc brakes. The metering valve does not allow any pressure to the disc brakes until a threshold pressure has been reached. The threshold pressure is low compared to the maximum pressure in the braking system, so the drum brakes just barely engage before the disc brakes kick in.
Having the rear brakes engage before the front brakes provides a lot more stability during braking. Applying the rear brakes first helps keep the car in a straight line, much like the rudder helps a plane fly in straight line."
Discussion follows on proprtionating valve also in article.
I'm sure we disagree on milliseconds, but there are other references and threads here refering to adjustment and operation of rear brakes in relation to front.
Last edited by rainbowATF; Jan 2, 2006 at 08:30 PM.
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Cargo Master
Joined: Jun 2003
Posts: 2,982
Likes: 7
From: Somewhere Saskatchewan
Yes but.
Lets look at the inside of a rear brake drum.
When the brake shoes are retracted there is a gap between the shoe and drum.
Whereas a brake pad is in constant contact with the rotor.
Yes we are talking milliseconds.
But the system being full of fluid it stands to reason the front will apply before the rear. Due to the fact it takes just that little bit more time to extend the shoes.
Master cylinders are constructed in such a way the rear portion of the cylinder is applied first, then the front.
The front brakes are applied withy the rear portion of the master cylinder.
Pool time dude. You rack em.
When the brake shoes are retracted there is a gap between the shoe and drum.
Whereas a brake pad is in constant contact with the rotor.
Yes we are talking milliseconds.
But the system being full of fluid it stands to reason the front will apply before the rear. Due to the fact it takes just that little bit more time to extend the shoes.
Master cylinders are constructed in such a way the rear portion of the cylinder is applied first, then the front.
The front brakes are applied withy the rear portion of the master cylinder.
Pool time dude. You rack em.
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Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
Originally Posted by stuart1
Lets look at the inside of a rear brake drum.
When the brake shoes are retracted there is a gap between the shoe and drum.
Whereas a brake pad is in constant contact with the rotor.
When the brake shoes are retracted there is a gap between the shoe and drum.
Whereas a brake pad is in constant contact with the rotor.
Cargo Master
Joined: Jun 2003
Posts: 2,982
Likes: 7
From: Somewhere Saskatchewan
Originally Posted by andym
On a properly adjusted drum brake, the shoe is in constant contact with the drum. Just like on disc brakes.
Adjust rear brakes until the shoes are in contact with the drum.
Back off adjsuter so the drum turns freely without drag.
To me that does not say the shoe is in constant contact.
Senior User
Joined: Aug 2005
Posts: 108
Likes: 0
From: Canada,Ont.
Originally Posted by rmalottwtes30
Its a 1976 ford f-100 2wd
When you go down the road and you just barelly tap the brakes both back brakes will completelly lock up on me, I have adjusted them both all the way down and it still does it. The truck was converted over to power brakes. The brakes are new, both pads are the same size, is that right cause what came off they were different sizes. Would it be because of not having much of a front brake because it nose dives. Thanks for the help
When you go down the road and you just barelly tap the brakes both back brakes will completelly lock up on me, I have adjusted them both all the way down and it still does it. The truck was converted over to power brakes. The brakes are new, both pads are the same size, is that right cause what came off they were different sizes. Would it be because of not having much of a front brake because it nose dives. Thanks for the help