Brake master question (1 Viewer)

[Seamus]

Did the PO install the wrong master when “fixing a leak”. I replaced a leaking drum cylinder in the rear so I am not losing fluid anymore. The shoes are new but I keep locking up my rear wheels going super slow and it is driving me nuts. My tires are older than I wish they were but I don’t think they are the problem. I can lock up the rear wheels at about two miles per hour and these tires howl really bad. I have tried backing the adjusters off the back but it hasn’t helped. It is a 1969 and has drums on all 4 corners.

 

[upperblack]

Don’t believe that’s the correct master.
Here is mine on my 69

 

[Seamus]

Don’t believe that’s the correct master.
Here is mine on my 69
View attachment 2499678

But it is a single outlet, correct? I am trying to figure out if there is a proportioning valve or something I am missing. I think the tires may have gotten s***ty over it looks like 5 years. I recently picked the truck up.

 

[upperblack]

Single outlet, single circuit, no proportioning valve

 

[Seamus]

Single outlet, single circuit, no proportioning valve

Maybe the tires are trash, it doesn’t make any sense. I’ve driven on much older tires in other vehicles and not had this kind of problem

 

[3_puppies]

does the brake line go to the front axle?
do the front drums bleed properly?
have you adjusted the fronts tighter?

single circuit means all 4 wheels should be getting the same amount of preasure.
tires will have no affect on the locking up.
my WAG is the fronts are not in the circuit and all preasure is going to the rear.

 

[Seamus]

does the brake line go to the front axle?
do the front drums bleed properly?
have you adjusted the fronts tighter?

single circuit means all 4 wheels should be getting the same amount of preasure.
tires will have no affect on the locking up.
my WAG is the fronts are not in the circuit and all preasure is going to the rear.

I have not bled the front, but the pedal feels fine. I will put the front on stands and check that way. I have everything adjusted by the book and have backed the rears off and it helped to a point. The reason I mentioned the tires is that they are 5 years old. On my other cars that is usually the limit I have, this was driven less than 500 miles on them before I bought them and was allegedly kept in a garage the whole time. They slide going VERY slow on good pavement is why I think they are bad. But it doesn’t necessarily explain why it is only the rears.

 

[Mtntopper]

Did the PO install the wrong master when “fixing a leak”. I replaced a leaking drum cylinder in the rear so I am not losing fluid anymore. The shoes are new but I keep locking up my rear wheels going super slow and it is driving me nuts. My tires are older than I wish they were but I don’t think they are the problem. I can lock up the rear wheels at about two miles per hour and these tires howl really bad. I have tried backing the adjusters off the back but it hasn’t helped. It is a 1969 and has drums on all 4 corners. View attachment 2499655

View attachment 2499656View attachment 2499657

View attachment 2499660

View attachment 2499662

It sounds to me like there is air in the rear lines. I've found the rear brakes to be a real PITA to bleed properly.

 

[AntFarm]

Tread carefully on this. Brakes which are too strong on the rear in a short wheelbase can be a disaster really quick. I agree that it sounds like you have almost no brakes in the front, and you might have air in the lines. Put both axles up on jackstands. Bleed all four corners using a friend at the pedal to get a good gush out the bleeder screw. Re-adjust all eight cylinders, starting with full wheel lockup, then back off 2-3 clicks. If you have already "backed off" the adjustment on the rears, then they are probably too loose. I say this because the difference between a locked up wheel and a properly adjusted wheel is only about 2-3 clicks at the most. If the bleeding and adjusting procedure reveals a problem, then further exploratory surgery is required. Might need to pull all 4 drums and take a look at the condition of all cylinders, adjustment wheels, and overall brake condition. A common problem with adjusting land cruiser drum brakes pre 8/80 is that folks will properly adjust one of the shoes in a wheel, but not the opposing shoe. Each shoe gets adjusted independently within a wheel. Lockup the wheel with one shoe, then back it off. Then, lockup the wheel with the other shoe, then back it off the same number of clicks as the first shoe. Repeat at each corner. It's a lot of work, but super satisfying to have it right.

 

[Seamus]

Tread carefully on this. Brakes which are too strong on the rear in a short wheelbase can be a disaster really quick. I agree that it sounds like you have almost no brakes in the front, and you might have air in the lines. Put both axles up on jackstands. Bleed all four corners using a friend at the pedal to get a good gush out the bleeder screw. Re-adjust all eight cylinders, starting with full wheel lockup, then back off 2-3 clicks. If you have already "backed off" the adjustment on the rears, then they are probably too loose. I say this because the difference between a locked up wheel and a properly adjusted wheel is only about 2-3 clicks at the most. If the bleeding and adjusting procedure reveals a problem, then further exploratory surgery is required. Might need to pull all 4 drums and take a look at the condition of all cylinders, adjustment wheels, and overall brake condition. A common problem with adjusting land cruiser drum brakes pre 8/80 is that folks will properly adjust one of the shoes in a wheel, but not the opposing shoe. Each shoe gets adjusted independently within a wheel. Lockup the wheel with one shoe, then back it off. Then, lockup the wheel with the other shoe, then back it off the same number of clicks as the first shoe. Repeat at each corner. It's a lot of work, but super satisfying to have it right.

I am 3 clicks off locked up in the front and an additional 1 or 2 in the rear at the moment.

 

[AntFarm]

Just re-read your earlier posts. If the truck is a recent purchase, I would definitely baseline your brakes. If you haven't inspected all of them, then now's the time. You only replaced one cylinder in the rear? I would recommend replacing all cylinders, not just one, unless they are all in stellar condition. But you would only know by taking off the drums and inspecting everything. Before that, I would still do a complete bleed of all four corners and see if any problems present themselves. Also, it sounds like you already don't like your tires anyway, so you could buy a new set of whatever you prefer and eliminate that variable from the equation.

 

[Seamus]

Just re-read your earlier posts. If the truck is a recent purchase, I would definitely baseline your brakes. If you haven't inspected all of them, then now's the time. You only replaced one cylinder in the rear? I would recommend replacing all cylinders, not just one, unless they are all in stellar condition. But you would only know by taking off the drums and inspecting everything. Before that, I would still do a complete bleed of all four corners and see if any problems present themselves. Also, it sounds like you already don't like your tires anyway, so you could buy a new set of whatever you prefer and eliminate that variable from the equation.

Master is new, all shoes are new, I had one leaking cylinder I replaced the pair. These are the best looking drums I have ever had apart.
The thing I don’t like about the tires is based mostly on the skidding that is happening. They are 5 years old. I have been out of trucks for about 20 years but in my performance cars 5 years is about the limit for tires. These have no miles on them I was initially thinking that the rubber got hard and was a contributing factor.

 

[3_puppies]

5 years is nothing for a tire as long as it is not dry rotted from sitting in the sun

the tire is not causing the the wheel to lock up and skid that is a braking issue, to double check put different ones on there and see what happens

 

[Mark Jennings]

How are the shocks and springs....does it have extended shackles in the back....there are no broken shock mounts, etc....if the front dives at all under braking, it’ll bias a tremendous amount of weight forward unloading and locking up the rear....irregardless of tire type.

Sounds like you’ve convinced yourself the brakes are bled and adjusted correctly....check out the rest of the chassis components. Even something as simple as tire pressure can affect braking performance.

Good luck with you’re quest....mine ended with 4 wheel disks.

 

[Seamus]

How are the shocks and springs....does it have extended shackles in the back....there are no broken shock mounts, etc....if the front dives at all under braking, it’ll bias a tremendous amount of weight forward unloading and locking up the rear....irregardless of tire type.

Sounds like you’ve convinced yourself the brakes are bled and adjusted correctly....check out the rest of the chassis components. Even something as simple as tire pressure can affect braking performance.

Good luck with you’re quest....mine ended with 4 wheel disks.

Springs and shocks have less than 1500 miles on them, same as the tires. PO replaced all before selling. I have receipts.

 

[Mtntopper]

Did the PO install the wrong master when “fixing a leak”. I replaced a leaking drum cylinder in the rear so I am not losing fluid anymore. The shoes are new but I keep locking up my rear wheels going super slow and it is driving me nuts. My tires are older than I wish they were but I don’t think they are the problem. I can lock up the rear wheels at about two miles per hour and these tires howl really bad. I have tried backing the adjusters off the back but it hasn’t helped. It is a 1969 and has drums on all 4 corners. View attachment 2499655

View attachment 2499656View attachment 2499657

View attachment 2499660

View attachment 2499662

These brake systems work well and it sounds like you have the right parts in place. I still believe that you need to get the rest of the air out of the system.

 

[Seamus]

These brake systems work well and it sounds like you have the right parts in place. I still believe that you need to get the rest of the air out of the system.

I’ll try again tomorrow. I have bled many brake systems over the years and used a vacuum bleeder this time, i have no bubbles coming out of the line. I will try it tomorrow with my wife on the brake pedal.

 

[Mark Jennings]

Springs and shocks have less than 1500 miles on them, same as the tires. PO replaced all before selling. I have receipts.

So the new tires are 5 years old with only 1500 miles? And the chassis components are good....then check your air pressure....then drive the rig with your foot on the brake...get them good and hot....break in the shoes....

20 slow downs light peddle pressure from 50 to 20, let the brakes cool down between runs (few minutes) no panic stops....then see how they react.

Probably grabbing because the

 

[Mark Jennings]

So the new tires are 5 years old with only 1500 miles? And the chassis components are good....then check your air pressure....then drive the rig with your foot on the brake...get them good and hot....break in the shoes....

20 slow downs light peddle pressure from 50 to 20, let the brakes cool down between runs (few minutes) no panic stops....then see how they react.

Probably grabbing because the

Brakes are new, high friction coefficient...need to drag some of that down.

 

[Seamus]

Brakes are new, high friction coefficient...need to drag some of that down.

Brakes are not brand new, brakes have about 1000 miles I put on them, they had been recently changed before I got the truck. I replaced 2 cylinders on one drum.