Rt.Rear Brake Sticking

[tbird430]

My good neighbor across the street is having a new problem on his newly acquired '64 hardtop.

After he drives his car for short time, the right rear brakes start locking up. He has disconnected the parking brake system to eliminate that as possibly being a reason for the sticking. He's replaced the shoes, wheel cylinder, and bled what seems like a gallon of brake fluid through the rear brake system.

The shoes & rear wheel get so hot he's even had the right rear (old??) tire blow out!! He stated you couldn't even touch that wheel it gets so hot from the brakes sticking.

He had to replace the rear brakes shoes again since this started because on another weekend in which he & another neighbor torn into this problem the brake linings simply cracked & fell apart in pieces when they removed the drum. They had gotten that hot again and broken down!!

The axle tube bearing turns, sounds, and feels fine too. So that's not a problem.

He says the rest of the brakes seem fine. The front drum brakes don't pull you in a left/right direction. The brake pedal releases fine & the brake lights go out like they should.

The left rear wheel never locks up, so we didn't think it would be the rear flex hose either. I asked him to inspect the right rear steel brake tube from the flex hose junction block to the wheel cylinder. He said it looks fine & not pinched or dented in anywhere. And again, the right rear brake bleeds fluid fine??

My neighbor hasn't figured out how to post on here yet & asked me to start this thread, just to get some more ideals on what he could try to fix this T-Bird....

[Joe Johnston]

2 things to quickly check

1-usually one lining is larger than the other. Make sure they are installed correctly (largest to the front or rear as determined by the shop manual or by searching here). I always have to check which goes to the front or rear when mounting them.

2-check the backing plate where the shoes rub or slide against. There may be a ridge worn into the backing plate which catches the shoe and keeps it from releasing. A bit of weld and some grinding to smooth things over before a bit of grease and the shoes can move freely.

Has to be something that can be identified - especially if the rubber hose is OK.

[jopizz]

Has he checked the drum for out of round. I would imagine with all the heat it's been generating that it's probably warped. Has he spun the tire after putting the brake on to see if it's releasing. Has he checked to make sure the rubber brake hose isn't too close to the exhaust causing the fluid to expand. Just a couple things to check.

John

[simplyconnected]

Both Joe and John covered it pretty much.
Brake shoes come in sets of 'primary' and 'secondary' linings. Sometimes they are marked on the side of the lining. You can sometimes tell which is which by holding them next to each other. The long, secondary shoe always faces the back of the car. Sometimes the lengths are the same but the lining materials have different friction coefficients (and different color). Still, there is always a primary and a secondary lining.



Having said that, I have seen it all: Installations where both long secondary shoes were on the SAME side, leaving both short sets on the other side. <--this usually makes the installer wonder why one side pulls.

If your brake has suffered excessive heat, the springs can lose their 'memory'. This will certainly cause a shoe to drag and create more heat. Pull vigorously on the retract springs. Make sure they are tight. And always check the back plate for worn pads as Joe described.

[tbird430]

Thanks fellow Birder's.

Are you getting all of these ideals Chris? (neighbor)

See the small, gray/blue "post reply" icon down at the bottom of the page? Lower left corner? Should see a few papers & a pencil by it. I need to show you how to post & reply on here... Soon.

-Jon in TX.

[cdhowell]

There are left and right adjusters as well. The wrong one will cause the brake to tighten every time you step on the pedal.

[tbird430]

WOW!! I overlooked that possibilty.

This might be it....

[simplyconnected]

There are left and right adjusters as well. The wrong one will cause the brake to tighten every time you step on the pedal.

I respectfully disagree. A proper setup will tighten the brakes. The wrong star wheel will loosen the brakes.

Let's understand the brake system a little deeper. We know that the shoes expand against the drums, causing friction. So, what stops the shoes? They don't spin in circles, but they 'float'. Those little nails are designed to move around. The wheel cylinder pins are a ball-and-socket fit, so they can move as well.

What stops the shoes? That huge bolt at the top with 9/16" thread that goes through the back plate. They simply call it a 'anchor pin'. Shoes have that half-moon shape at the top that hits the anchor pin. When you hit the brakes in reverse, the whole shoe assembly rotates until the opposite half-moon hits the anchor pin.

If a shoe is on the anchor pin (the brake pedal is pressed), what forces the shoes out farther? The wheel cylinder pistons are free-floating and so are the shoes. If one shoe is tight against the pin, fluid pressure is shared between the pistons causing the opposite shoe to dig in more, which puts even more pressure on the anchor pin. That causes the wheel to stop the car.

Squarebird front brakes have an anchor pin that screws directly into the spindle. That is the same, huge 9/16" bolt hole that these disk brake companies use in their caliper bracket setups.

So now we have a 'rocking' motion with the floating brake shoes. The more 'out of adjustment' they are the more they have room to rock. That's where self-adjusters come in. When the brakes are applied with the car in reverse, that a cable pulls the adjustment arm up to the next star wheel notch. If the brakes are 'in adjustment' shoe assembly movement is limited and the adjustment arm will not reach the next notch. - Dave

[Short Steppin']

I am the new owner of this '64 Thunderbird (I believe its the same one from Witchita Falls). So I will be following up on the questions about it and issues it has. I've noticed that the brake pedal doesn't depress entirely, theres quite a bit of slack in the pedal. A hard stop at a stop sign, and release of the pedal the car still acts as if the right rear brake is engaged. However, if i put my foot behind the brake pedal and pull out on it, the brake releases and I'm on my way. To me, this is where the problem is. I don't think the pedal/booster is releasing all the way.

[simplyconnected]

Dylan, welcome to Squarebirds.org. I hope you get your brake situation straightened out. If you have a single-piston master cylinder, all brakes get the exact same fluid pressure.

In cars this old, sometimes rubber hoses de-laminate and obstruct fluid flow. But your car has only one hose that services both rear brakes. Even so, both rear brakes see the same line pressure. If both brakes don't release together, there is something wrong with the sticking wheel's brake.

You might have two problems. One with the brake and one with the booster.

A hard brake pedal usually indicates a bad booster or leaking master cylinder (into the booster). Since the brake pedal is directly connected to your booster, pulling up on the pedal makes sense.

Is your engine smoking (from burning brake fluid)? Are you adding brake fluid frequently?
lift the back wheels off the ground, hit the brake, and physically feel if one or both wheels are sticking. You can do this with the engine off. Let us know what you found. - Dave