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post #1 of (permalink) Old 10-16-2000, 06:40 PM
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Why do my drums lock up??

I know my brakes are very low, and I have new lifetime warranty shoes to put on, I just haven't had the time yet. But why do they lock up when it rains or under light pressure?

1987 YJ Laredo/3" Body/30X9.5" All Terrains/Rebuilt 258/BA 10/5
Rylan D.
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post #2 of (permalink) Old 10-16-2000, 07:26 PM
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Re: Why do my drums lock up??

Usually caused by leaky wheel cylinders. As the fluid leaks out and gets all over the shoes it acts like glue and sticks them to the drum. I have seen it get so bad that you have to back up to get them to release.

post #3 of (permalink) Old 10-16-2000, 07:28 PM
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Re: Why do my drums lock up??

nope, cylinders are fine, any other ideas?

1987 YJ Laredo/3" Body/30X9.5" All Terrains/Rebuilt 258/BA 10/5
Rylan D.
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post #4 of (permalink) Old 10-16-2000, 11:54 PM
 
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Re: Why do my drums lock up??

Your tires might be over inflated.[img]/wwwthreads_images/icons/smile.gif[/img]

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post #5 of (permalink) Old 10-17-2000, 12:00 AM
 
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Re: Why do my drums lock up??

There is a valve in your brake lines, (usually in the bottom of the master cylinder) that holds pressure against the wheel cylinders to make them keep adjustment.
These valves do go bad at times and hold too much back pressure against the wheel cylinders.
You should only have about 5 psi, and no more than 10 psi in the lines.
It's easy to tell with a gauge, unfortunately, most people don't have a gauge for break line pressure.
If you have done several brake jobs, you can crack the bleeder valve and check for pressure there.

Crud can accumulate in the wheel cylinders, and cause the pistons to drag or stick out.
This is easy to tell, just pop the wheel cylinder apart, and look for crud.
If you shoes are REALLY warn out, the pistons can go out too far, and stick too. (Usually in the crud..)

Some brakes are designed so that they will 'Cam Over' when the pads get so worn that the wheel cylinders are about to come apart.
That will cause the brakes to drag.

Another major cause is neglect. When the shoes are changed, or checked, people don't clean the crud out of the brake mechanical workings, and the acidic brake dust, and the corrosive brake fluid, combined with huge temperature extremes, and maybe good doses of mud, sand, dirt and water, all combine to 'plug up' the workings and cause things to stick.

I've seen emergency brake cables, and actuators get rusted and corroded up so badly that when you apply the brakes, the emergency brake doesn't disengage completely.

On very rare occasions, I've seen proportioning valves and safety valves go bad, but that is so very rare I even hesitate to mention it.

How about smashed brake lines holding pressure against the wheel cylinders...

Lot's of things it could be, maybe you have a better idea of what some of them are now....

Good luck, and keep us posted.

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post #6 of (permalink) Old 10-17-2000, 10:29 AM
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Re: Why do my drums lock up??

TR is dead on. I would like to add one other thing though that is commonly overlooked. Check the
backing plate where the shoes ride on it(the raised part of the backing plate that the side of the shoes
rest against.) for grooves with sharp edges. I've seen these worn right through and/or worn so bad that
the shoe will catch on the sharp edges and not release. If that is the case you can weld them back up
and grind them smooth carefully. Just make sure you use a shoe to make sure the pads are all ground
evenly so the shoe rests square against the backing plate. If not then you will open up a whole new set
of problems. Good luck. Nickmil.

post #7 of (permalink) Old 10-17-2000, 10:59 AM
 
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Re: Why do my drums lock up??

Just like every thing else, Brakes didn't escape my scrutiny down through the years...
If you race, you go fast, and if you go fast, you have to stop fast sometimes....
So it stands to reason you will have to upgrade your brakes along with every thing else....



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