1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Rear Drum Brakes Partial Locking

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Old Oct 28, 2010 | 05:07 PM
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Rear Drum Brakes Partial Locking

I searched and I couldn't find anything on this topic.

Situation: Putting the drivers side drum brake bake together after replacing the axle shaft.

After several different positions of the star screw the rotation ends up stiffening on 1/3 of the rotation (say between 8 and 12 on a clock) but when I pass through it it eases up.

What could be causing this?

Thanks.
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Old Oct 28, 2010 | 06:32 PM
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take the adjuster apart and clean the threads of any brake dust that has accumulated. inspect teh threads to ensure that they are clean. sounds like the threads may be a little buggered up or an accumulation of brake dust.
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Old Oct 28, 2010 | 06:42 PM
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Thanks,

I think I need some clarification in my question, the adjuster isn't stiff, the wheel rotation is stiff.
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Old Oct 28, 2010 | 11:57 PM
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Are you installing new shoes also? I'm almost tempted to say the drum may be out of round. But I am going to assume they are the same brake parts as came off. Make sure the adjuster threads are clean and such, check the contact points and springs to make sure the shoes are binding up somewhere and dragging on the the drum. That's all I can think of right now...
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Old Oct 29, 2010 | 02:17 AM
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ensure that the parking brake is not engaged and loosen the cable at the lever and adjust the shoes to the drum. then once both sides are adjusted, set your parking brake adjustment.
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Old Oct 29, 2010 | 09:22 AM
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From: "Haystack" Hayward, CA
Originally Posted by mazdaverx713b
ensure that the parking brake is not engaged and loosen the cable at the lever and adjust the shoes to the drum. then once both sides are adjusted, set your parking brake adjustment.
Blah, didn't think of that last night...
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Old Oct 30, 2010 | 11:57 AM
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I am putting the same drum/shoe/hardware that was in it before. Parking cable has been loosened. The drum will spin, however, when I go and fully tighten the lug bolts for the wheel the whole thing locks up.

It is almost like the axle is a few mm too short and the drum locks against the backing plate once the lugs are on.

Is there a safe way to add separation between the axle shaft plate and the backing plate, or does this not make any sense?
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Old Oct 30, 2010 | 06:09 PM
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No, there's not. Any seperation there has to carry 1/4 of the weight of the car as angular pressure that moves with each rotation of the tire- - and this will also prevent your drum from engaging the shoes properly.

If you're putting on the same parts and the problem didn't exist before, something's not right.

Make sure the rim of the backing plate hasn't gotten tweaked.

Make sure the shoes are properly seated on the backing plate, and are in the right positions.

Check the drum for out-of round with a caliper; even a slight out of round condition will cause a cyclic drag.
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Old Oct 30, 2010 | 06:41 PM
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Have you tried putting the drum and wheel on without the brakes shoes? Try that and see if anything is still rubbing.
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Old Oct 31, 2010 | 05:41 PM
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Thanks Kansas, I took out the shoes and had just the drum on and it worked. Which led me to more carefully examined the parts that I had. Turns out, the wheel cylinder that was on the "new" axle was bad. Replaced it with the one that I had before and everything runs smoothly.
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