Squeaky Drum Brakes & A Terrible Mechanic.

[MIKE S]

No matter how perfect you turn the drum it will almost always feel like uneven rubbing when you rotate the drum. Experience with repairing brakes over time will let you get the feel on how much drag is to much.

[Spool]

Thanks Mike.

Well, this afternoon I decided my brakes were a little softer than I preferred.
So, I adjusted each side roughly 4 clicks and the pedal felt great, but the squeak came back after I went to the car wash.

Mmm.....

Maybe tomorrow, I'll adjust them backward 4 clicks.

[MIKE S]

Unless those 4 clicks is making it drag heavily, it is not the cause of your squeak.

[Spool]

Well, if it only squeaks, when I apply the brakes it has to be the shoes on the drums no?

Unless, the pressure from the shoes is causing the Axel to move because there’s no spacer?
(I’m blindly reaching on that one.)

[JohnnyPopper]

Spacer has no effect. You’ll need to inspect the shoes and drums.


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[Spool]

Well the shoes are brand new and I’m 90% sure I installed them correctly. I posted all the pictures above.

I’ve measured the drums (pep boys did and that was debatable.)

Thus, I’d we can confirm it’s not the shoes, then it’s the drums? But what about the drums needs to be inspected- that they aren’t perfectly round?

The strangest part to me is that it’s intermittent. If I back out of the driveway at 5mph they’ll barely squeak when I come to a complete stop. Then maybe they’ll squeak later, maybe not. I can’t seem to draw a connection to it other than I cannot brake heavily unless I’m willing to listen to it squeak.


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[JohnnyPopper]

I’m starting to think they may be out of round, causing the shoe to oscillate, or moving them left - right, transferring friction to the back plate


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[JohnnyPopper]

Measuring the inside diameter is different from measuring out of round.


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[Spool]

Measuring the inside diameter is different from measuring out of round.

I see. Well, I’m start pricing out new drums.

How would the drum go out of round? I watched a video on YouTube, I think Eric the car guy, where he showed the workings of the machine that widens the drum- it seemed like the only mistake you could make would be taking too much off.

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[JohnnyPopper]

Okay, but you will not know if they are out of round till you have a competent shop do the work.

[bd]

The squeak is caused by the drums singing.  It is a consequence of friction between the lining and drum surfaces.  The linings grab-release-grab-release-grab-release-grab-release at high frequency.  The result is that the drums resonate and squeal.  Out-of-roundness will not cause squeal.  Out-of-round drums can cause annoying brake pulsations or produce a pulsing squeal.  But the squeal itself is due to resonance, not out-of-roundness.  Essentially, any circumstances that alter the coefficients of friction between the lining and the drums can produce a squeal.  Hence, relatively hard fleet or commercial grade lining is more prone to squeal.  Cold moist lining is more prone to squeal (as well as grabbing).  Hot lining is more prone to squeal.  Glazed lining is more prone to squeal.  Drums that are polished or that have hard spots are more prone to squeal. 

Look.  Brake shoe lining is a molded, porous, composite material composed of high friction particles in a binding matrix.  Generally, brake shoes need to undergo a period of heat cycling from moderate use in order to fully cure and achieve a stable temper.  Based on your narrative I suspect that the surfaces of the shoes glazed ever so slightly as a result of the repeated aggressive brake applications, initially.  Hammering the brakes right out of the gate was a bad idea.  Remember, I said to get a proper manual adjustment and not rely on the self-adjusters?  Compounding the problem, the lining hasn't fully conformed to the drums yet.  High spots on the lining are doing all the braking, which requires a little more pedal pressure.  This is one reason, besides ensuring concentricity, that brake drums are machined when replacing shoes.  The roughened drum surfaces accelerate the seating and conditioning of the shoes with normal braking.

[VileZambonie]

Vile, I kept the drums for now, but as mentioned before, I feel like I can hear the unevenness in it when I turn it.

Drums not only out of round but tapered or bell mouthed will cause the shoes to lift and vibrate, hence your squeal. Looks like you did two things that need addressing. Replace the missing thrust washer and replace or machine the drums.

[bd]

That's reasonable.  But how do you prevent a recurrence?  Replacing the drums will increase drum mass which will alter the harmonics.  Even if drums are perfectly round and concentric when first installed, what prevents them from distorting with repeated heat cycles?  This isn't to argue with your statement but how do you ensure long-term reliability?

[JohnnyPopper]

If you have your old shoes, you can check to see if the wear pattern reveals if they are tapered, or bell mouthed.

Spool, if you're not familiar with those terms, the shoes should wear flat, or square with the inner surface of the drum. In some cases, that wear pattern can be distorted by various factors and result in a irregular wearing inside the drum. New "square" shoe will be affected adversely until they adapt to the irregular surface inside the drum.

In all fairness to the drums, if they are within tolerance, the culprit may lie in their being tapered, bell mouthed per VZ, or glazed smooth. I recall some pics that showed that.

Were this my truck, I would have them checked for being round, square, and then have them machined to cut the glaze and reinstalled.

 Paired with new, albeit HD shoes, and mild braking until they are acclimated per the bd'ster, you should get them to behave.

[MIKE S]

Here is another thing to consider. This is my point of view. Replacement drums and rotors are made offshore and the quality of the materials, casting and machining are inferior to what would have been installed from the factory back in the day. I have seen replacement rotors were the the center of the stud bolt pattern were not indexed with the centerline of the bore. That made the wheel move up and down while rotating. My point is that you could have a set of drums that has issues that may not have been present with the original drums. I don't think if you bought a set of high dollar name brand drums that you wouldn't be receiving inferior products. Short of finding a good set of used oem  drums I'm not sure if that would solve your squeak. I think I would take the drums back off and sand the circumference of the braking surface with 80 grit utility cloth and lightly sand the shoes. Make sure you were a mask. Spray with brakeclean and reassemble. This time let the brakes break in before making any hard panic type stops.