2008 Chevy Malibu "incurable" brake vibration

billr

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#16
OK, that is what I use for pads. Still, trying something else may be useful. In the pictures it looks like the left one is scored pretty bad. Is that true? What do the back sides look like? If you have calipers that read down to .001", measure the thickness in several places.
 
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#17
The back is about the same as the front. If I run my finger nail across the rotor I don't catch on any score lines, but if I run my finger tip I can feel the surface is uneven. I can actually feel small divets from the center to outer edge. The rear brakes do not have this, and are perfectly smooth. As are the rotors on my other vehicle.

I think I'll order new pads, get these rotors turned, and start over. I'll measure the hub faces when I get those off. If the hub is not out of spec, and the rotors are still at 1.5 and 2.0 thou, do you think I should just give them a go with new pads and see? Or get some of those shims to get the runout closer to zero?
 

billr

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#18
My opinion? That small bit of run-out of the rotor isn't the problem. I certainly wouldn't shim between the hub and rotor. If you do replace/re-surface the rotors, do some careful measurements of run-out and thickness; then compare to what you have when it starts acting up.

Another "Hail Mary" play: replace both brake hoses, in case they are acting as check-valves and trapping fluid pressure and making the brakes drag all the time
 
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#19
Good point. Caliper sticking was one of the thoughts I had after the 2nd set of brakes went bad. That's when I got out the IR gun and started checking temps.

There is anything else I can check to verify calipers aren't sticking? I'm not seeing any chalking of the pads. When I took the calipers off immediately after driving I didn't find the rotors dragging (the calipers slid right off without having to pry them).
 
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#20
As always when the gang here searches the collective brain cells and no consensuses I look at TSB;s - getting real detailed (anal) did you check the rotor lateral runout - seeing the spec had me say wtf thats a tight tolerance .002.
 

billr

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#21
Did I read correctly, at one point you replaced the rotors but left the old pads in and that cured it for a while? That seems to accuse only the rotors.

As tedious as it sounds, I would try getting repeatable results; putting on new/good rotors to confirm it is fixed, then putting back on the "bad" rotors and confirming the problem instantly returned. Do this several times. Worse yet, I would do this on one side at a time...
 
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#22
As always when the gang here searches the collective brain cells and no consensuses I look at TSB;s - getting real detailed (anal) did you check the rotor lateral runout - seeing the spec had me say wtf thats a tight tolerance .002.
The spec is 0.002" on Total runout? I was going by a spec of 0.003", measured max 0.002"

Did I read correctly, at one point you replaced the rotors but left the old pads in and that cured it for a while? That seems to accuse only the rotors.
Vibration started with OE pads/rotors. Replaced pads and rotors, 4-5 months the vibration came back. The 2nd time I replaced the rotors only. I used the "best" rotors the store sold. The vibration went away for 4-5 months. This is where I'm at now.