2008 Chevy Malibu "incurable" brake vibration

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#1
Make
Chevrolet
Model
Malibu LS Classic
Year
2008
Miles
119,000
Engine
3.5
Hi,

Used to be a member of BAT over 10 years ago, sadly lost track of the forums as life got busy. I have a brake problem that has me stumped. I feel like I've tried everything in the book but this problem just keeps returning. Here's a short history:

1. October 2017 at 107k miles the car developed a really bad vibration when braking, the whole front end would shake violently. At that mileage I figured it was just time for new brakes so I replaced the OEM rotors and pads with Raybestos. Brakes were nice and smooth for a few months.

2. October 2018 the brake vibration had gotten just as bad again. I checked everything up front: found I had a loose outer tie rod, replaced that and had an alignment, same vibration. Found that one of my caliper pins was sticking so thought "ah ha" that must be it. Cleaned pins well, replaced all the brake hardware, rubber pieces on pin tips, lubed with Sylgard. Installed new premium coated rotors from NAPA, kept same pads. Also flushed the brake fluid. Nice smooth brakes until 5 months later. Around town they're okay, but over 55mph and the brakes shake the whole car. At slow speeds I can feel a "grab/release" type of feeling in the front while braking.

3. Checked and re-checked the whole front suspension. Measured the total indicated runout. LF 0.0015", RF 0.002". These are repeatable measurements, made 1/2" in from the outside edge. The caliper pins all move freely and smoothly. Pads slide easily in the brackets.

I'm stumped. Does anyone see something I've overlooked? Do I just get the rotors skimmed and try another brand of pads? I've even gone as far as to check the rotors and calipers with an IR gun to see if any are overheating after a drive, they're all even temperatures and nothing crazy. I'm not aggressive with the brakes. Rear rotors and pads are also new and function fine, parking brake holds, etc.

Thanks for any suggestions,
-Michael
 

billr

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#2
I gotta ask... does this have ABS?
 
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#3
Yes, has ABS. Doesn't feel like abs action when the vibration occurs... Not as much in the pedal as the whole front end shaking to pieces.
 
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#4
Braking at 55mph...if you hold the steering wheel lightly does it act like a washing machine center agitator (top loader)?

Are you using proper torque and tightening pattern?

Have you measured runout on the hub flanges?
 

billr

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#5
Have you aligned the wheels lately; got the numbers it "went out the door" with? Have you tried swapping tires front-to-rear?
 
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#6
Yes, it shakes the wheel L-R even at 35 mph if I let go while braking.

I have only measured the total runout at the rotor. Left front 1.5 thou, right front 2.0 thou. I was using 3.0 thou as the limit. I did not measure the hub flange by itself. I also didn't think to check end play in the bearing assembly... is there a spec on that? Less than 0.5 thou?

95-100 ft lbs on the lug nuts with a torque wrench. I sure hope I know how to torque 5 lugs correctly! ;)

The front end was aligned after I replaced the damaged tie rod end. The vibration predates that whole thing by a year. I probably have the "after" specs and will try to find them when I get home.

Tires have be rotated with no change in the brake vibration.

The two times I've installed new pads/rotors on the front, the brakes were smooth as a brand new car for 4-5 months. It gradually got worse until it was as bad before. That is what has me stumped. Unless 2.0 thou runout is marginal on the runout? Do I need to get it less than 1.0 thou to have long lasting results?

Edit--FYI, this is what the rotors looked like when I measured the runout:

Left Front:


Right front:
 
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#7
My theory is that a problem with the hub/hub flange causes a problem of uneven wear to the rotor. A new rotor masks the problem for a while but after many miles, there is a cumulative effect that becomes noticeable.
Theory #2. Your wife sends Junior on a beer run while you are sleeping...he cooks the brakes.
 

billr

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#8
Are you reading run-out on both faces of the rotor, both surfaces simultaneously?
 
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#9
I'm leaning toward theory #1 as well, since the original brakes were smooth for 100k miles and then suddenly became very vibrational. When I replaced them I didn't see anything visibly wrong--pads still had life, etc. But after checking the rest of the suspension found nothing else to blame.

Bill, I'm using a dial indicator to measure only the face of the rotor for total runout. I have not measured thickness variation of the rotor with a micrometer. That is something else worth checking. Is there a spec for max thickness variation on chevy rotors?

What is the runout spec on the bearing hub flange?
 

billr

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#10
Wow, I just checked in my '69 FSM: run-out was .002" TIR and "thickness variation" .00005"

I would not think either would be that critical, but that was back when discs were rather "new", so maybe they were being very cautious. I drove a truck for many years with rotors surfaced by hand on a sander, it was fine. The guy that did it was an exceptional craftsman, of course. (not me)
 
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#11
A "warped disc" is perceived as being similar to a record that will not lay flat on a turntable. That is a Grade B problem because the caliper can wiggle on its guides to reduce vibration. "Thickness" or parallel variation is a more serious and common problem. Imagine the difference that your hands would have to deal with if you were sliding down a smooth steel pipe or a chain of the same size.
 
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#12
What about hub bearings and CVJ's, was a problem with another GM vehicle made a lot worse when braking. Your half axle threads sure look rusty, how is the rest of the bearing? Do you check your pads for returning to the home position after releasing the brake pedal?
 
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#13
Bill, see the alignment specs below. It was not the best alignment tech I ever had--as soon as I drove out I had to turn around and come back bc it was pulling right. But the vibration started a year before and was not even slightly affected by replacing the tie rod and aligning.

malibu alignment.jpg

Also found the brake specs for my Jag XJ, that is about the same as others. 0.004 on total runout, 0.0006 on the hub face. No spec on thickness variation. I will have to check the hub.

jag brake specs.png

I'm not going to jump to esoteric causes like CV joints. There's nothing to indicate any issues with the axles. When I replace the brake rotors the car is as smooth as new. Then after 4-5 months the vibration comes back. As far as rust, must be an optical illusion in the photo. Car has never seen salt in its life. I could probably break that hub nut and then spin it off with my fingers.
 

billr

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#14
Hmm... caster is one of the most important, and they didn't even check that before or after???

What type of pads are you using? I like ceramic (well, asbestos is my real preference, but...). Throwing a set of different type/brand pads at it is pretty cheap and easy to do, probably worthwhile to try.
 
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#15
I do not believe caster is adjustable, nor camber on this vehicle.

I used Raybestos ceramic (OE type). I believe NAPA and Delco are rebranding of these same pads. I could try is PowerStop which appears to be a totally separate company.