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Old 10-10-2018, 12:42 PM   #1
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Disc brake chatter after a brake job?

Last week, I intended to do a quick front brake pad replacement, but as it usually goes, a 60 minute job turned into several day project. As I removed the calipers, I noticed the rotors were cracked, which required removal of the hubs, purchase of a hub nut socket, calipers, and rotors (trip 2 to the auto parts store) and removal of the wheel bearings.

Since I have never pulled a 4wd front end apart before, I ended up taking the Ford hub apart far further than needed, but I'm getting ahead of my self here. After removal of the wheel studs and tone ring, I cleaned everything up, washed out the bearings and repacked them, installed new grease seals (trip 3) replaced the studs in the new rotor, reinstalled the tone ring, replaced the hub assembly on the spindle, adjusted the wheel bearings (hand tight, then backed off ever so slightly) installed the new caliper and carrier, lightly greased the spots where the pads contact the caliper pistons and all sliding surfaces, installed the hub's (several times until I got all the parts correctly installed, (I think) bled out the air (trip 4 for more brake fluid) and went for a test drive to bed in the pads.

I immediately discovered that I now have a brake chatter that starts at the very end of a stop. That's to say, at about the last five revolutions of the wheel there is a chattering vibration in the brakes. So far, I've driven less than one mile, since as soon as I got back I pulled the steering box and installed a RedHead. I also double checked the torque on all the bolts, made sure there was a little disc brake grease on the sliding surfaces including where the pistons contact the pads, and re checked the wheel bearing nuts. About the only thing I can think of is that the pads are not broken in yet, but I've done plenty of brake jobs before and never had this happen. Any ideas what the problem may be?
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Old 10-10-2018, 12:58 PM   #2
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Where did you source the rotors? and were they burnished, I've seen this happen with Chinese rotors more than once, It might go away after some use, if you think you've got them bedded in, try a couple of hard stops.
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Old 10-10-2018, 01:00 PM   #3
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Do your calipers use shims? It can be pretty important to get the shims in correctly, since they make subtle differences in how the pads meet the rotors. If you've done brake jobs before you probably know, but god knows I overlook stuff like that sometimes.

Only other thing I can think of is maybe there's some kind of manufacturing coating on the rotor faces that hasn't worn off -- sometimes they come with a little oil to stop them from rusting in storage.
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Old 10-10-2018, 01:07 PM   #4
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Do your calipers use shims?
Only other thing I can think of is maybe there's some kind of manufacturing coating on the rotor faces that hasn't worn off
Yup, all new stainless shims that fit snugly. The rotors came from the local auto parts store, and look like they were double disc ground, total run-out was around .005. They did have an oily coating that I tried to remove using some brake-clean and a paper towel, but I've never heard of burnishing. What is that?
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Old 10-10-2018, 01:42 PM   #5
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I wasn't very clear, I'm sorry, it's the same as bedding, which is what you did, but, I've seen some offshore rotors which claimed to be prebedded, something I would avoid, I don't think you have a serious problem, but there seems to be a lot of complaints regarding rotors lately, good luck, I'm waiting to find out what the problem is.
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Old 10-10-2018, 03:09 PM   #6
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Sometimes it's uneven transfer of pad material onto the rotor surface. One easy way this happens right away is coming to a hard stop and leaving your foot on the brake pedal...it leaves a pad "imprint" on the rotor with a different coefficient of friction than the rest of the rotor.


Did you bed in the pads?? 4-5 hard stops from 55-60 mph almost to a stop, then get off the pedal...this evenly transfers new pad material onto the rotor face after a brake job without leaving a pad shaped "imprint".
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Old 10-10-2018, 05:08 PM   #7
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Did you bed in the pads?? 4-5 hard stops from 55-60 mph almost to a stop, then get off the pedal...this evenly transfers new pad material onto the rotor face after a brake job without leaving a pad shaped "imprint".
I did pretty much exactly that, but wasn't able to gain that much speed in my neighborhood. Still, I did get them plenty hot, and then without applying the brakes to a full stop I parked it to allow them to cool. That's how I have always done it. I'll head out for another test ride later today after I finish bleeding the new steering box.
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Old 10-10-2018, 05:20 PM   #8
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Last week, I intended to do a quick front brake pad replacement, but as it usually goes, a 60 minute job turned into several day project.

And I thought I was the only one... :-)

.005" runout is about right. I always clean my rotors with brakekleen, and am careful to not get any anti-seize or grease on the pads or rotors. Sounds like you've bedded them in, but I might try it again before tearing into it, you don't have much to loose at this point.

If that fails, I'd re-check the shims.

Do your new pads have a 'lead-in chamfer' (usually on both leading, and trailing edge of he pads) ? If yours only have one chamfer, make sure you didn't install the chamfer in the trailing edge position.

I've used his red goop on the backs of some stubborn bakes pads that wouldn't quiet down, I forget what it's called, "Brakequiet" or something, smear it on, let it dry before re-assembly.
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Old 10-11-2018, 12:05 AM   #9
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Well, I have no idea what changed, but on my third test drive after sitting all night, suddenly the noise is gone. I don't know why, but it seems to be ok now. What I do know is it really freaked me out thinking I had done something wrong. I was once a state of California licensed brake mechanic (back when they did those sort of things) and I never had that happen. Oh well, all's well that ends well. One thing I did notice though, is that the pistons don't completely cover the brake pads. That's to say, the outside diameter of the piston is larger than the distance from the top to the bottom of the brake pads, resulting in about 10% of the piston face not touching anything. Anyone ever see that before?
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Old 10-11-2018, 01:06 AM   #10
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I thought your brake chatter would work itself out, glad to hear it! I couldn't think of anything that would cause that other than just wearing itself in over time. I think I've had that happen on the old Jeep after a brake job - fixed it by turning up the radio...
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