Scratching sound coming from rear rotors

[Matt Brandsema]

Hey everyone. I am working on a 2006 Jeep Liberty and the rotors on the rear of the vehicle (both sides) have what appears to be scratches going around the rotor. It looks as if something got between the pad and the rotor and causes scratching all the way around. The brakes themselves are new, (a year old max) and have plenty of material left on them.

When driving, there is a periodic scratching sound coming from the rear, it is not a continuous sound, but more like it only happens on a certain spot of the rotor. I removed the caliper and rotor and cleaned everything with brake clean and the sound is still there (ruling out foreign material stuck in there) The brakes are a “sombrero hat” design (E-brake is drum brakes but normal brakes are disc brakes). The drum brake part of the rotor is perfectly fine with no scratches.

I am thinking he just needs new rotors from foreign material that got lodged in there. But I wanted to ask people here before I tell him to go buy new rotors. I checked for bad wheel bearings by rocking the tire back and forth, and while there isn’t a noticeable amount of play, I do here a small little “knock” sound when rocking back and forth on each side. Also, the sound gets more pronounced when turning it seems. So I am stuck between “bad rotor” or “bad bearing.”

What do you guys think?

Topic

[Andrew Phillips]

[quote=”Xyius” post=137047]When driving, there is a periodic scratching sound coming from the rear, it is not a continuous sound, but more like it only happens on a certain spot of the rotor. I am thinking he just needs new rotors from foreign material that got lodged in there. [/quote]

Sounds like the rotor has a bit of runout (warp). A machine shop can check it, and perhaps turn it down on a brake lathe. That would resurface the gouges also.

I checked for bad wheel bearings by rocking the tire back and forth, and while there isn’t a noticeable amount of play, I do here a small little “knock” sound when rocking back and forth on each side.

Is this a 4WD? Is there the same play when you shake the wheel with your hands at 9 and 3 o’clock as there is when they are at 6 and 12? Does the wheel turn smooth? Usually a bearing won’t make a knocking sound unless there is significant play. You may be feeling/hearing axle shaft end play or some kind of movement in the suspension. How do the tires look? Any cupping, feathering, or uneven tread wear?

What do you guys think?

Start with resurfacing/replacing the rotor and see what happens. I can’t say whether the wheel bearing is good or bad based on this conversation, but it is probably unlikely.

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