Grinding brakes Options

[Mattattack]

So I've been hearing some metal on metal grinding while braking AND while in motion, I figured it was brake pads grinding into the rotors so I put some new rotors and pads on. While the old rotors were warped, even after i put the new ones on the sound is still there if not worse after spinning the wheel while the car was on jacks. could a wheel bearing or caliper be the culprit? Any knowledge would be greatly appreciated.

[Tigawoods]

front or rear?

[Langing]

I assume you are hearing the scraping sound at the front wheel, since you replaced pads (disc brakes), and likeky have either drum brakes or comb. drum/disc on rear, and since you could hear the sound when spinning the tire by hand (on jack stands).

I've just gone through something similar, and it took a while to figure it out. Let me tell you what my problem was so you can check and eliminate first.

A few years ago, my wife had driven the car into a curb; not such a hard swipe but bad enough to cause the only bolt left holding the passenger side motor mount to break, letting the motor fall an inch or so. I fixed that problem, but what I didn't realize was that the hit had bent the 'ears' on the steering knuckle which the caliper mounting bracket mate with. Recently, I decided to replace or rebuild all brake parts, and so put on new everything. When I tried to put the car back in service there was a very loud 'metal on metal' scraping sound that I hadn't heard before.

The additional thickness of the new rotor and pads combination (on rt front wheel) showed up the problem. The lower edge of the mounting bracket was rubbing against the rotor, eating into the rotor surface. You have to remove the tire and just the caliper to be able to see if this is happening. The rotor ought to be perfectly centered in the space inside the caliper mounting bracket, but my rotor was actually rubbing against the inside metal front edge of the bracket. It was doing that because the mounting ears on the steering knuckle were bent.

People here pretty much ALL told me that the knuckle is made of cast iron, and cast iron does't bend. Don't believe them. Whatever steel the knuckle is made from can, and does bend. I located six other examples of bent ears on various car forum websites. If you have kinda-sorta brushed up against a curb at some point in the car's lifetime, yours might be bent, and it is extremely hard to prove to yourself that those ears are actually bent. The best way is to examine the relationship between the rotating rotor and the caliper mtg bracket. When the rotor is scraping, it makes a mark around one surface of the rotor, which provides a second way to know if this is the problem.

If your problem is a bad wheel bearing, put you car on jack stand and spin the tire while holding your hand on the coil spring of the strut. If it is bad, you will feel the vabration in your hand. You might have to be under the car to do that, but it works.

Another possibility is that your wheel's major dust cover (which is attached to the knuckle by four torx bolts) could be bent and is rubbing against the rotor. The clearance with the back of the rotor is small, and since it is at the back, it is a little hard to see, but not hard to check.

Try those suggestions and if none of them are your problem, let me know and I will do some more thinking. Good luck!

[Mattattack]

The problem is on the rear passenger side. Thanks so much for the in-depth explanation, I'm going to test that wheel bearing and dust cover now and see if i can't rule those out before anything else. Would it just be a faint vibration in the coils or something much more noticeable?
I can also take pics if that would help.

[Tigawoods]

It could be the ebrake shoes grinding on the inside of the rotor hat. I had that issue for a while.

[Langing]

The problem is on the rear passenger side. Thanks so much for the in-depth explanation, I'm going to test that wheel bearing and dust cover now and see if i can't rule those out before anything else. Would it just be a faint vibration in the coils or something much more noticeable?
I can also take pics if that would help.

So, you have the disc/drum brake configuration on your rear? My 94 just has drums on the rear, so I haven't seen how the rear caliper attaches, but suppose it's much like the front, except the rear wheels are fixed so aren't used to steer.


The vibration due to a bad wheel bearing is readily noticeable by your hand holding onto the coil spring (not faint) when the tire is rotating freely. And, while you are doing that test, you can be listening to where the sound is coming from if not a bearing failure.

BTW: How loud is the noise?

[Langing]

It could be the ebrake shoes grinding on the inside of the rotor hat. I had that issue for a while.

How did you know your ebrake was grinding? And what caused it to do that?

I've sometimes driven my 2000 Tacoma pickup without releasing the ebrake (never for long) and it didn't seem to make noise; hardly knew it was dragging.

[Tigawoods]

He has a GT so he has discs.


Removing the rear rotors can be a pain and sometimes the ebrake shoes will grip onto the inside of the rotor hat (even when the ebrake is disengaged). You have to rotate the adjustment screw through a hole on the rotor hat. When trying to pull my rotors off (and them refusing to come off) I more than likely stretched the retaining springs that hold the shoe to the face of the dust shield, which in turn made them stick out a bit and rub up against the rotor.

that was the first time I had touched brakes. It was a learning experience.

[Langing]

He has a GT so he has discs.


Removing the rear rotors can be a pain and sometimes the ebrake shoes will grip onto the inside of the rotor hat (even when the ebrake is disengaged). You have to rotate the adjustment screw through a hole on the rotor hat. When trying to pull my rotors off (and them refusing to come off) I more than likely stretched the retaining springs that hold the shoe to the face of the dust shield, which in turn made them stick out a bit and rub up against the rotor.

that was the first time I had touched brakes. It was a learning experience.

Now I understand. Can be a pain. . . slight understatement.

My drum brakes have the same stupid (black) hole in back into which you insert two screwdrivers and pretend to manipulate the adjuster to loosen the pressure of the shoes against the inside of the rotor hat (drum). My first time experiencing that got me so mad (or gun-shy) that the next time I did it, I was prepared with mirrors, super LED flashlights, extra help, etc. to make sure I could get the drums off.

Later on, I learned that I could also use the two bolt holes that penetrate the drum from the front, and now my drums seem to yield easily to carefully ratcheting bolts into them (sometimes with some hammering). But. . . not that long in the future, when rust has accumulated. . . back to the little back door.

I would be surprised if you didn't have similar bolt holes in your rotor hats.

Finally, someone said that initially adjusting your drum brakes after a complete rebuild (with all new hardware) was a tricky competition between where you initially set your adjuster (not all the way in as the BGB says; about a quarter inch out from that point) and how tight you set your ebrake. At one point, I crawled under and traced the ebrake cables from the cabin all the way to the parking brake lever inside the drum, to make sure there was no possible problem in it, because ebrake actions were slightly different between left and right wheels. Turns out, sometimes aftermarket parts are not exactly perfect fits, so that initial adjustment advice came in handy.

Now that I have Betsy back on the road with all new stuff at the wheels, including bearings, ball joints, and tie rod ends, she runs ever so smoothly. Oh, that's also because I worked hard to get the front rotor run-out down to 0.0004" and 0.0007" (R/L), which is well below maximum (0.0020").

[Mattattack]

The sound isn't that noticeable when in motion but it's still there, when I brake it's loud enough for me to notice even with my windows rolled up. I feel like the best way to describe it would be the sound two metal knives would make rubbing together, a metallic scraping of sorts, haha

[Langing]

The sound isn't that noticeable when in motion but it's still there, when I brake it's loud enough for me to notice even with my windows rolled up. I feel like the best way to describe it would be the sound two metal knives would make rubbing together, a metallic scraping of sorts, haha

There is a little metal spring-like thingy built into most of today's pad pairs (one per pair) that's used as a mechanical indicator to tell you when it is time to replace your pads. It's sound is so high-pitched, like a 'squeal.' that I cannot hear it, nor can my brother (BTW: we are NOT Click and Clack ). We both depend on our wives to tell us when they start hearing that squealing sound of the metal thingy scraping around a small width of the rotor. I don't think this is your problem because you said you changed the pads.

Let me ask, however, did you change the rotors and pads on all four wheels, or just the one you think is causing the sound? There are certain sounds in a car that confuse the listener so much they may think it is coming from the rear when it is actually coming from the front, and vice-versa.

When you said you could hear the sound when the car was on jack stands and you rotated the tire, I assumed you heard that sound coming from the wheel you mentioned, but wanted to be certain I was not assuming too much.

Another thing that can go wrong with disc brakes is the 'slider pins' (two bolts without threads that are greased and slide in holes in the caliper mounting bracket) set to permit the caliper to move (slide) on them in such a way that the caliper can grab both pads at roughly the same time with the same force. These 'slider pins' sometimes seize in their holes so the caliper cannot slide. I know this can lead to uneven wear on the two pads. I don't know whether it causes a metallic sound though.

Also, disc brakes are notorious for causing various kinds of noises, so when you change out rotors and pads, you have to make sure you have a good set of shims and mounting bracket pads, and that all of that is suitably greased with caliper grease to dampen "expected" brake noise. Sorry, but I don't know how those sounds sound, so can't be of much help there, except for making you aware of the problem.

You might have to go through the entire process of elimination!

Have you had time to check the dust deflector yet?