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Old 09-03-2004, 08:54 AM
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Wheel clunking and brake squeal

For about the last month my Chevelle is making a bad brake squealing most of the time when I come to a stop. Another noise started about the same time, which is a clunking coming from the front driver's side wheel when I hit bumps in the road. The reason I mentioned the clunking is because I think the brake squeal is related to it. I say this because the pads and rotors are only about a year old. I took the pads off and inspected them, and looked at the rotor to see if maybe a rock might have been stuck between the rotor and pad. Didn't notice anything like that and there is still quite a bit of pad left.

What might be causing this? And does anyone think the two might be related? What should I check out as far as the clunking goes?

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Old 09-03-2004, 09:55 AM
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There are several things that can clung in the suspension.

1. Ball joints.

2. Shocks.

3. Control arm bushings.

The brake pads are probably "glazed" use some sandpaper on them to break the glaze.

Do they have the warning squeaker tab on them that tells you they are worn out.

Troy

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Old 09-03-2004, 10:10 AM
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The pads have plenty of material left on them. Someone also told me about the glazing so I took the pads off and scuffed them and the rotors up lightly with some very fine grit sandpaper. This did not help either.

Would a worn spindle cause this clunking? Also, if the spindle was worn enough could it also be casuing enough vibration to make the brakes squeal?
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Old 09-03-2004, 10:26 AM
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The only thing that will wear on the spindle, is the wheel bearings worn out and the race spin on the spindle. I would think that would be a continuous noise. Jack it up and spin the wheel, if there is a bad bearing you will hear it. You might try a new set of pads for the squeaking.

Troy

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Old 09-03-2004, 02:27 PM
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Also a loose pad can cause both a rattle and/or a squeal. The rattle would normallty disappear when brakes are applied if it is brake related.

If they are GM calipers, the outer pad should be cinced to the caliper by its ears, and should not move. The inner pad clips to the piston to hold it. Some type of anti-squeal (shim and/or lubricant or adhesive) can be used on pad backings where they contact the caliper/piston to absorb some high pitch noises as well.

Some pads just like to squeal, and are just inferior. The clunk is what you really need to find before driving again.
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Old 09-03-2004, 03:07 PM
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Put a jack under the lower a arm, as close as you can get to the wheel, raise it a few inches, take a long extension or some sort of lever, and put under the tire and lift to see if there is any slack in the ball joints.

Troy


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Old 09-03-2004, 05:47 PM
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Quote:
Originally posted by yesgo

Also a loose pad can cause both a rattle and/or a squeal. The rattle would normallty disappear when brakes are applied if it is brake related.

If they are GM calipers, the outer pad should be cinced to the caliper by its ears, and should not move. The inner pad clips to the piston to hold it. Some type of anti-squeal (shim and/or lubricant or adhesive) can be used on pad backings where they contact the caliper/piston to absorb some high pitch noises as well.

Some pads just like to squeal, and are just inferior. The clunk is what you really need to find before driving again.


This man has it. If the tabs have not been bent to hold them tight to the caliper housing, you will experience pad knock (GM disease) as the pad actually slides with the rotor on brake application until it hits and is stopped by the caliper housing.
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Old 09-03-2004, 06:51 PM
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Hummmmm, never heard of that. I've seen them come into the shop without any clips and not make any noise. If it wanted to slide or move with the caliper, the little clips would not stop it.

Just my thoughts.

Troy

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Old 09-03-2004, 08:59 PM
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It is in every shop manual i have ever read pertaining to brakes, and I have done it on thousands of vehicles. Many Dodge and Ford pads are like that too. Sure, they move with the caliper... they have to. They are not supposed to move independantly of the caliper, or caliper bracket, thus the need for the clips and/or ears, varying according to design. If they are not cinched down on a GM, it is not a guaranteed rattle/squeak, just a possible one. If you show me a type of disc brake system which has no provisions for keeping the pad from rattling, it will be a new one on me, after several thousand brake jobs on domestic and foreign vehicles.

I also may have misspoke a statement. If it is a rattle over bumps that is pad related, it should disappear when the brakes are applied... and there are always exceptions.
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Old 09-03-2004, 10:19 PM
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Quote:
Originally posted by yesgo
Sure, they move with the caliper... they have to. They are not supposed to move independantly of the caliper, or caliper bracket, thus the need for the clips and/or ears, varying according to design. If they are not cinched down on a GM, it is not a guaranteed rattle/squeak, just a possible one. If you show me a type of disc brake system which has no provisions for keeping the pad from rattling, it will be a new one on me, after several thousand brake jobs on domestic and foreign vehicles.
I'm not understanding just what you are saying.

Your other post read like you were saying the pads moved with the rotor until they stopped and that would make a clunk.

The pads ride on the rotor, there are two long bolts that hold them in place. The only way they can move is to clamp the rotor between them. If they are loose, there is something else wrong.

I understand the clunking noise to be going down the road and hitting bumps. which my first guess would be a bad ball joint. A shock would thump and rattle, but would not be a clunking noise.

You can modify the pads if they are solid surfaced, by taking a hack saw or cut off and cutting a grove a third of the way from each end of the pad top to bottom, about 1/2 of the way through the pad. This was in a service bulletin from GM in the early 70s.
I have done it many times and it works.

Troy

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Old 09-04-2004, 01:12 AM
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*sigh*
I agree the front end needs to be checked.
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Troy,
The pads do not actually ride against the rotor at all times... at least without any kind of force. That is definitely not how they work. If they are working correctly, there will be a minute space between the pad and rotor while driving. You may hear or feel a very slight drag on inspection. There is way more to it than I can easily explain...

On this type of GM front disc (most 69-87 RWD GM), the inner pad is secured to the piston by a clip. The piston retracts when the brake is released, bringing the inner pad with it, away from the rotor. The action of the 'square cut' seal retracts the piston. The caliper will move in the opposite direction, but not enough to cause an inner pad drag.

The outer pad is secured/cinched to the caliper. The holes around the guide pins may help, but are mostly an installation guide.

The caliper uses oring bushings to float on the guide pins and sleeves. When the piston moves outward, it pushes the inner pad to the rotor. As the inner pad pushes against the rotor, this resistance forces the rest of the caliper to slide inward, applying the outer pad, and giving the squeezing action. All of this happens in an instant.

When the brakes are released, and operating properly, everything returns to very near its previous position. This is accomplished with the 'square cut' seal against the piston, and the o-ring bushings on the guide pins returning to their original shape, as well as the rotor itself pushing the pads away as it spins and flexes on the bearings. It is not a perfect system, but there should be no real drag.

Pad rattle, squeal, or click, sometimes can occur on this type of brake if the inner clip is missing, or the outer pad is not cinched. You may get a single click when changing from reverse to drive, and applying brakes at both times, or the brake pads can actually rattle in place over bumps.... or they may just squeal... or you may notice nothing. I would not describe it as a clunk, but people describe things differently.

If there is excess runout in the rotor, it can affect this, without causing a shake. If there is anything holding pressure to the piston, that can also affect it. If the orings are worn or dry.... or the pins are bent, or, or, or.....

This is already too long, and has barely scratched the surface of a proper explanation. On the later 'low drag' calipers, there is, well, even less drag. This is accomplished with a different cut to the piston seal, and a different type of master to compensate for that.

If you wish to discuss this further, Troy, I would suggest a separate brake discussion post, although I usually dislike arguing (and typing, though you can't tell by this), or you can PM me. I may ask your advice on some body work i need to do, and you can ask me how to fix your brakes so they dont drag if you like. I'm sure I dont know everything about brakes, but I know quite a bit. I have my opinions, and I have facts with references. I merely mentioned the outer pad cinch because it is often overlooked, and sometimes can cause a problem such as described. If you have never heard of it, you have not seen or cured as many brake problems as I, as I am sure I have not done many of the things of which you are an expert. When it comes to brakes, I am an expert, certified and specialized. I often avoid these posts as I find it difficult to argue with bad advice, or to advise people with no brake knowledge or comprehension, as well as pre-conceived myths. Even on brakes, I am not always right, or entirely accurate, but I am seldom wrong if you take my words for what they are... of course, you will need excellent reading comprehension skills, as I am not the best at articulating my thoughts. They are too involved.
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Anything that I would personally describe as a clunk over bumps, I would also suspect to be front end parts. All of my brake inspections include suspension, steering, and bushing inspections.

I have heard clicks described as clunks, or far worse. Grinds are squeals, squeaks are horrible grinding, grinding is air escaping. The noise from the right front is descibed as the left rear, the horrible shaking described is barely noticeable, while the completely unnoticed shake puts my knee in my chest, and half twists my wrists off. Descriptions are just a loose guide, and it makes it even more difficult in type. I have even heard what I would call a very slight drag, as "considerable resistance". It is relative.

Last edited by yesgo; 09-04-2004 at 01:18 AM.
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Old 09-04-2004, 06:23 AM
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Our rattles and clunks do not have the same definition.
But thats kool.



There is no need to explain to me how brakes work. I have been a certified GM master technician since 1966. And still have an automotive repair shop with 5 techs. I have worked on one or two brake systems.

Troy

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Old 09-04-2004, 12:08 PM
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Thanks for the excellent ideas guys! I'm going to take my car into the suspension shop just as soon as I can get ahold of McGard locks. I seem to have bad luck every once in a while, and my key to get my wheel locks off is warped. This is because the last time I had my car in the shop the mechanic torqued all the lug nuts (including the locks!) to 100 ft/lbs! I guess this is alright for the lug nuts but definitely not the locks. Needless to say, when I went to take my wheels off here a while back I could not get the locks off and the key deformed in the process. So, now I must someone how figure out how to get a replacement key (I don't have the ID number anymore) from McGard.


Anyways, I'll let you guys know what I find out about the frontend. And as far as the brakes go I'm just going to try a different set of pads.


Before I go though, I just ran out to the garage while writing this and looked at something with my pads. I noticed the outter pad on the side that's squealing has quite a bit of play in it; I can move it up and down and left and right really easily with my hand. That's not normal is it?
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Old 09-04-2004, 12:49 PM
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No it's not. if they are that loose the wheel should spin easly.
And you would have a rattle.

BUT how did you do that with the wheel locked on?

Troy
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Old 09-04-2004, 12:52 PM
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Quote:
BUT how did you do that with the wheel locked on?
I have 17" Cragars and I can reach between the spokes and get right at the caliper. I assume this is what you're asking?
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