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#1 (permalink) Old 05-11-2006, 12:29 PM
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Diagnosing Brake Squeal

Even with all the threads concerning brake squeal on this forum, I'd like to offer my detailed symptoms for opinions on the matter:

After a recent pad and rotor change, the front passenger wheel squeals under the following conditions:

1) Only with light pedal pressure. No squeals at medium or heavy pedal pressure.

2) Squeals only after the car has been driven for a bit (10-15 minutes). For example, no squeals when I first start the car and come to a stop at the bottom of my first hill.

3) On right hand turns while braking it is most pronounced.

I know the anti-rattle clip is in place and I'm using Pagid pads, which are supposed to have an integral anti-squeal backing (no, I did not use anti-squeal compound). My Bentley manual is leaning me towards a wheel bearing, given the increase in sound while braking on a right-hand turn, but I would think a bad wheel bearing would make a fairly consistent squeal, braking or not.

Thoughts on the matter?
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#2 (permalink) Old 05-11-2006, 02:26 PM
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It MAY be an early sign of wheel bearing failure, but I would double check everything brakes wise first (being since they were just done) better to start with what you know and move frome there. I've had wheel bearings come into the shop making all kinds of noises from constant to sparatic loud to soft squeel to grinding gravel kinds of noises...let us know what ya find!

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#3 (permalink) Old 05-12-2006, 07:03 AM
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i favour that this is pads. USE THE GOO on the back of the pad. don;t let it get out of the pad area, but i found this really works.

i do not have much experience (not a mechanic), but i had two bearings fail in my lifetime. always a rumble, NEVER intermittent, that noise is always there. also, worst at 50-65 mph.
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#4 (permalink) Old 05-13-2006, 11:28 AM
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It's your pads and rotors. You need to use BMW's OEM rotors, not aftermarket. Also, BMW's pads a 100% ceramic. Most of your aftermarket pads contain some percentage of metallic compound. It is this characteristic that gives you a squeal at light braking pressures, and after driving, the heat build up in the brakes combined with fresh dust will cause a squeal.

It's a bit more expensive, but worth it. It's quiet, and the car stops better and evenly. You have the EXACT same issue I had with my '99 323i, along with many other customers in the past. There is not enough 'goo' in the world to prevent squeal from non-ceramic pads.

Replace BMW brakes with BMW brakes. I guarantee this will solve your problem.

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#5 (permalink) Old 05-14-2006, 12:29 AM
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Quote:
Originally Posted by 441tech
It's your pads and rotors. You need to use BMW's OEM rotors, not aftermarket. Also, BMW's pads a 100% ceramic. Most of your aftermarket pads contain some percentage of metallic compound. It is this characteristic that gives you a squeal at light braking pressures, and after driving, the heat build up in the brakes combined with fresh dust will cause a squeal.

It's a bit more expensive, but worth it. It's quiet, and the car stops better and evenly. You have the EXACT same issue I had with my '99 323i, along with many other customers in the past. There is not enough 'goo' in the world to prevent squeal from non-ceramic pads.

Replace BMW brakes with BMW brakes. I guarantee this will solve your problem.

441tech
Agreed !
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#6 (permalink) Old 05-15-2006, 08:13 AM
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Thanks for the opinions and advice. However, ponder this:

I changed my rear pads 3,000 miles before I changed my front pads and rotors. After changing the rear pads (not rotors), I experienced no noise. After changing front pads with rotors, I experience the noise (seemingly all from one wheel).

If this was an issue of the pads or the rotors as parts themselves, I would have expected this to occur with the rear wheels as well. Since this is only occuring on one front wheel, I question whether it's parts related. When I get the chance, I'll take the wheel off and have a look at the parts again... maybe something was off.
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#7 (permalink) Old 05-16-2006, 07:27 AM
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well.

as 441tech says, some pads/rotors combinations will squeel like stuck pigs no matter what. i have such an absurdly loud combination on purpose: this is as he says due to a very high metal content of the pads (hawk hp plus), which increases the hot pad friction coefficient so my brakes will pull my eyes out when stomped on (i wear glasses to prevent this).

it may be that your pads are like this, and in such a case, you are screwed.

however, given that it is only one wheel, i think you shoudl consider goo. the other source of squeel at light pedal pressures is the vibration of the pad itself against the backing, inside the caliper. goo makes the pad stick to the backing, and presto, no noise! try it, costs you 40 minutes and 5 cents.
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#8 (permalink) Old 05-16-2006, 07:28 AM
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oh, this is especially true of aftermarket pads, which occasionally are not cut exactly to the shape of the caliper bracket, causing more vibration.
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