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Old 7th October 2005, 15:17   #1
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Default About Squealing Brakes

Hi,

Considering that there are different causes for brakes making an annoying squealing noise (yes, painful enough to compare it to the chalk on the blackboard trick!), i was wondering if we can have some kind of technology (maybe it already exists) that will analyze the sound and pinpoint the problem. OR if there were an alternative way to drive the car and figure out based on the handling + sound that would be even better! I agree the easiest thing is to just yank the brake assembly out and give a look-see!

I have given whatever reasons that i know of below in order to cause the brakes to squeal:
1. Excessive brake pad wear
2. warped rotors
3. misaligned calipers (back of the brake pad)
4. loose calipers
5. loose wheel bearings
6. incorrectly sized pads (unnecessary friction)
7. glazed pads or rotors
8. sticky pistons

Interestingly, the magnitude of the sound is generally revealing but it is normally coupled with the speed you were braking at. I have read articles in the past that also point at cars that do sonar analysis especially in the BMWs.

Always appreciate your comments,
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Old 13th February 2015, 13:07   #2
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Default Squealing brakes!

Hello

I fitted new brake-pads (Make: Reynold??) to my car two months back. The car has since driven more than a 1000 kms. However, the brakes still squeal a lot. The Garage advised to change the calipers as well. Does a worn-out calipers result in squealing or is it the brake-pad itself?

Please advise.

Regards
Ashok

Last edited by aah78 : 13th February 2015 at 19:27. Reason: Post edited. Spacing.
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Old 13th February 2015, 16:04   #3
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Default Re: Squealing brakes!

Its difficult to know the exact problem just by reading the symptoms but let me go at this in a logical sense - were the brake pads replaced because they had run their limit? Was the whistling sound there before replacement? If no then that means the whistle has developed after replacement. Brake calipers do develop malfunction but it has its symptoms apart from a squealing noise- if there's a detectable smell caused by friction heat or if the car is shaky and pulls to either direction when braking then for sure calipers are the culprit.

Mostly every brake pad needs time to settle in, but 2 months of driving seems to be long enough. Another possibility of whistling sound could be rust formation across the edge of the discs. This can be easily diagnosed when the tyre is removed as a rusty shade can be clearly seen and felt over the border. If so sanding the same with emery paper will take care of the squeal (personal experience).

Of course one must always be careful when dealing with things such as brakes or steering so you could take a 2nd opinion from an authorised station or a reputed garage. Most car problems always have symptoms, still a car that is over 3-4 years old with over 40k kms in Indian conditions can develop any problem imaginable. If the 2nd opinion is the same then go ahead with the replacement.

Last edited by dark.knight : 13th February 2015 at 16:25.
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Old 13th February 2015, 16:29   #4
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Default Re: Squealing brakes!

Quote:
Originally Posted by Ashokkp View Post
Hello

I fitted new brake-pads(Make- Reynold??) to my car two months back. The car has since driven more than a 1000 kms. However, the brakes still squeal a lot. The Garage advised to change the calipers as well. Does a worn-out calipers result in squealing or is it the brake-pad itself?

Please advise.

Regards
Ashok
Did you use the proper anti-squeal compound on the back of the pads before installing them?

For example:

http://www.autopartswarehouse.com/br...paste~pop.html
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Old 13th February 2015, 16:41   #5
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Default Re: Squealing brakes!

Hello All

The original pads did squeal a lot and had considerable worn. I am not sure where anti-squeal compound was used; If not, can it be applied now?

There is no tell-tale smell and the car is neither shaky nor pulls in either direction. It is just the high pitch squeal. It really creates quite a racket inside the cabin.

Regards
Ashok
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Old 13th February 2015, 17:40   #6
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Default Re: Squealing brakes!

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Originally Posted by Ashokkp View Post
Hello All

The original pads did squeal a lot and had considerable worn. I am not sure where anti-squeal compound was used; If not, can it be applied now?

There is no tell-tale smell and the car is neither shaky nor pulls in either direction. It is just the high pitch squeal. It really creates quite a racket inside the cabin.

Regards
Ashok
If the brakes are working okay otherwise except the squealing, just pull the pads to put the anti-squeal compound on the back, and make sure each pad goes back in the same place and orientation from where it was removed. If there are any shims, please make sure they are clean, straight and clear of rust before re-installing.
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Old 13th February 2015, 18:45   #7
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Default Re: Squealing brakes!

Just put some water on the pads and drive....very carefully...and brake. Does the squeal remain?

If yes then pads are not the issue. If no...
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Old 13th February 2015, 19:15   #8
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Default Re: Squealing brakes!

Hello

This reminds me of the day the pads were changed, the brakes failed (only once) at slow speeds. I took the car back and they bled the brakes and I have been driving around (at expressway speeds also) without any incident. Now, should i be worried or shall I just "treat" the squeals?

Last edited by aah78 : 13th February 2015 at 19:28. Reason: Post edited. Spacing.
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Old 13th February 2015, 20:41   #9
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Quote:
Originally Posted by Ashokkp View Post
This reminds me of the day the pads were changed, the brakes failed (only once) at slow speeds. I took the car back and they bled the brakes and I have been driving around (at expressway speeds also) without any incident. Now, should i be worried or shall I just "treat" the squeals?
Are the pads wearing out evenly?

Squealing I guess could be due to metal-to-metal contact during braking.

Remove the pads and rub it with emery paper once. Refit and see if the squeal repeats?!
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Old 13th February 2015, 22:21   #10
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Quote:
Originally Posted by VCheng View Post
Did you use the proper anti-squeal compound on the back of the pads before installing them?



For example:



http://www.autopartswarehouse.com/br...paste~pop.html

This is really relevant. Squealing is very rarely coming from the pad on the rotor. Its nearly always the pad in the caliper and thats why you need to apply the anti squeal paste!

Jeroen
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Old 14th February 2015, 02:45   #11
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Default Re: Squealing brakes!

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Originally Posted by Jeroen View Post
This is really relevant. Squealing is very rarely coming from the pad on the rotor. Its nearly always the pad in the caliper and thats why you need to apply the anti squeal paste!

Jeroen
Squealing is merely a very high frequency vibration that is set up by metal to metal contact when the pads are forced against the rotors. A thin layer of a sticky compound that does not melt away at high temperatures is enough to dampen them, eliminating or greatly reducing the vibrations and hence the squeal.

This is assuming that the original diagnosis is correct. The fact that the brakes "failed once" after the repair and required a re-bleeding to put right does not create much confidence in the quality of the work done.
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Old 14th February 2015, 08:24   #12
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Default Re: Squealing brakes!

Go to an authorized Hyundai dealer, get a full brake service & OEM pads. They have a special high temperature non petroleum grease to lubricate the brake pins. After their service you should have noise problems. I suspect the squealing is due to the inferior quality of the pads combined with lubrication issues.
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Old 14th February 2015, 18:03   #13
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Default Re: Squealing brakes!

Quote:
Originally Posted by VCheng View Post
... A thin layer of a sticky compound that does not melt away at high temperatures is enough to dampen them, eliminating or greatly reducing the vibrations and hence the squeal.
....
A layer of sticky compound where? The pads do wear out. Hence, I guess there is no use putting it there.
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Old 14th February 2015, 18:25   #14
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Default Re: Squealing brakes!

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Originally Posted by dhanushs View Post
A layer of sticky compound where? The pads do wear out. Hence, I guess there is no use putting it there.
The anti-squeal compound is applied on the back of the pads, between the backing plate and the caliper contact points. There is nothing applied between the front of the pads between the friction surface and the rotor.
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Old 14th February 2015, 21:49   #15
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Quote:
Originally Posted by VCheng View Post
The anti-squeal compound is applied on the back of the pads, between the backing plate and the caliper contact points. There is nothing applied between the front of the pads between the friction surface and the rotor.

Yes, correct and sometimes you have to, but very carefully, apply a tiny bit on the sides of the pad where it touches the caliper
Jeroen
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