Ringing Brakes... What's Causing It?
 

You can barely hear it when the car is driving in the open, but when driving along a wall or building, the echo of the sound is very clear to me driving and I'm sure it can be heard by people whom I drive by, particularly when braking to a stop. It is a very high pitch sound, which I think is best characterized as "ringing." The car is going in for an oil change tomorrow night - should I mention it to the dealer?

more than likely just brake dust build-up. there's a ton of threads about the sqeaking brakes. mine did the same thing and the dealer just pulled the pads, cleaned them and reinstalled them and it's fine.

Its just a brake thing, dust etc get caught up and cause the noise.

If its REALY loud your pads need changing.

It's a very high frequency sound that changes only slightly as the wheel speed changes. I don't think I'd characterize it as "squealing."

The dealer checked the ringing and confirmed essentially what everyone's been saying. He says that the pads are not very soft (as they once were when asbestos was used), and that the metal used in the pads actually can make them ring slightly.

Get out there and bed those pads in. Run it up to a good speed and jam on the brakes. It'll clear it up. :)

It will take more than one good stop to get the brakes hot enough to put a transfer layer of pad material evenly across the entire surface of the rotors. Follow these instructions and your squealing (or "ringing") problem should go away. Read them carefully before starting. It's very important not to come to a complete stop, lest you bake a pad impression onto the hot rotors and end up with a vibration problem.

http://www.zeckhausen.com/bedding_in_brakes.htm

One question:

If the brakes need to be 'bedded', how come most of us are getting the noise fater thousands of miles? Shouldn't we have had the squeaky/noise problems from day one?

Tha'ts a very good question. The squealing is a high frequency fluttering of the brake pad and requires just the right amount of input and brake force to start up. It's like taking a moist finger and running it around the rim of a fine crystal glass. It will "sing", but only if the right amount of pressure is applied and there isn't too much liquid in the glass to damp out the vibrations. Squeaking brakes take just the right combination of conditions and those conditions aren't always present. It could be that it only happens after a certain amount of pad material wears away or after the bonding agents that hold the pad material together have finished outgassing. I'm not sure exactly.

On Saturday, I'll be attending a brake frcition seminar in Los Angeles, taught by a 35 year veteran of the brake pad manufacturing industry. I'll be sure to pose the question and let you know if I learn anything interesting.

"Outgassing" and a cool metaphor? I haven't enjoyed a post so much since someone explained that the problem with rotary fuel economy is the "thermodynic inefficiency of igniting an oblong volume." I love this forum!

All I know is that I know I often "sing" after outgassing. I'm sure that's it. ;)