2008 E70 Brake Squeak

[B4BMW]

Originally Posted by Marcool

Well, I bought it in November.

Exactly same problem here with my Aug'08 X5 with 4000 miles. Went to dealer (Chicagoland area) and told me that they didn't find anything (what....????) wrong with brakes. Told me that it might be snow/salt issues but not satisfied with their answer. I don't know what they did, but after the visit, I haven't heard the noise for two weeks and then started again...

My 10 year Honda and 4 year Lexus brakes never made any noise in any weather conditions, why is this so called "HIGH END" luxary cannot handle?

[Penguin]

> why is this so called "HIGH END" luxary cannot handle?


It depends on whether you want the quietest brakes or the best performing brakes. If you want quietest, buy a Lexus.

[M6X]

does anyone know the science behind brake squeaks?

[Zoich]

Originally Posted by M6X

does anyone know the science behind brake squeaks?

I thought I explained it clearly in this thread, in Post #2. You have inner and outer brake pads for each rotor. The outer pad is only secured by an anti rattling clip, typcially you need to spray on or dab on these additional tacky goo on the backside of the outer brake pad so it sticks to the caliper. When it gets loose, your brake gets suqeaky because it's lightly rubbing against the roter (no big deal). I will try to find pictures to expain. Someone had said BMW brakes are loud and Lexus is quiet. That's absurd. it has nothing to to with brand, it's simply whether or not the outer pad is loose or not. Typcially the softer the brake pad (lots of dust) will stop the car better. cheap chain shops like Midas or CarX offer life time pads, you can for sure bet on they are hard metallic pads -- they wear off slowly but very poor stopping performance.

Go to www.zeckhausen.com and learn more about brakes. You will understand how simple it is to change your own brake pads and rotors -- it is the biggest scam when dealers charge you 1000 for all four brakes.

[JCL]

Originally Posted by M6X

does anyone know the science behind brake squeaks?

Brake Squeal 101:

If it is a squeal, as opposed to a grinding noise, it is caused by one or both of the pads vibrating in one or more calipers. The pad vibrates due to a harmonic being set up between the pad and the rotor. Surface finish of the rotor can affect it as much as pad composition. That means that a glazed rotor can cause a squeal regardless of the pad hardness or softness. That is also why a few hard applications can change the noise..

Either pad can vibrate and make a noise, inner or outer, in my opinion and experience. There is an antivibration clip on the outer pad (which tensions the pad). That tension shifts the harmonic frequency sufficiently that it prevents noise. Beyond that, the key is that you won't get a noise unless you have a path for that vibration to be transmitted along. That is why the high temperature grease on the pad ears is so critical, it isolates the pad from the caliper and stops the noise being transmitted.

Having a chamfer at the leading edge of the pad can also change the vibration characteristics of the pad, and thus the squealing characteristics.

Hard and soft pad material doesn't impact noise as much as friction characteristics of the pads do. Metal Master pads for example are very hard, but have far less noise than many other pads. BMW puts carbon black in their pads as a filler material, and it helps with damping out noise, but it causes visible black brake dust. That is separate from the issue of whether the pads are considered hard or soft, but it does impact the friction characteristics, and thus the tendency of the pad to vibrate and make a squealing noise.

[B4BMW]

Originally Posted by Penguin

> why is this so called "HIGH END" luxary cannot handle?


It depends on whether you want the quietest brakes or the best performing brakes. If you want quietest, buy a Lexus.

So what you are saying is the "best performing brakes" can make squeaks.
sorry...not a wise answer. I really don't care what the brand is, but the point is to find if this is a well known (and accepted) issue and any fix available from the manufacturer?

[Penguin]

> So what you are saying is the "best performing brakes" can make squeaks.


Yes. You will also find that the pads used by BMW put off excessive amounts of dust. But they have better "feel" than the less dusty ones other manufacturers put on their cars.

But, as I posted a while back, many brake pad squeals result from chronic gentle braking. If you are, as I am, a chronic gentle braker, they try using the brakes more aggressively for a few stops in a safe place. There is a good chance the squeal will go away for a while.

[B4BMW]

Thanks Penguin. I am less worried about X5 brakes than buying a Lexus .

[Penguin]

Please let me know if doing a few aggressive stops eliminates the squeak for you.

[Marcool]

Originally Posted by Penguin

Please let me know if doing a few aggressive stops eliminates the squeak for you.

Well, it's dry now and the squeak is gone. I guess it will be back when it's snowing again then I will see if aggressive stops would help or not. I also have the appointment with the dealer next Wed and I will give you an update.