Quote:
Originally Posted by ChiefM
Master mechanic here. Still waiting on my 24 M850i to delivered. Have been a Porsche guy and Mercedes guy since my early 30s, before then was a poor Honda and Acura kid. Needless to say, I do all my own work. 2020 with 3500 miles? Ok let me brake this down.
The squealing you hear is one of 3 things. Foreign object (think small rock) between brake pad and rotor, the brake pad vibrating at high frequency, or a wear indicator. Let me explain the last two. When brake pads are installed all guide pins in floating calipers are lubricated, and anti squeal compound is applied to the back of the brake pads. The anti squeal is essentially a light glue, some manufacturers use shims and a soft backing on brake pads to prevent the use of anti squeal. These statements apply to the rear brakes of the 8 series. The front brakes are fixed 4 piston calipers. The brake pads come with adhesive on the back. This adhesive is effectively the anti squeal. Your car is 4 years old. Regardless of mileage, dirt, grime, salt all work their way in and unstick the pads. I am not saying the bmw tech is right, it’s not normal, but if these are original pads, hate to say it but yeah this is to be expected.
Another possibility is that the 8 series doesn’t have brake wear sensors on all 4 corners. This is a common cost cutting measure these days, even in high end cars. What this means is a brake pad is squealing because it’s about to ruin a rotor, on a wheel without a brake pad sensor.
Anyways, from a blue collar guy who ended up being more successful than he ever thought he would be, this is my advice to you.
Go to harbor freight, get a jack and some jack stands. Make friends with a mechanic and inspect your front and rear pads inboard and outboard pad on each wheel. If thickness is good on all four corners, feel your rotors from the inside of the machined face to the outside. It should feel smooth with no lip on the outside edge. If you grooves or waves, this points to a foreign object embedded in your brake pad. If all looks good, remove your rear calipers and grease the pins and apply anti squeal compound to the back of your brake pads. If you still have a squeal, replace your front brake pads as you can not apply anti squeal to them.
Hope this helps.
Chris
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Hey Chris,
Thanks so much for this detailed explanation! It's by far the most comprehensive response I've gotten about the brake squealing.
Your breakdown of the different causes, especially the explanation of anti-squeal on the front vs. rear brakes, makes perfect sense. I really appreciate you taking the time to write all this out.
The mechanic says my front brakes are causing the squeak, but they still have 6mm of pad left. I'll wait to replace them until they're more worn and consider using non-OEM brakes then.
Thanks again, Chris! Appreciate your insights!