[midcont]

Both times brakes get progressively worse with increasing squeal and vibration with use, like warped rotors. Also gets harder to modulate becoming very on/off and where a steady amount of pressure will grab and let go when almost stopped.
Is there a bedding procedure that has to be done?
Anybody know why this is occurring or have a similar issue?

[Mach550]

What are your driving habits? Know I'm not in an M5 but I'm on 2 year old discs and pads close to 40k miles on my M550i with no issues and I definitely do not drive economically.

[italiabrain]

I drive the hell out of my car. I replaced my rear tires well before 10k miles if that gives you any indication.

My brakes have been completely trouble free. I get the occasional squeal when cold, low-speed, and light pressure all line up, but that's it. The stock wheels are open enough that you can roughly gauge the front pads without taking the wheel off and they look like they have a ton of life. They're also completely smooth braking down from 130+

Either you have a defective component or you drive with two feet. If it's all of 4 corners, then a frozen caliper or individual pot doesn't make sense. It's possible you have a more central issue with a master or slave cylinder that is sticking enough to keep contact and heat them up... but 2 rotor replacements before 10k miles something is definitely off.

[midcont]

Well, I don't drive with two feet and the car is used for mostly highway commuting, so in reality the brakes get very little use. I'll find out if the pads are worn but I have definitely not noticed the smell of burning pads when parking in the garage, which would indicate they were rubbing while driving.
A defective component does sounds right, but two sets of rotors and pads in such a short amount of time?
Let me ask the forum this; under braking, is your pedal travel progressive with feel or does it feel very "by wire"? For the time I have owned this car, it's felt very synthetic and electronic if that makes sense. Very much on/off and hard to modulate. Have not experienced this in any other vehicle so don't know if it's inherent to the car or indicative of whatever issue is occurring.

[pcai]

Originally Posted by midcont

Well, I don't drive with two feet and the car is used for mostly highway commuting, so in reality the brakes get very little use. I'll find out if the pads are worn but I have definitely not noticed the smell of burning pads when parking in the garage, which would indicate they were rubbing while driving.
A defective component does sounds right, but two sets of rotors and pads in such a short amount of time?
Let me ask the forum this; under braking, is your pedal travel progressive with feel or does it feel very "by wire"? For the time I have owned this car, it's felt very synthetic and electronic if that makes sense. Very much on/off and hard to modulate. Have not experienced this in any other vehicle so don't know if it's inherent to the car or indicative of whatever issue is occurring.

The M5 brakes have a lot of initial bite, so I can see why it would feel hard to modulate. But I think that the brakes are quite progressive after the initial bite and they provide quite a bit of stopping power. IMO the brakes feel really great, and gives you a lot of confidence when you're hooning the thing. Your situation seems very strange. It doesn't sound like you hammer the brakes a lot, and that's an absurdly low mileage to be replacing pads and rotors 2 times. I would definitely bring it up with your dealer. And yes, my brakes squeal like mad sometimes under light braking, but that's just a part of the experience

[midcont]

Car is being returned today from dealer. They noted no wear on pads but warped rotors. Attributes it to bad metal. But the second time? And nobody else reports issues like this?
Fingers crossed that this is not just going to occur again, and that the weird brake feel it's always had is addressed. Just don't feel good about it.
Is there a special brake beading procedure that is supposed to be followed?

[TheRealBob]

The vibration would indicate warped rotors. I believe the most common cause of warped rotors is over-tightening the wheel lugs. Another is driving through water when the brakes are very hot. Another would be cheap pads that are bonding to the rotors. I assume you had the work done at your dealer, so pads should be good.

Good luck.

[Aronis]

Wow, that is odd. I have 30,000 miles on my original brakes (2018 year) and they are not more than 1/2 worn down. (was very surprised actually, happily). Sorry to hear your trouble. Hope they find the real cause and not just assume it's your foot!

Mike

[spuntyb]

Definitely odd. I drive shit out of my tuned F80, and didn't need pads and rotors until 34k miles. Twice is definitely out of order.

[BMWM5NYC]

Maybe dragging calipers which are over heating the calipers and warping them.

[Fegelein]

Originally Posted by midcont

Both times brakes get progressively worse with increasing squeal and vibration with use, like warped rotors. Also gets harder to modulate becoming very on/off and where a steady amount of pressure will grab and let go when almost stopped.
Is there a bedding procedure that has to be done?
Anybody know why this is occurring or have a similar issue?

I have 17k on mine w/ no signs of wear and I am an aggressive driver. I had similar issues w/ AMG brakes and rotors in the past, which Benz replaced on their dime. You paying???

[midcont]

This is all warranty covered no questions asked.
Got the car back and while the sound and vibration are gone, there is still this very electronic feeling when braking where there is just not smooth modulation. When applying constant light pressure, just before coming to a red light say, the car definitely feels like the brakes are grabbing and letting go just a little bit. Mind you this is at very slow speed. It's not like abs at full lock. Think of when you are coming to a smooth stop at constant speed to the point where you stop without the car jerking forward. This is hard to do. As you slow down to almost stopped it feels like the brakes ever so slightly are grabbing where you want them, and then just a little bit harder for a split second every beat or two. If this were a linear chart imagine small but sudden spikes with low duration interrupting the otherwise smooth line.
Bottom line, we're back to square one which was the same weird brake feel and my assumption we'll end up in the same place in another few k miles with warped rotors. My bigger complaint is the feel though. Dealership does not seem interested in delving into the matter.

[ashmostro]

What percent of your driving is traffic/commuting? Our stock pads are thankfully more aggressive than what you normally find on the average car, but what that also means is that their high-temperature "adherent" mode of friction may start at a higher operating temp than traffic driving can achieve for your pads. If driving in mostly traffic, you could in theory be staying in the low-temp "abrasive" friction mode the entire time which literally is scraping metal off the rotors to create friction and tends to feel a lot more off-on than adherent which is much more progressive.

If your driving patterns can't change due to use case, my only suggestions are to switch to a lower-temp pad like one of those low-dust ceramic style, OR if you don't like the idea of losing performance potential you may want to do a brake bedding exercise every weekend to put on an adherent transfer layer that by the middle to end of the week will end up getting scraped off the rotor but at least for that time you will have a better pedal feel and protect the rotor somewhat.

[midcont]

Originally Posted by ashmostro

What percent of your driving is traffic/commuting? Our stock pads are thankfully more aggressive than what you normally find on the average car, but what that also means is that their high-temperature "adherent" mode of friction may start at a higher operating temp than traffic driving can achieve for your pads. If driving in mostly traffic, you could in theory be staying in the low-temp "abrasive" friction mode the entire time which literally is scraping metal off the rotors to create friction and tends to feel a lot more off-on than adherent which is much more progressive.

If your driving patterns can't change due to use case, my only suggestions are to switch to a lower-temp pad like one of those low-dust ceramic style, OR if you don't like the idea of losing performance potential you may want to do a brake bedding exercise every weekend to put on an adherent transfer layer that by the middle to end of the week will end up getting scraped off the rotor but at least for that time you will have a better pedal feel and protect the rotor somewhat.

Most of my commuting is high speed on highway. I don't think cold temps are the issue here.
If this were the case though, wouldn't I be experiencing poor braking performance in general/when cold vs. the grab/let go feeling I'm getting?
My other car has carbon ceramic rotors and I've never experienced this.

[ashmostro]

high speed doesn't necessarily mean you are using your brakes often enough to warm them up. Remember, the faster you go, the more brake cooling you have. The question is what kind of braking you are doing when you do - slowing slight from 85 to 75? Slowing abruptly from 60 to 20, repeatedly? One will do very little to generate heat while the other will dump a lot and not have as much cooling between braking events.

And no, abrasive friction is often a similar mu (coefficient of friction) to adherent. What it does do that is "low performance" is have more difference in your moving coefficient of friction vs. stopped, which is why it will feel more jerky and harder to modulate.

Look, I'm not saying this is definitely what's happening to you because I can't really confirm without observing the totality of your driving habits myself. But, the symptoms would at least match this hypothesis.

[midcont]

Originally Posted by ashmostro

high speed doesn't necessarily mean you are using your brakes often enough to warm them up. Remember, the faster you go, the more brake cooling you have. The question is what kind of braking you are doing when you do - slowing slight from 85 to 75? Slowing abruptly from 60 to 20, repeatedly? One will do very little to generate heat while the other will dump a lot and not have as much cooling between braking events.

And no, abrasive friction is often a similar mu (coefficient of friction) to adherent. What it does do that is "low performance" is have more difference in your moving coefficient of friction vs. stopped, which is why it will feel more jerky and harder to modulate.

Look, I'm not saying this is definitely what's happening to you because I can't really confirm without observing the totality of your driving habits myself. But, the symptoms would at least match this hypothesis.

I'm decelerating from high speed for EZ pass. Locally I'm coming to a stop at a stop sign or light from 40 mph. Regular driving. I'm not accelerating into traffic only to slam on the brakes to slow down. I'm not coming up to a light, braking late and decelerating as hard as possible.
Not sure what to tell you. I don't treat this car like the brakes have to be warmed up to work smoothly. Do you experience my symptoms when your brakes are cold? This happens to me regardless of the temp anyway.

[Fegelein]

Originally Posted by midcont

This is all warranty covered no questions asked.
Got the car back and while the sound and vibration are gone, there is still this very electronic feeling when braking where there is just not smooth modulation. When applying constant light pressure, just before coming to a red light say, the car definitely feels like the brakes are grabbing and letting go just a little bit. Mind you this is at very slow speed. It's not like abs at full lock. Think of when you are coming to a smooth stop at constant speed to the point where you stop without the car jerking forward. This is hard to do. As you slow down to almost stopped it feels like the brakes ever so slightly are grabbing where you want them, and then just a little bit harder for a split second every beat or two. If this were a linear chart imagine small but sudden spikes with low duration interrupting the otherwise smooth line.
Bottom line, we're back to square one which was the same weird brake feel and my assumption we'll end up in the same place in another few k miles with warped rotors. My bigger complaint is the feel though. Dealership does not seem interested in delving into the matter.

The "electronic" feeling you are mentioning I think is subjective, it depends on what you drove before and also drive in addition. I have a number of cars, from a Classic '84 911 Porsche w/ only slightly assisted braking, to a 458 w/ ceramics! All feel and brake differently. Each car has it's own characteristics, however the wear and rotor issue you mention is a different story.

[ashmostro]

Originally Posted by midcont

I'm decelerating from high speed for EZ pass. Locally I'm coming to a stop at a stop sign or light from 40 mph. Regular driving. I'm not accelerating into traffic only to slam on the brakes to slow down. I'm not coming up to a light, braking late and decelerating as hard as possible.
Not sure what to tell you. I don't treat this car like the brakes have to be warmed up to work smoothly. Do you experience my symptoms when your brakes are cold? This happens to me regardless of the temp anyway.

This behavior and driving style does sound like it could be abrasive friction... No thing's for sure without inspecting but it's a possibility.

Can you take pictures of your rotor surfaces?

[midcont]

Originally Posted by ashmostro

This behavior and driving style does sound like it could be abrasive friction... No thing's for sure without inspecting but it's a possibility.

Can you take pictures of your rotor surfaces?

Well, the rotors were replaced two days ago so I doubt that will show you anything.

[midcont]

Originally Posted by Fegelein

The "electronic" feeling you are mentioning I think is subjective, it depends on what you drove before and also drive in addition. I have a number of cars, from a Classic '84 911 Porsche w/ only slightly assisted braking, to a 458 w/ ceramics! All feel and brake differently. Each car has it's own characteristics, however the wear and rotor issue you mention is a different story.

Agreed, but something with the braking is abnormal here. The question for the forum is what is it, so we can have the dealer look specifically at it.

[ashmostro]

Originally Posted by midcont

Well, the rotors were replaced two days ago so I doubt that will show you anything.

Whoops, yeah. Nix that.

[Fegelein]

Originally Posted by midcont

Agreed, but something with the braking is abnormal here. The question for the forum is what is it, so we can have the dealer look specifically at it.

I think this is a rabbit hole and if you need to get them replaced a 3rd time, you are covered by the lemon law, if that still exists!