New pads and rotors -- "whirling" sound when braking?

[tgb1974]

I had new OE rear pads and rotors installed on my 2016 F83. Indy shop did an outstanding job and cleaned everything thoroughly including the calipers. Anyway the car now makes this weird “whirling” sound when depressing the brake pedal. It’s not a squeal or anything like that. And the stopping power is great. (I replaced the lines with stainless steel lines from ECS.)

I have read that this sound is normal with new pads and rotors and goes away after a while, but I want to ask you fine folks. Thanks.

[M3SQRD]

Cross drilled rotors can make a whirling sound but I’m surprised you hear it with only a rear brake service. Do you hear the noise with the windows up? It should get quieter with more mileage/bedding in.

[tgb1974]

Originally Posted by M3SQRD

Cross drilled rotors can make a whirling sound but I’m surprised you hear it with only a rear brake service. Do you hear the noise with the windows up? It should get quieter with more mileage/bedding in.

Yes, it sounds like a turbine winding down. Exactly like this guy heard in his new M4 (start at the 6:15 mark):

https://youtu.be/a_MfJElYmlg?si=y6-3G704RD-f88vu

[tgb1974]

Update: This morning I drove the car on the expressway at higher speeds and then on side roads at lower speeds, for probably a total of 50 miles. At first the turbine sound was present as before when braking. But after a while, it disappeared completely. Maybe it was just a break-in/bedding issue?

[tgb1974]

Originally Posted by tgb1974

Update: This morning I drove the car on the expressway at higher speeds and then on side roads at lower speeds, for probably a total of 50 miles. At first the turbine sound was present as before when braking. But after a while, it disappeared completely. Maybe it was just a break-in/bedding issue?

Further update: after a expressway speed drive, the turbine sound is less noticeable but still there, especially when almost coming to a complete stop. Thoughts?

[tgb1974]

Originally Posted by M3SQRD

Cross drilled rotors can make a whirling sound but I’m surprised you hear it with only a rear brake service. Do you hear the noise with the windows up? It should get quieter with more mileage/bedding in.

It has now been about 250 miles since the new rotors and pads where installed. The sound is much less noticeable now but is still there, especially when slowing to a complete stop. Also, with reference to the picture, the wear pattern is not circular, like my front or old rear rotors. Is that normal or indicative of an installation error? Thanks.

[M3SQRD]

Originally Posted by tgb1974

Update: This morning I drove the car on the expressway at higher speeds and then on side roads at lower speeds, for probably a total of 50 miles. At first the turbine sound was present as before when braking. But after a while, it disappeared completely. Maybe it was just a break-in/bedding issue?

Originally Posted by tgb1974

Further update: after a expressway speed drive, the turbine sound is less noticeable but still there, especially when almost coming to a complete stop. Thoughts?

Originally Posted by tgb1974

It has now been about 250 miles since the new rotors and pads where installed. The sound is much less noticeable now but is still there, especially when slowing to a complete stop. Also, with reference to the picture, the wear pattern is not circular, like my front or old rear rotors. Is that normal or indicative of an installation error? Thanks.

The whirling sound will continue to lessen with more mileage. Looking at your most recent picture, it looks like very little pad transfer has occurred. Has most of your recent mileage been highway mileage? I’d recommend doing 6 hard stops (without engaging ABS) from 60-20 mph in quick succession and then drive for 15-20 minutes ideally without using the brakes. This will allow the pad material to be transferred uniformly to the brake rotor surface.

The repeating cross-hatched marks on the rotor surface are machining marks leftover from the manufacturing process. They’ll be there for a while especially on rear rotors. This is normal and will wear away with mileage.

[tgb1974]

Originally Posted by M3SQRD

The whirling sound will continue to lessen with more mileage. Looking at your most recent picture, it looks like very little pad transfer has occurred. Has most of your recent mileage been highway mileage? I’d recommend doing 6 hard stops (without engaging ABS) from 60-20 mph in quick succession and then drive for 15-20 minutes ideally without using the brakes. This will allow the pad material to be transferred uniformly to the brake rotor surface.

The repeating cross-hatched marks on the rotor surface are machining marks leftover from the manufacturing process. They’ll be there for a while especially on rear rotors. This is normal and will wear away with mileage.

It has now been ~500 miles since I had new rear pads and rotors installed. The whirling sound is not as bad as it was at first. I have noticed, however, that my brakes sound like what you hear from about 14:35 to 14:38 in this video:

This guy is slowing down after being on the track (though his brakes appear to be new). My car makes this sound when applying the brakes at street speeds. Is that normal? Sorry for the repeated questions, I just want to make sure that there is not anything wrong.

[M3SQRD]

Originally Posted by tgb1974

It has now been ~500 miles since I had new rear pads and rotors installed. The whirling sound is not as bad as it was at first. I have noticed, however, that my brakes sound like what you hear from about 14:35 to 14:38 in this video:

This guy is slowing down after being on the track (though his brakes appear to be new). My car makes this sound when applying the brakes at street speeds. Is that normal? Sorry for the repeated questions, I just want to make sure that there is not anything wrong.

The whirling/humming sound? That’s all I hear, and I’ve listened twice, unless I missed it. It’s caused by the holes in the rotor. It’s typically worse when you first install new rotors and pads because there can be a lip, albeit small, that can amplify things. The 500 miles - were they more highway miles with little braking or more side streets with frequent stops from 50 or 45 mph? Also, the rear brakes only provide ~25% of the braking so they take considerably more mileage before they fully wear in. Furthermore, it depends on how hard you’re applying the brakes; e.g., slowly dragging the brakes to stop the car from 45 mph is barely using the brakes vs. quickly stopping from 45 mph, so-called late braking, with the brakes applied at 75+% of their capability which is more heavily using the brakes. The sound also gets quieter as the holes get packed full of brake dust. That noise is always there when using rotors with holes and, generally, it gets to the point where you don’t notice it. Try more aggressively braking for the next ~50 miles and see/hear what happens. The last picture of your rotors that you posted showed no pad transfer (still looked like bare iron), have they started to turn a more darker gray yet?

[tgb1974]

Originally Posted by M3SQRD

The whirling/humming sound? That’s all I hear, and I’ve listened twice, unless I missed it. It’s caused by the holes in the rotor. It’s typically worse when you first install new rotors and pads because there can be a lip, albeit small, that can amplify things. The 500 miles - were they more highway miles with little braking or more side streets with frequent stops from 50 or 45 mph? Also, the rear brakes only provide ~25% of the braking so they take considerably more mileage before they fully wear in. Furthermore, it depends on how hard you’re applying the brakes; e.g., slowly dragging the brakes to stop the car from 45 mph is barely using the brakes vs. quickly stopping from 45 mph, so-called late braking, with the brakes applied at 75+% of their capability which is more heavily using the brakes. The sound also gets quieter as the holes get packed full of brake dust. That noise is always there when using rotors with holes and, generally, it gets to the point where you don’t notice it. Try more aggressively braking for the next ~50 miles and see/hear what happens. The last picture of your rotors that you posted showed no pad transfer (still looked like bare iron), have they started to turn a more darker gray yet?

Thank you for your thorough response! Yes, I was referring to the sound when he applied the brakes like a turbine slowing down--like a progressively slowing whirling. I did not know that this sound was caused by the drilled rotors. My old rotors (which I think were original to the car with close to 50k miles on them) did not make a similar noise--at least not as far as I could tell. I will follow your advice on braking more aggressively. The rotors do not look any different at this point.

[M3SQRD]

Originally Posted by tgb1974

Thank you for your thorough response! Yes, I was referring to the sound when he applied the brakes like a turbine slowing down--like a progressively slowing whirling. I did not know that this sound was caused by the drilled rotors. My old rotors (which I think were original to the car with close to 50k miles on them) did not make a similar noise--at least not as far as I could tell. I will follow your advice on braking more aggressively. The rotors do not look any different at this point.

Misha would have commented on the whirling noise if it was out of the norm. That noise was dominated by the front brakes but the rears also contribute to the overall sound level. Turn your radio up louder until the noise is gone

[tgb1974]

Originally Posted by M3SQRD

Misha would have commented on the whirling noise if it was out of the norm. That noise was dominated by the front brakes but the rears also contribute to the overall sound level. Turn your radio up louder until the noise is gone

Thank you very much -- I appreciate your insight on this!

[M3SQRD]

Originally Posted by tgb1974

Thank you very much -- I appreciate your insight on this!

You’re welcome

Try rebedding the pads if the rotor surface(s) still looks shiny and still has machining marks. Rotors should look like this when fully bedded with a uniform layer of brake pad material:

[tgb1974]

Originally Posted by M3SQRD

The whirling/humming sound? That’s all I hear, and I’ve listened twice, unless I missed it. It’s caused by the holes in the rotor. It’s typically worse when you first install new rotors and pads because there can be a lip, albeit small, that can amplify things. The 500 miles - were they more highway miles with little braking or more side streets with frequent stops from 50 or 45 mph? Also, the rear brakes only provide ~25% of the braking so they take considerably more mileage before they fully wear in. Furthermore, it depends on how hard you’re applying the brakes; e.g., slowly dragging the brakes to stop the car from 45 mph is barely using the brakes vs. quickly stopping from 45 mph, so-called late braking, with the brakes applied at 75+% of their capability which is more heavily using the brakes. The sound also gets quieter as the holes get packed full of brake dust. That noise is always there when using rotors with holes and, generally, it gets to the point where you don’t notice it. Try more aggressively braking for the next ~50 miles and see/hear what happens. The last picture of your rotors that you posted showed no pad transfer (still looked like bare iron), have they started to turn a more darker gray yet?

Here is what the rear rotors look like after about 600 miles of mostly normal braking and driving activity. Thoughts?

[M3SQRD]

The rotor surface looks like it’s showing a nice uniform pad transfer layer. However, the presence of the machine marks still showing on the rotor surface suggests they still aren’t fully bed-in even with 600 miles. Have you done any of the bed-in techniques? Are they still making the whirling sound?

[tgb1974]

Originally Posted by M3SQRD

The rotor surface looks like it’s showing a nice uniform pad transfer layer. However, the presence of the machine marks still showing on the rotor surface suggests they still aren’t fully bed-in even with 600 miles. Have you done any of the bed-in techniques? Are they still making the whirling sound?

Thank you for the response. I have several times driven to ~60 mph and then braked hard. Brakes feel great but I didn't want to push it.

And yes, the whirring sound is still present, especially when braking (and even decelerating without braking!) at low speeds, approaching a complete stop. I took it to the dealer and had the shop foreman drive the car around. The foreman said the sound I'm hearing now is most likely something with my winter tires, probably an uneven wear issue, and suggested that I wait until I swap to my summer tires and see if the sound ceases at that point.

Considering that I hear this sound when decelerating without braking at all and that the sound changes with the rotational speed of the wheels, his theory seems plausible to me. The winter tires (Michelin Pilot Alpin PA4) have plenty of tread on them with no observable problems, but the fronts (where the sound is most noticeable) are a bit dated now, with 2018 and 2019 date codes. Maybe the tires are starting to harden (or something) which is causing this sound...?

Thoughts? Thanks!

[M3SQRD]

Originally Posted by tgb1974

Thank you for the response. I have several times driven to ~60 mph and then braked hard. Brakes feel great but I didn't want to push it.

And yes, the whirring sound is still present, especially when braking (and even decelerating without braking!) at low speeds, approaching a complete stop. I took it to the dealer and had the shop foreman drive the car around. The foreman said the sound I'm hearing now is most likely something with my winter tires, probably an uneven wear issue, and suggested that I wait until I swap to my summer tires and see if the sound ceases at that point.

Considering that I hear this sound when decelerating without braking at all and that the sound changes with the rotational speed of the wheels, his theory seems plausible to me. The winter tires (Michelin Pilot Alpin PA4) have plenty of tread on them with no observable problems, but the fronts (where the sound is most noticeable) are a bit dated now, with 2018 and 2019 date codes. Maybe the tires are starting to harden (or something) which is causing this sound...?

Thoughts? Thanks!

If you’re hearing it when the brakes are not applied then sound is from a different source. When we put out winter wheels on there’s definitely a rhythmic rumbling/humming sound which changes with speed. I agree with the foreman, it’s the tire noise that you’re hearing, not the brakes.

Like I said, your rotors now appear to have a uniform transfer layer of pad material but there’s still a small amount of manufacturing marks still visible. The marks are not a concern but completing one full bedding-in procedure should eliminate them. However, it’s definitely safe to fully use your brakes now and I’d recommend doing at least five 60 mph to 20 mph repeated stops in quick succession. Then drive for 15-20 min without using the brakes (e.g., drive on the highway). This will finish the bedding-in of your brakes. Don’t worry about having to heavily apply your brakes at this point because you have a sufficient pad transfer layer so the rotor surface is protected.

[tgb1974]

Originally Posted by M3SQRD

If you’re hearing it when the brakes are not applied then sound is from a different source. When we put out winter wheels on there’s definitely a rhythmic rumbling/humming sound which changes with speed. I agree with the foreman, it’s the tire noise that you’re hearing, not the brakes.

Like I said, your rotors now appear to have a uniform transfer layer of pad material but there’s still a small amount of manufacturing marks still visible. The marks are not a concern but completing one full bedding-in procedure should eliminate them. However, it’s definitely safe to fully use your brakes now and I’d recommend doing at least five 60 mph to 20 mph repeated stops in quick succession. Then drive for 15-20 min without using the brakes (e.g., drive on the highway). This will finish the bedding-in of your brakes. Don’t worry about having to heavily apply your brakes at this point because you have a sufficient pad transfer layer so the rotor surface is protected.

Thank you very much for this advice. In your experience, do winter tires cause increasing road noise as they get older and presumably harden? I do not recall these tires causing this level of road noise in the past, so I am at a loss as to why this is happening now.

[M3SQRD]

Originally Posted by tgb1974

Thank you very much for this advice. In your experience, do winter tires cause increasing road noise as they get older and presumably harden? I do not recall these tires causing this level of road noise in the past, so I am at a loss as to why this is happening now.

Absolutely! As the tread blocks wear done, winter tires continue to get louder and it starts to sound like a pickup truck with giant off-road tires. I always replace winter tires before their tread blocks hit the wear bars.

[tgb1974]

Originally Posted by M3SQRD

Absolutely! As the tread blocks wear done, winter tires continue to get louder and it starts to sound like a pickup truck with giant off-road tires. I always replace winter tires before their tread blocks hit the wear bars.

Thanks for this. I will post updates in this thread and after I switch to my summer tires.

[M3SQRD]

Originally Posted by tgb1974

Thanks for this. I will post updates in this thread and after I switch to my summer tires.

You’re welcome

I always look forward to the switch back to summer performance tires! However, we keep an e92 M3 on summer performance tires so on a decent winter day with no salt on the roads, we can take it out for a fun few hour drive.

[N1rve]

Originally Posted by tgb1974

It has now been about 250 miles since the new rotors and pads where installed. The sound is much less noticeable now but is still there, especially when slowing to a complete stop. Also, with reference to the picture, the wear pattern is not circular, like my front or old rear rotors. Is that normal or indicative of an installation error? Thanks.

I am guessing you are not the original owner of the car lol. When my F82 was brand new with 19 miles, it had these marks. Eventually went away after like 2000 miles or so.