[stueyyy]

Originally Posted by Tag

What tires did your car come with?

Michelin PS4S, but I did change to Kumho WP72s for the winter.

Tires are noticeably noisier (like most winter tires), but this whine seems distinct from that. And like I mentioned, the whine immediately went away if I went off-throttle or put it in neutral.

[Tag]

Originally Posted by stueyyy

Michelin PS4S, but I did change to Kumho WP72s for the winter.

Tires are noticeably noisier (like most winter tires), but this whine seems distinct from that. And like I mentioned, the whine immediately went away if I went off-throttle or put it in neutral.

Thanks, I was just curious is you had the same tires as the OP to see if there was any correlation.

[aerobod]

Originally Posted by BIGW0RM

Yup. I can always try and or I’ll just go to an independent shop. But now that another member has heard it, I feel much better! Lol.

Have you also tried swapping the tyres from side to side? Uneven wear patterns and the start of cupping of the tread can cause resonance at some speeds (it could well come back at twice the speed that it currently occurs at).

A side-to-side swap can alter the noise volume or how it changes with throttle position, as the slightly worn tread blocks will be pressed to the road differently.

[BradMX5]

Not sure if your sound matches this at all but he has a video of the sounds from the outside as well as inside and it seems to be consistent with a certain speed as well. Could very well be something to do with your drive shaft.

[BIGW0RM]

Originally Posted by stueyyy

Michelin PS4S, but I did change to Kumho WP72s for the winter.

Tires are noticeably noisier (like most winter tires), but this whine seems distinct from that. And like I mentioned, the whine immediately went away if I went off-throttle or put it in neutral.

Ive got Pzeros. less than 2k miles. And two alignments now. I dont think its tires. If I had to guess, its one of these things.

drive shaft
diff
electronic feedback of some sort
maybe fuel pump

Or just a normal characteristic of the car that only you and I have caught on to yet. Im praying its that! Or active sound.

Another thing I noticed. The radiator fan spins down when I come to a stop. The spin down of the fan when I come to a stop sounds pretty simular to the sound we are hearing. I wondered if the radiator fan was boosting itself when on light throttle between those speeds. But the sound sure does seem to be coming from right behind me so I dont think its that.

But its driving me nuts not knowing what it is. But I sure do feel better knowing Im not the only one who hears it.

[Crazyotter]

Maybe it’s humming because it doesn’t know the words…

Ok I’m leaving I’m sorry. That was my dad joke for the day 😁

[AZG87]

Originally Posted by Crazyotter

Maybe it’s humming because it doesn’t know the words…

Ok I’m leaving I’m sorry. That was my dad joke for the day 😁

Lol. Also at your handle. I had a client who let otter.ai run loose in their M365 environment instead of going Copilot as recommended and now they are having a helluva time.

[carlos916]

I think it was asked before but have you had your break in service?

The sound reminds me of diff noise.. common on e60 M5's and with a fluid change its fixed..

keep us updated!

[BIGW0RM]

Originally Posted by carlos916

I think it was asked before but have you had your break in service?

The sound reminds me of diff noise.. common on e60 M5's and with a fluid change its fixed..

keep us updated!

Yes. Break in done at 900 miles. I’ve heard this sound since day one. I assumed it was the diff and thought the service fixed it. But I was wrong. It’s still there.

[jmg]

Just throwing this out there but maybe it’s exhaust related? You mentioned you have a valve controller. Are your valves completely open? Try closing it and see if it affects the noise.

I’ll try replicating on my auto 2025 tonight to see if I hear anything as well.

[BIGW0RM]

Originally Posted by jmg

Just throwing this out there but maybe it’s exhaust related? You mentioned you have a valve controller. Are your valves completely open? Try closing it and see if it affects the noise.

I’ll try replicating on my auto 2025 tonight to see if I hear anything as well.

Thanks man. Yes I have a controller. Open or OEM mode makes no difference. Engine mode makes no difference.

Basically once I hit 62mph. I hear a hum. Whirl like hum. Turn your exhaust button off. Radio off. Get up to 61 mph and once you hit 62 mph you should hear it.

Just LIGHTLY throttle it on and off above 62mph and you might hear what I’m hearing. It’s purely on light throttle only and specifically starts at 62mph and holds until about 70mph.

[jmg]

Originally Posted by BIGW0RM

Thanks man. Yes I have a controller. Open or OEM mode makes no difference. Engine mode makes no difference.

Basically once I hit 62mph. I hear a hum. Whirl like hum. Turn your exhaust button off. Radio off. Get up to 61 mph and once you hit 62 mph you should hear it.

Just LIGHTLY throttle it on and off above 62mph and you might hear what I’m hearing. It’s purely on light throttle only and specifically starts at 62mph and holds until about 70mph.

Just tried these. I didn’t hear anything out of the ordinary. I’m on P-Zeros as well. Lowered on KWHAS, 15mm spacers all around. No valve controller. 1200 service just completed 100 miles ago. I tried with all drive modes and with the exhaust on and off.

[BIGW0RM]

Took a drive up to Los Olivos in Santa Barbara area and got to spend some time in the car going 62-70MPH for extended periods of time. I had my wife with me and I could clearly hear it. I was able to make it come and go on demand but she could not hear a thin! Yet she can hear me across the house mumbling with attitude under my breath to her...lol!

This hum/whirl I hear is super annoying. I will be brining my car in to the dealer to see what they say.

Im kind of wishing I just paid up for the BMW HAS over the KW HAS now. Because if it is a diff or drive axle, I know the dealer is going to immediatly blame my KW drop. Ugh. This sucks!

[aerobod]

Originally Posted by BIGW0RM

Took a drive up to Los Olivos in Santa Barbara area and got to spend some time in the car going 62-70MPH for extended periods of time. This hum/whirl I hear is super annoying. I will be brining my car in to the dealer to see what they say.

Im kind of wishing I just paid up for the BMW HAS over the KW HAS now. Because if it is a diff or drive axle, I know the dealer is going to immediatly blame my KW drop. Ugh. This sucks!

What alignment values have you got with the KW HAS? If you are lowered and camber has increased, using the stock BMW alignment specs may cause uneven tyre wear that can cause a treadblock resonance in quite a low number of km. If the camber has increased without changing the toe to compensate as far as possible, inner tyre wear could be accelerated, leading to tread blocks that will hum quite nicely.

[BIGW0RM]

Originally Posted by aerobod

What alignment values have you got with the KW HAS? If you are lowered and camber has increased, using the stock BMW alignment specs may cause uneven tyre wear that can cause a treadblock resonance in quite a low number of km. If the camber has increased without changing the toe to compensate as far as possible, inner tyre wear could be accelerated, leading to tread blocks that will hum quite nicely.

Im not sure. I had the dealer align it and my local wheel shop the 2nd time. My car is 2K miles old now and has done this since day one. Its purely based on on or off very light throttle. If I lift off gas it immediatly stops. So it cant be tires. Tires would hum regardless of throttle input.

[aerobod]

Originally Posted by BIGW0RM

Im not sure. I had the dealer align it and my local wheel shop the 2nd time. My car is 2K miles old now and has done this since day one. Its purely based on on or off very light throttle. If I lift off gas it immediatly stops. So it cant be tires. Tires would hum regardless of throttle input.

Sometimes tyres will "hum" differently depending on on throttle, off throttle or braking. If it didn't do it before the KW install and lowering, I wouldn't rule out the alignment or tyres completely.

[aerobod]

Originally Posted by BIGW0RM

Here is a better clip with a noise canceling microphone. It kills most of the other in car sounds, but you can clearly hear the hum like noise I am hearing. Its NOT this loud in the car. This mic just picked it up much better.

https://www.youtube.com/shorts/dv8K2XkbPNk

I did a basic spectrum anslysis of the repetitive sounds in this video. The main energy is around 150 and 220Hz, but there is also some energy around 550Hz. I’m not sure why the sound comes and goes, unless that was a function of how it was recorded, and/or the way noise cancelling was done.

With the auto 3.154 diff and stock rear tyres with 777 revs per mile, the 13/41 pinion/crownwheel teeth would have a tooth frequency of 549Hz at 62mph (13.4Hz wheel rotation frequency) and 619Hz at 70mph (15.1Hz wheel freq). Actual speed is probably about 2mph less than BMW dash indicated speed.

The diff side bearings probably have about 20 taper rollers or ball bearing in them that will rotate at about half shaft speed, so about 1/4 of the pinion tooth frequency, so about 137Hz at 62mph.

The hum could be from the diff, as the rotating parts frequency is not too far off the 550Hz and 150Hz measured frequencies, but I’m not sure what the 220Hz frequency would correlate to, although the nose bearings balls could be around that frequency, as they are more likely to be about 8 balls rotating at 3.154 times as fast as the side bearings, so perhaps 173Hz at 62mph.

[jmg]

Originally Posted by aerobod

I did a basic spectrum anslysis of the repetitive sounds in this video. The main energy is around 150 and 220Hz, but there is also some energy around 550Hz. I’m not sure why the sound comes and goes, unless that was a function of how it was recorded, and/or the way noise cancelling was done.

With the auto 3.154 diff and stock rear tyres with 777 revs per mile, the 13/41 pinion/crownwheel teeth would have a tooth frequency of 549Hz at 62mph (13.4Hz wheel rotation frequency) and 619Hz at 70mph (15.1Hz wheel freq). Actual speed is probably about 2mph less than BMW dash indicated speed.

The diff side bearings probably have about 20 taper rollers or ball bearing in them that will rotate at about half shaft speed, so about 1/4 of the pinion tooth frequency, so about 137Hz at 62mph.

The hum could be from the diff, as the rotating parts frequency is not too far off the 550Hz and 150Hz measured frequencies, but I’m not sure what the 220Hz frequency would correlate to, although the nose bearings balls could be around that frequency, as they are more likely to be about 8 balls rotating at 3.154 times as fast as the side bearings, so perhaps 173Hz at 62mph.

This guy sciences!

[BIGW0RM]

Originally Posted by aerobod

I did a basic spectrum anslysis of the repetitive sounds in this video. The main energy is around 150 and 220Hz, but there is also some energy around 550Hz. I’m not sure why the sound comes and goes, unless that was a function of how it was recorded, and/or the way noise cancelling was done.

With the auto 3.154 diff and stock rear tyres with 777 revs per mile, the 13/41 pinion/crownwheel teeth would have a tooth frequency of 549Hz at 62mph (13.4Hz wheel rotation frequency) and 619Hz at 70mph (15.1Hz wheel freq). Actual speed is probably about 2mph less than BMW dash indicated speed.

The diff side bearings probably have about 20 taper rollers or ball bearing in them that will rotate at about half shaft speed, so about 1/4 of the pinion tooth frequency, so about 137Hz at 62mph.

The hum could be from the diff, as the rotating parts frequency is not too far off the 550Hz and 150Hz measured frequencies, but I’m not sure what the 220Hz frequency would correlate to, although the nose bearings balls could be around that frequency, as they are more likely to be about 8 balls rotating at 3.154 times as fast as the side bearings, so perhaps 173Hz at 62mph.

Wow! Most impressive!

The recordings audio would come and go due to the external microphone not picking up cabin noise unless I was on the gas. So the silent parts are me off the throttle. When the audio picks back up, that was me on the throttle lightly.

It’s for sure coming from the rear of my car. If I move my head forward I can’t hear it. I’m just pissed I lowered my car thinking this sound had left and all was good.

It’s gunna be a uphill battle getting my dealer to help me now.

I sincerely thank you for the most educational post I’ve ever seen here. Thank you!

[jmg]

Originally Posted by BIGW0RM

Wow! Most impressive!

The recordings audio would come and go due to the external microphone not picking up cabin noise unless I was on the gas. So the silent parts are me off the throttle. When the audio picks back up, that was me on the throttle lightly.

It’s for sure coming from the rear of my car. If I move my head forward I can’t hear it. I’m just pissed I lowered my car thinking this sound had left and all was good.

It’s gunna be a uphill battle getting my dealer to help me now.

I sincerely thank you for the most educational post I’ve ever seen here. Thank you!

I'm not sure what dealership you go to, but I took my F80 M3 CS into the dealership for a rattling even though it was lowered and they managed to find the source and fix it under warranty. It wasn't the diff, but some kind of mount under the vehicle. I believe they have to prove that the part is directly causing the warranty claim.

[aerobod]

Looking at frequencies for the side bearings more closely, I can’t find photos of the bearings for the current M2/3/4 3.154 diff, but the prior F87 diff has 21 taper rollers with about a 1.25 shaft-to-roller cage rotation ratio. This would give a frequency at 62mph of 13.4 * 21 / 1.25 = 225Hz, close to the observed 220Hz frequency.

The nose bearings for that diff have 13 balls with a 1.5 shaft-to-ball cage rotation ratio. This would give a frequency at 62mph of 3.154 * 13.4 * 13 / 1.5 = 366Hz, which doesn’t correlate with an observed frequency (but it doesn’t have to be a problem area).

This then leaves the 150Hz frequency unexplained, it is something that is about 11 times the wheel rotation frequency, but is a bit high for the wheel bearing or CV joint resonance (both will be about half that frequency).

[afk84]

I have a humming sound after the cold start cools down and I noticed a humming sound from the engine side