Roaring noise

[BIMMERGUY91]

Hey guys,

So when I slow down I get kind of a roaring noise. I assume it is from the brakes I have tried to just roll down the street to a stop and see if it made the noise and I didnt hear anything. I had read that the drill holes in the rotors can get clogged up with carbon so I cleaned them out and it made no difference. Is there something wrong with my brakes or is this normal for these brakes? I have taken it in to BMW to try and get them to fix it twice and they said there was nothing wrong with my brakes and they even took out an M3 they had on the lot and they said it did the same thing.

Anyway whats your take on it?

[Finnegan]

As our tires have aged (and been exposed to many a track day) there's definitely a bit of an increase in what might be described as a "roar" from say 30 to zero when applying the brakes. After swapping out the tires with some newish (1,000 mile) "winter" tires, that have more than 4-5/32 of tread remaining, the noise seems to have diminished a bit.

In any case, I'd say this is "normal", as it does it on my car (even with new rotors and Stoptech street performance pads), and it does it on the wife's Z4M (stock rotors, Stoptech street performance pads).

This little bit of noise has been there as long as I can remember, and the brakes haven't ever been an issue in terms of stopping power on street or track. We have very large floating and drilled rotors, and just as with the drivetrain (clutch, etc.) there's going to be more noise associated with a high-performance vehicle like the ones we drive.

[Kgolf31]

It's the brakes, it's perfectly normal. I thought someone was wrong as well, but the drilled rotors just make noise at high speeds

[Finnegan]

Originally Posted by Kgolf31

It's the brakes, it's perfectly normal. I thought someone was wrong as well, but the drilled rotors just make noise at high speeds

Tire noise I'm describing is incidental then, and probably a contributor, not the main cause.

[BIMMERGUY91]

ok cool i just wanted to make sure what I was hearing was normal. I figured that it was due to the drilled rotors because of the rapid gas expansion in the drill holes. I thought it was tires at first too as mine needed to be replaced but I put brand new tires with an alignment on and it didnt change.

[RobertRO]

Just for the peace of mind, you may want to check out your front hub bearings.
Although quite unlikely, the sound you describe may be related to the bearings.

My Z4MC needed a set of new front bearings at only 30,000 miles, and the symptom was just a roaring sound from around 20 to 40 mph.
With the new bearings the roar disappeared.

[BIMMERGUY91]

Wouldnt that also happen on acceleration too though? Mine is only on deceleration. My friends wheel bearings went out on the front of his mustang and it was just always loud and roaring

[RobertRO]

Originally Posted by BIMMERGUY91

Wouldnt that also happen on acceleration too though? Mine is only on deceleration.

Right, it would also happen on acceleration and cruising. If your is in deceleration only, the bearings are ruled out.

[BIMMERGUY91]

yeah mine is only when braking. I still think I will have BMW check my bearings though since my car is still in warranty

[BIMMERGUY91]

Well finally got around to having BMW check the car over. After initial inspection the wheel bearings and brakes both checked out but the tires are cupped a little bit. Sucks too because they only have about 7000 miles on them and I got them aligned by BMW the day I got the tires. Anyway I took the head tech out for a ride in the car to show him the loud roaring noise I was experiencing. Got the car up to about 100 and then braked fairly hard and the loud roaring noise presented itself to him. We got back to the dealer and he took it back in the shop and it turns out my front passenger side brake rotor was out of spec. So new rotors and pads are being installed on the front today along with a 4 wheel alignment. I will let you know the results