A metallic snap when accelerating / low speeds

[NoSuchSol]

New to the family here - '16 M3 w/ Comp Pack.

After the cars been warmed up (best I can tell), at low acceleration from a stop there is a snapping noise that may happen once or twice. It doesn't continue while driving but will happen during stop and go.

The description of the sound: Similar to a card in the spokes; or perhaps a heat shield that's moving/cracking upon acceleration.

Anyone else have this sound before? I'm not sure it's worth addressing with the dealership since it doesn't feel mechanical, but don't know if I should be concerned.

Side Note: Had to emergency brake and the next time I had to come to a stop had a vibration noise from the front drivers side. Didn't do it again and no noticeable damage or oddities on the pads, rotors, wheels, or tires. Freaked me out though... helped to remind me to give more space behind trucks when you can't see in front of them or if they're even paying attention to what's ahead (which he wasn't - would have been my fault had I bumped him).

[D675PDX]

Doesn’t sound exactly the same as what you’re describing but possibly...there’s a shield behind the brake rotors that rocks/gravel will get caught in and grind against the rotors that can make anywhere from a slight noise to a god-awful screeching noise depending how lodged in the stone is.

[lukej]

Originally Posted by D675PDX

Doesn’t sound exactly the same as what you’re describing but possibly...there’s a shield behind the brake rotors that rocks/gravel will get caught in and grind against the rotors that can make anywhere from a slight noise to a god-awful screeching noise depending how lodged in the stone is.

I agree, I would check the shields covering the rotors ,, if I remember right there was a service bulletin to fix the covers so they don’t trap rocks in them.. someone will chime in if I’m wrong.

[NoSuchSol]

Thanks - definitely not a screech noise. It sounds like an expansion noise. I'll see if I can get some audio of it. I could see it being a rock lodged well enough into a place that the shield hits against it at low acceleration but never becomes dislodged.

[hellokitty]

Push the brake shields in using a stick. I had a similar noise when upgrading to cup 2s which picked up a bunch of pebbles and lodged them into the brake shields.