Brake vibration, noise

[SimonS4MTM]

Took my car for a hard drive today, and was very hard on the brakes a few times.

When releasing the brakes after a hard application there was a very loud noise and vibration.

I do have small cracks at the holes on the discs and i am presuming that as the disc expands with heat, these cracks open and catch on the pads, making the noise and vibration.

When making the noise and i apply the brakes, the noise stops.

Can anyone confirm my theory for me?

[jonno1]

I think I had something similar but would happen when pulling away from standing (i.e. after braking). I took it to Dovercourt Audi and let this South African speed freak mechanic thrash my car up and down their little test alley ("I really like these S4s") and then he basically explained it was due to a build up of brake dust and the pads sticking a bit and oscillating (his word, not mine) against the disc, once moving again, the noise went. Basically something to do with the S4 having so many brake pads and them rubbing a little.

Completely gone now so whether that was the case I dont know! Not changed the pads or the discs!

[UKS4APR1]

It will be uneven pad deposits on the disc. i.e. bits of melted pad material fused to the surface of the disc.

Read this Link:
http://www.stoptech.com/whitepapers/war ... s_myth.htm

[DavidR]

Simon.

I had something very similar on OEM discs when they became checked (small cracks radially in the surface of the disc)

Fine when it was cold, but as the disc heated up there was a very noticeable vibration and "hum" from the brakes, mainly during use, rather than just after.

Shortly afterwards there was a massive vibration as the disc had cracked through.

[SimonS4MTM]

It will be uneven pad deposits on the disc. i.e. bits of melted pad material fused to the surface of the disc.

Read this Link:
http://www.stoptech.com/whitepapers/war ... s_myth.htm

I dont think it is this as it only happens once the brakes are released, not when they are applied.

It sounds more like jonno's sugestion