Brake issue (noise)

[cpolyak]

Looking for some guidance as I'm scratching my head chasing a noise that just crept up this evening after some spirited driving.

 

Noticed a cyclical knocking sound, directly related to speed (faster/more frequent, slower/less frequent), while coming back into neighborhood. Got under car, looked around the drivetrain and found one loose bolt with play in it at the driveshaft to rear differential mount. Tightened it and took a test drive.

 

Now, I'm hearing the cyclical noise only when I apply brakes and it seems to be coming from front end of car. I looked around the rotors/calipers and didn't see anything unusual. The noise begins as soon as I slightly depress brake pedal and continues when I firmly press pedal.

 

Thought I'd ask the peanut gallery if they had any guesses to focus the chase as nothing obvious jumped out at me. The noise wasn't present last time I drove the car, which is even more intriguing. 

 

[Simeon]

Can you feel the feedback through the brake pedal? A pulsing? Does it go away as you push harder on the brakes?

 

Done any brake or bearing work recently?

[yeewiz]

is the cyclical noise frequency same as tire revolution?

 

is the noise metallic?

[AndySals]

Cracked disc?

[cpolyak]

I don't feel feedback in the pedal and the noise seems to be 1/per revolution. The noise is consistent regardless of pressure applied to pedal. Brakes and bearings are new as of 600 miles ago. 

 

Next step is to pull the wheels and look closer at the front disks/calipers. 

[NickVyse]

stone in your tyre :-)

[TobyB]

Bent backing plate.

loose caliper mount.

warped rotor (less likely)

 

.

[Simeon]

Calipers bolts are my guess. Calipers is moving when the run out on the rotor is passing through the calipers. 

 

Internet dude guess. 

[cpolyak]

So I pulled the wheels last night and inspected calipers closely. Everything seemed in order and tight. Went for short test drive and it noise was gone. Strange. 

 

Didn't have time for a longer drive but I wonder if heat buildup from the previous long/spirited drive caused something to expand and rub. I'll dig into it more next weekend. Thanks for the suggestions all.