Hi guys,

Now that it's getting colder out, the sound is getting louder. I got some Stoptech slotted/drilled rotors put on an all four corners and also PosiQuiet ceramic pads on all four corners like 6 months ago.

When I drive my car after it's been sitting for a while, it sounds like the rotors are warped and the pads are stuck to the rotors, making a weird vibration/humming sound. Any ideas on what this could be?

 

ez, it is a noted problem with the slotted/drilled rotors that especially when cold or during very hard braking, the brakes can make a whirring type of sound. Is this the sort of sound that you are hearing? I have also noticed with the newer pads, that if you have the e-brake set and let the car sit for a few days, the pads will stick to the rotor and will "snap" during the first movement of the vehicle. Then sometimes you will also get a slight ticking sound where you are breaking off the high spots that this causes. But, after say 2-3 seconds of medium breaking, this noise goes away.

 

Slotted/drilled rotors and pads have a specific break-in cycle that must be done before normal usage. If it was not done correctly, you might have slightly warp the rotors and they will need to be turned.
I do all repair work on my vehicles and I did a shortcut on my Durango during the Break-in that caused the rotors to warp. Took them to "O'rielly to be turned, they are fine now.
Dependent on where the pads/rotors where installed, they should have completed the break-in.

 

I just installed drilled/slotted rotors with ceramic pads.
What is this specific break-in cycle?
Mine tend to be super good for the first few brakes, then return to normal.

 

In short terms:
Do a series of 10 decelerations from 30 mph to 15 mph, at 15 - 30 seconds apart.
Next, a series of 10 decels from 45 mph to 15 mph, at 15 - 30 apart.
A series of 3 -5 decels from 60 - 15 mph at 45 seconds apart.
Then drive/brake gently for a few hundred miles.
your brakes will smell and make noises during the bedding process.

Note: perform this bedding-in process on a vacant road, other drivers might call the cops


Check the website for your specific brand, they should have "Bedding" procedures listed for warranty specs.