After changing the brake pads and rotors of my 2006 Buick Lucerne I hear a scraping /grinding noise that corresponds with the rotation of the wheel so the faster I go the faster the noise goes. The grinding stops when breaks are pressed. Braking perfromance appears to be perfectly fine. So thinking maybe it could be the plate on the back of the rotor rubbing against something I inspected it and made it wasn't making contact. I started to spin the rotor freely to listen for grinding noise and it was still there. It would grind when rotor hit a certain point in it's revolution seeming to be the same spot every time it was spun. This made me think about what could be wrong here. It is not the wear indicators because the pads are brand new and would not be able to even reach the rotor surface due to all the material still on the pad. It almost seems like the pads are catching on the rotor as it spins. Did I buy a brand new warped rotor? I bought the parts at AutoZone and I believe they are their duralast brand.
2 Answers
Brake disks should be machined pretty much true with virtually zero run-out. Sometimes however they're not perfectly machined and they'll have a very slight bit of run-out in them. This is whats causing the rubbing noise as the disks and pads contact each other untill they wear 'bed-in' together.
If this noise is only a very light contact rub between the pads and disk and there is NO pedal judder when braking, then it's probably ok and will lessen as the pads 'bed-in'. Try going on a short run for say 5 to 10 miles, braking lightly every so often when its safe, just to allow the brake pads 'bed-in', then see if the noise is still there. If not all well and good.
To check further.. jack each front wheel up a little (SAFELY, using axle stands etc) Try to rotate the disk/wheel by hand. If the disk run-out is excessive and it's causing the disk/wheel to bind at all, then the run-out is likely excessive and the disks need replacing under warranty. The same goes for any judder/vibration from the brakes that can be felt through the pedal when braking.
i'm an automotive machinist...there have been many new rotors and drums iv'e had to turn that were new but warped...so you can probably return them in which case they will probably also be warped as most new one seem to be or take them to a reputable machine shop and have them turned to true them up
