I've had new pads and rotors for a few months now and at first they were totally fine, but now the front brakes (not sure which side) are making a loud noise when I am braking at higher speeds. It usually occurs when I'm braking firmly from say like 50mph and higher. It's not a squeal it's more of a grinding noise but it has a deep tone too it. I am not really sure how to describe it. Brakes are working completely fine, pads look good, rotors look good too. It never makes this noise unless I am going at a higher speed and apply the brakes. Any thoughts?