Brakes have plenty of life left in them, but after about 10 min of driving and I've had a chance to hit the brakes a few times, they start to make a grinding sound only in the front. This also only happens at low speeds. I've also have heard a few times when I'm coasting slowly, not applying the brakes at all, it sounds like the pads are rubbing against the rotors still (not making a grinding sound but I can hear contact). Maybe the piston needs a little silicone lube? Any thoughts?