When it rains, my brakes grind for several stops and then clear up. What is causing this?
The brake pads have metal in them, and the rotors are made of metal, and when it rains they get wet and surface rust will immediately start to rust the rotors. As soon as you start to drive off, the noise is the rusted rotors and metal pads grinding off the rust. This is normal for most vehicles.
I have a Matrix myself and it does it every time it rains. I replaced my brakes recently and now it does not do it as bad, but still does it. The problem may be the rotor and pad quality since this brake job, I put really good quality pads and rotors on.