This noise starts to happen in wet weather. It goes away again when the brakes dry out. I can’t observe any correlation with the make/model/year of the car, the age of the car, or the condition of the brakes. I have noticed it over the years on a wide variety of makes and models, domestic and foreign. Old beaters and brand new cars off the showroom floor. Once when I heard brakes making this grinding I took the car into a shop to get the brakes looked at. They told me there was nothing wrong with the brakes.
What’s the Straight Dope on this wet-weather brake noise?