A few months ago I was driving home with my 2 1/2 year old son in his car seat when I heard a terrifying sound coming from the rear brake area. I was on I-75 going 65 when a grinding sound and then the sound of something large rattling around. Figuring I lost a rear brake pad (it happened once before on my other Volvo) and that I was almost home, I kept going. I drove it slowly home. At slower speeds, it sounded like something was grinding, but when I sped up it went away. As long as I kept moving it seemed fine. When I got home, let my wife take my son inside, I pulled the left rear wheel off. There it was....a HUGE ROCK !! So large that it was wedged between the caliper and the wheel. I brought my son outside to see what I was doing. He looked at me and said "Daddy, I gave you rock!" Yes, he stuffed it through the slot in the wheel which was a perfect fit. Smart kid, bad kid, I don't know. I did have to replace the rear pads though. One pad had literly literally broken off the metal portion and fell off. All is well now.
Ben