Truck's got 25k miles, so what I'm about to mention will be under warranty. But, I like to have some knowledge and be a step ahead of the dealership mechanics before I get there.
About two weeks ago, I noticed a thin metallic sound from the front end while going around long right-hand curves, like the circular on ramp to a highway. Couldn't determine if it changed with speed because by the time I got around to the on-lane, the wheels were straightened and the noise was gone. Took the truck to my independent mechanic for oil/filter last week. While on the lift, we spun the wheels and notice the noise coming from a thin metal plate on the inside of the rotor. At a certain wheel angle, the plate rubs the inside of the rotor slightly. Since it's a warranty issue (most likely), the conversation didn't get past "this is the problem - not a life or death thing".
What's the purpose of these plates? And, since they turn as part of the entire wheel assembly, why don't they make noise ALL the time?