I started getting a vibration in my car when it hit 50 to 60mph. I would last a few miles than go away. I got new tires, had car aligned, and had the tires balanced twice. I just noticed the other day my back right rotor was very very hot compared to the other three. I jacked up the car and notice the wheel was difficult to turn compared to the rest and the brake pads had uneven wear. It would still turn but with more resistance than normal. I just replaced the caliper and rotors on both sides and the vibration is gone. Hope my gas milage increases now

 

I would say you had a frozen caliper. Thanks for sharing.