I'm assuming "lower radius arm" means the control arm . . there's a bushing at the rear of this arm, was that replaced? That can cause the vibration.
Brake rotors can be distorted or "warped" as a result of overtorquing wheel lugs. Could this have happened when you had the tires replaced? Lastly, worn wheel bearing or distorted hubs can can transfer their problems to the rotors. It's important to take that into account when getting new rotors; good mechanics will check to see if they need to resurface them to alleviate these issues.