I've recently noticed that my car has been experiencing a low vibration accompanied by a grinding/growling noise at low speeds (between 3 and 10mph). It sounds/feels like it's coming from the rear of the car rather than the front. The only suspension mods I have are H&R springs and Tokico shocks. I have Foose wheels installed that I drove on for a while before I realized I needed hubcentric rings (they were causing vibrations at high speeds). It's been a little while since I've had the tires balanced. That's all the pertinent information I can really think of right now. Any help?