I own a 2010 Dodge Charger SXT. I recently replaced my front and back brake pads and front rotors. The back rotors are in okay condition, a little texture on them but not much. On occasion I am not able to depress the brake pedal completely when I first engage the brakes. I usually quickly depresses after some vibration (in the pedal not the wheel) and some noice from the firewall area. It usually happens when I'm on an incline or decline. My fluid level is normal. All of this was occuring prior to the replacements mentioned earlier. Does anyone have any idea what is going on?