About a month ago, I started to get a shaking in this vehicle while under braking. While driving, the car is OK, and the steering wheel doesn't shake while braking, we feel it more in the pedal (no, not ABS feel). Without having taken the wheels off, I assumed it was front rotors (have owned the car for 5 years and never done brake work on it, figured it was time...) so got those and replaced them along with the pads and while the problem seems a little better, we still feel it. I haven't taken the wheels off the back yet but looking through the spokes, the pads look like they have decent material left and I don't see any abnormal scoring on the discs (though there's some non-uniform rust).
Again, we mostly feel it in the pedal, a kind of thumpa-thummpa-thumpa, and neither my wife nor I can come to a conclusion as to whether we feel it coming from the front or the back, though we both initially felt it was the front before those discs were replaced.
Since I'm not sure my visual inspection will be sufficient, are there any other causes for something like this (wheel bearings, worn suspension) or should I just go ahead and replace the rear discs and pads?