dingster

My car is making a grinding sound(best described as a groan) from the front brakes. It almost sounds like the squeeking sound bicycle brakes make but the pitch is lower. It's rythmical and proportional to wheel rpm. At higher speed it disappears.

I jacked up the front of the car and spun the wheels by hand and I can hear the pads making contact with the rotor but there's a small section on both rotors where the sound goes away. This indicates the rotors are not 100% true but it's not so bad since I can't feel it in the pedals.

I think the noise has to do with the fact I didn't put any anti-squeal pads in the back of the front pads. Does anyone think by adding anti squeal pads will get rid of this noise? Where can I get them and how do I push the pistons back on a 4piston caliper?(C-clamps?). Do you think my rotors are warped or this slight warpage is OK?

TIA