I am going to guess at an amount but the pads should only release about a 1/16th or so on each side. There will not be a ton of movement there with new pads. the springs only help keep the piston expanded as the wear gets greater. I am working off knowledge of my manual brakes but the concept is the same i believe.

Is is possible that the rotor is wrong, if off by a few hundreds of an inch on thickness to big?