Bob is right about the air. It's impossible for trapped air to cause the pulling in a closed pressure system (fluid dynamics). It would simply cause a spongy pedal feel. However, if the inner hose on one side is damaged (from "hanging" the calipers), it could cause a blockage or partial blockage which would definitley change the pressure from one side to the other.
Bob's checklist is correct and accurate (sticky calipers, bad pads, defective rotors, suspension geometry, tire variations). Most likely, it's sticky calipers.
Keith
