Hi Dave, You are quiet right about the benefit of going back over the basics as they are often forgotten(or not quiet learn't in the first place). Some years ago I had the pleasure of being invited to Lochead's head quarters to become part of a three day "Think tank" on how to educate the motor trade on braking problems that where costing the company money(high spend customers returning parts for the wrong reason). The problem you talk of is known as "Thick Thin Syndrome" and is indeed caused by the pad rubbing the disc when the brake is not applied,(high points only) this is why it takes a few 100/1000 miles to show its self and can be proved with a micrometer. One other problem they had was getting people to "Bleed" the system BEFORE replacing components and not only after(the number one reason for wheel cylinder returns). Every day is a school day in this trade. Regards Mark. P.S. I love your piston seal animation