But all rings get 'squeezed'.... why does the contact radius get out of round once it gets squeezed a bit more than normal? If you were just pushing or pulling on the ring ends, like with a ring expander, then I agree; in that case, the bending force along the length of the ring will be uneven and will peak at a position opposite to the gap. But that is not what is going once in a cylinder. The ring is being pressed evenly inward all around, so I can't see what force would put it out of round. It is like a circular piece of spring steel with the forces being evenly distributed so I can't see anything that will put the circle out of round. And all rings have a gap so any end effects on radius and pressure would not change much... I would think. Honestly, not being obstinate, but the 'distorted contact radius' idea still does not make sense to me.