I run my tires about 5-10 PSI below max tire pressure. Lately I have been using fatter tires and yes they do appear to be flattening out when viewed from above as when siting on the bicycle seat. But if viewed from the side they are not flat at all. Get someone to look closely at the tires when you are ridding to make sure.
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No matter where you're at... There you are... Δf:=f(1/2)-f(-1/2)