Originally Posted by operator
A tire mounted correctly should have no noticeable hop in it.
+1
There is no good reason for an out-of-round tire but it does happen. From my experiences tires with a noticeable hump are a sign of a manufacturing defect, damage to the casing, improper mounting, or often a sign that a small part of the tube is caught between the rim and the tire. With high pressure road tires if any part of the tube is between the tire and any part of the rim not only will you notice a hump, but you are about to experience SARD - Simultaneous Automatic Rapid Deflation.
Al