Run this through everyone's think tank. Most radial tires have a steel belt
under the tread. That belt's circumference never changes. But the
rubber tread over the belt has a thickness of say 3/4 inch. If the steel belt
is bent over diameter, the rubber at the outside (contact patch) must
"stretch" in order to follow the belt. The smaller the diameter the steel belt
passes over the more "stretch" the rubber at the contact patch must
undergo for it to follow the belt.
Thus the difference between a tire at low pressure and one at high pressure has
more to do with how much the tread (contact patch) must stretch or
contract to follow the steel belt.
REgards,
Blake
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