I was told by inflating them to a higher pressure they stretch or grow in size and then displace more water. The greater Buoyancy then makes the tires sit higher giving you more speed in the water. Given that they say 20 PSI max inflation on the sidewall I was even thinking of taking them to that if what I understand is true. Maybe someone can chime in who has experimented with this. Right now the tires tape just a tad over 26 inches across with 12 PSI.