Originally Posted by
gsa103
You can find tons of graphs of tire psi vs rolling resistance. You might reduce the rolling resistance by ~5%, at the expense of significantly worse handling.
And even that's highly dependent on the surface. The rougher the surface, the less an increase in pressure is going to reduce rolling resistance. Raising pressure can even increase rolling resistance because the tire has to bounce over things instead of being able to just roll over them - and bouncing redirects motion and absorbs energy.
Why would a large tire at high pressure literally blow a rim apart? Let's see: 2" tire at 100 psi. Assume a 1" radius for the inflated tube cross section, and a 13" radius for the tube itself. Surface area of a torus is:
4 x pi^2 x R x r
4 x 3.14^2 x 13 x 1 = 513 square inches
At 100 psi, the outward pressure on the tube totals over 51,000 pounds.