Originally Posted by
Jim Kukula
That graph in Berto's article seems too rough. My formula, based on the 15% rule, some simple physics, and fitting to published tables:
P = 140 * L * W**(-1.5)
P is pressure, in psi
L is load on single wheel, in pounds
W is width, in mm
This formula was fit to the Schwalbe recommendation. Berto's charts are a bit lower. A reasonable fit to Berto would be:
P = 120 * L * W**(-1.5)