Tire Pressure Calculator
The fastest pressure is not the highest one. This calculator finds the point above which the tire stops absorbing bumps and starts passing them on to the bike and to you — and from there, rolling resistance rises again.
Recommended pressure
Front
Rear
Better slightly under than over
How rolling resistance rises as you move away from the recommendation, rear tire. Below it, the extra loss is in the tire; above it, in the vibration of bike and body. The shape of the curve is shown, not exact values.
How it is calculated. The base pressure comes from contact-patch geometry: it rises with wheel load and falls with tire width to the power of 1.5 and with the square root of wheel radius. It is then adjusted for surface roughness, tire casing and speed. The inner tube does not change the optimal pressure, but a butyl tube at low pressure risks pinch flats, so the calculator warns you. If you enter the nominal width, the real width is estimated from the rim internal width.
A starting point, not a rule. The number is an estimate, not a safety limit for your rim or tire. If it is higher than the manufacturer's rating, the rating applies. In mud, dust and on steep technical sections grip matters more than rolling resistance, so go lower there.
The approach is based on publicly published field measurements of rolling resistance (Tom Anhalt; SILCA).