Tyre pressure

How this is calculated

Pressure rises with the load on the wheel and falls with tyre width. The model follows the "15 percent tyre drop" idea of Frank Berto, as published by Jan Heine of Rene Herse: for 100 kg split 45 to 55 it gives 125 and 155 psi on a 20 mm tyre and 45 and 53 psi on a 37 mm tyre.

On top of that: the front carries 47 percent of the load on the road and 46 percent on gravel. Tubeless runs as is, a tube needs 8 percent more, a tubular 5 percent less. Rough asphalt takes 7 percent off, hardpack gravel 14, mixed gravel 22, rough and loose gravel 30. Wet takes off another 5 percent. A wide rim makes the tyre measure wider, which lowers the pressure a little.

We checked the model against published examples, for instance 28 mm tubeless at 84 kg (about 65 and 70 psi) and 38 mm gravel at 95 kg (about 32 and 36 psi). It lands within a few percent. The range shown is plus and minus 7 percent, because the right pressure also depends on the tyre casing, your style and your taste.

Hookless rims are capped at 5.0 bar. Always keep to the maximum pressure printed on your tyre and rim. Start here, then change by 0.1 to 0.2 bar until the bike feels right.