bar
°C
°CAround 60–80 °C is typical after a hard road ride; track tyres run hotter.
kPa
Result
Pressure at the new temperature (gauge)2.411 bar
How it is calculated, with your numbers
- Pressure at the new temperature (gauge)
p2 = (p1 + atm / 100) × (t2 + 273.15) / (t1 + 273.15) − atm / 100(2 + 101.325 / 100) × (60 + 273.15) / (20 + 273.15) − 101.325 / 100 = 2.411 bar
Working uses the metric units the formula is written in.
- p1 Pressure set (gauge) (bar)
- t1 Tyre temperature when set (°C)
- t2 New tyre temperature (°C)
- atm Atmospheric pressure (kPa)
- p2 Pressure at the new temperature (gauge)
What it means
The air inside a tyre follows the gas law: at a fixed volume, absolute pressure is proportional to absolute temperature. A gauge reads pressure above atmospheric, so the calculator adds atmospheric pressure, scales by the temperature ratio in kelvin, and takes it off again.
That is why tyre makers specify cold pressures, and why track-day pressures are given hot or cold explicitly.
Assumptions and limits
- Tyre volume stays constant; in reality it grows very slightly when hot, so real rises are a little smaller.
Sources
- Ideal gas law (Gay-Lussac's law) at constant volume.