Hot tire pressure

As a tire heats up, the air inside expands and pressure rises, often by several psi over a session. What the tire actually does on track depends on its hot pressure, not the number you set in the paddock first thing in the morning. That is why serious drivers check pressures immediately after coming off track, before the tires cool.

Too high and the tread crowns slightly, the contact patch shrinks and the car feels skatey and slides earlier. Too low and the sidewalls flex too much, the car feels vague and the tire can overheat or roll onto its shoulder. Tire makers often publish a hot pressure target for track use; start there.

Set cold pressures based on what you saw hot last time. Adjust for weather: a hot afternoon may need lower starting pressures than a cool morning. Always measure with the same gauge, and never let air out of hot tires to hit a cold target, or you will be low next time out.