Tyre pressures determine the shape of the tyres. Too low, and the tyre will crush against the ground, increasing the surface area of the tyre in contact with the ground, temperature and wear.

## HOW TO DETERMINE THE IDEAL PRESSURE?

In theory, the ideal pressure is achieved when the inside, middle and outside of the tyre work equally well. How do you know this? Just look at their respective temperatures. If these parts work equally, they will have the same temperatures (the more it works, the hotter it gets).

But beware, because of the camber, the interior will inevitably be warmer. So we will try to have a linear temperature distribution: 76°/ 73°/ 70° (int, middle, out) is a good distribution, while 76°/75°/70° is not (the centre works too much, you have to lower the pressure).

The more the tyre isinflated, the less friction there is between the tyre and the ground. Friction is the phenomenon that transforms speed into heat, which is the principle of the disc brake.

It is also for this reason that increasing the pressure increases the top speed: less energy is dissipated through friction.

Tyre pressures can also be used to balance the level of grip between the front and rear of the car, as well as wear and tear.

Rule of thumb :

• Decreasing pressure increases temperature.
• Increasing the temperature (by other means: toe-in, aerodynamic load) increases the pressure (see explanation below).
• Lower pressures: more grip (up to a certain point), less reactive and more predictable car, more wear (because more friction).
• Higher pressures: less grip, more responsive and less predictable car, less wear, more top speed

## And with Profiler software ?

With Profiler, we can’t monitor the pressure, only the tire temperature.

## And what about the perfect temperature ?

Mainly to the feeling! Impossible to use telemetry to determine ideal values. Ideal temperatures depend on the constitution of the compound. This is generally a parameter that the manufacturer provides. If this is not the case, you will have to try different temperatures to determine which one works best. You can also rely on the ATH colour code: green tyres are normally at the right temperature.

## WHY INCREASING THE PRESSURE LOWERS THE TEMPERATURE?

Overall, two opposing phenomena govern the behaviour of a tyre:

• PV = nRT (ideal gas law). This equation says that in a volume (a bottle, a tyre), if the pressure increases, the temperature also increases, and vice versa (if the temperature increases, the pressure also increases). Based on this equation, increasing the pressure should increase the temperature of the tyres.
• Except that if the pressure is lowered, the tyre will deform more, so there will be more friction with the ground, therefore more heat created, therefore more temperature. This is the most important phenomenon.