Outside of lap times, tire data is the most significant data you have available for determining a car's performance, and is the data by which most suspension adjustments are determined. Tire data consists of the tire temperatures, pressures, and appearance of the wear pattern. For all the emphasis you'll hear in the paddock about tire pressure, it is actually more important to collect tire temperature data than pressure data. Ultimately, all suspension adjustments including tire pressure are aimed at maximizing the tire contact patch, and temperature data is the most direct measurement we have to optimize that. To avoid getting focused in the wrong place, it is important to understand the role tire pressure plays.
Tire pressure is an adjustable element of the complete suspension system of the car.
Not so with tire pressure. It rises due to the friction generated between the rubber and the track surface. Tire pressure has to be estimated at the beginning of the session to account for this rise so that it ends up being what you want after about three laps. This estimating part is what people get confused about. All of these items must be balanced.