Technical Papers to better understand many fundamental aspects of engine, chassis and tires in motorsport

TIRE FEATURES vs INFLATION PRESSURE

Tyre features in function of the inflation pressure - Technical Explanation

In the motorsport the tires features are today the starting point to begin the work, both in the vehicle development, both in the setup phase.

Tyre Features vs Inflation Pressure

In this paper we want put on focus how the tires pressure affects significantly these features, and therefore how much is important the choice of the tires pressure to have the best performance.

The tire pressure affects in fact on these fundmental aspects:

-	grip
-	cornering stiffness
-	rolling resistance
-	damping ground asperity

For each of these aspects the pressure affects in a different manner, therefore the choice of the pressure will have to be a comprimise to satisfy in the best way the different needs.

ADERENZA

Changing the inflation pressure, change the footprint, and the load part absorbed from the tire side. You’ll have therefore a different contact pressure, and then a different grip level. Usually with lower inflation pressure the contact area increases and you’ll have a higher grip level, but an excessive wear of the tread part near the sides of the tire. Increasing the inflation pressure decreases the grip level, but you’ll have a more homogeneous consumption between the center and lateral areas of the tread.

Tyre Grip in function of the Inflation Pressure

CORNERING STIFFNESS
The pressure affects on the lateral stiffness, and on the cornering stiffness of the tire, and usually if the pressure increases, also the stiffness increases. The pressure therefore can play an important role, both on the driving, both on the drag force for the slip angle.

ROLLING RESISTANCE

Changing the inflation pressure, changes the vertical stiffness of the tire, and therefore the deformation entity of the tire carcass during the rolling. For the features of the rubber, that is fundmental constituent of the carcass, the energy used for the deformation, it is not fully refunded (hysteresis), therefore there is an energy loss. Increasing the inflation pressure the deformation of the carcass when the tire is loaded is lower, then also the loss for rolling will be lower.

DAMPING GROUND ASPERITY
How you’ve seen for the rolling, the vertical stiffness of the tire changes with the pressure. With lower pressure you’ll have higher deformation, and then higher ease to absorb the ground asperity, facilitating the maintenance of the tire-asphalt contact.

From this brief description appears evident as decreasing the pressure will be favorites some aspects (grip and damping ground asperity), and as instead increasing the pressure will be favorites others (rolling and slip angle resistance).

VEHICLE TRIM

In addition to these aspects there is the difference between fron and rear slip angle that together the balance of the vehicle determines the basic vehicle trim (oversteer or understeer) that you can have, and therefore can be modified acting on the pressures front and rear that modifies the respectives cornering stiffness.

How do you find therefore the optimal pressures for the tyres?

It's fundmental to know the tyres features and then to make the choices more adapts in function, of the vehicle features, of the track features, and of the driving style of the driver.

USEFUL LINK

Software for the calculation of the kart tyres optimal pressures SET-UP TYRE

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