Force Calculation
Vertical Force
The vertical force can only be positive: in the case of a lift off condition of the tire from the ground, the resulting negative reaction force is set to 0. If a [DEFLECTION_LOAD_CURVE] block is present in tire property file then the data inside the block is used to calculate the vertical force. In this case the VERTICAL_STIFFNESS value is ignored.
Longitudinal Force
The calculation of the longitudinal force (Fx) depends on the longitudinal slip condition of the tire. Typically there are two distinct slip states: an elastic deformation state (where the longitudinal slip is less that a critical slip value) and a pure sliding state (where the longitudinal slip exceed the critical slip value).The critical longitudinal slip is calculated below:
In case of pure elastic deformation 
In case of pure sliding 
Where:
Lateral Force
Similarly, to the critical slip for longitudinal force, a critical lateral slip factor is calculated. It determines the boundary between pure elastic deformation conditions and pure sliding condition of the tire.
In case of elastic deformation state 
Where:
In case of sliding 
Rolling Resistance Moment
In the FIALA tire model the rolling resistance moment is purely a function of the normal force Fz:
Where omega is angular velocity of tire about spin axis.
Aligning Torque
The same critical lateral slip used in the Fy calculation is also used in determining the condition of the tire.In case
of elastic deformation state 
In case of sliding 
