)
The longitudinal force depends on the:
•Vertical force ()
•Current coefficient of friction (
)
•Longitudinal slip ratio (
)
•Slip angle (
)
The comprehensive slip ratio (
):
(1)
The current value coefficient of friction (
):
(2)
A critical longitudinal slip (
)
(3)
1. Elastic Deformation State: 
(4)
: Partial derivative of
longitudinal force (
) with respect to
longitudinal slip ratio (
) at zero longitudinal
slip
2. Complete Sliding State: 
(5)
where,
