A vehicle and associated method for calculating tire saturation is provided. The method may include the stability control computer calculating slip ratio and longitudinal force for the tire, calculating tire longitudinal stiffness by dividing longitudinal force by slip ratio, calculating tire saturation from tire longitudinal stiffness, and the stability control computer altering dynamic control of the vehicle based on calculated tire saturation. The stability control computer may calculate tire saturation from a tire saturation membership function which includes a first tire longitudinal stiffness value representing an unsaturated tire, a second tire longitudinal stiffness value representing a saturated tire, and a function line connecting the first tire longitudinal stiffness value to the second tire longitudinal stiffness value.