TIRE GROUNDED STATE ESTIMATION METHOD

A tire contact state estimation method includes: an information acquisition step of acquiring information of the tire; a correlation strength calculation step of calculating a first correlation strength between the rotational velocity and the braking and driving force, and also calculating a second correlation strength between the slip angle and the generated lateral force; a change detection step of detecting whether the first correlation strength has increased or decreased by a first threshold or more with respect to a predetermined first reference value, and also detecting whether the second correlation strength has increased or decreased by a second threshold or more with respect to a predetermined second reference value; and an estimation step of estimating at least two of the following: a condition of a road surface in contact with the tire, a tire internal pressure state, and a tire abrasion state.