Tire contact state estimation method

A tire contact state estimation method of estimating information on a contact state of a tire mounted on a vehicle to a road surface, the tire contact state estimation method comprising:

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