Patent ID: 8032344

Claim:
A method of setting a parameter in a method of detecting a decreased tire air pressure for detecting a decreased tire air pressure based on a wheel rotational speed obtained from tires attached to a four-wheel driving vehicle, comprising: a vehicle model preparation step of preparing a vehicle model including a suspension member; a tire model preparation step of preparing a tire model; a step of inputting a friction coefficient between a tire and a road surface; and a simulation step of performing a running simulation of the vehicle model attached with the tire model, wherein a determination parameter for determining whether the tire has a decreased air pressure or not is set based on wheel rotational speeds of the tires of the respective four wheels obtained in the simulation step, the wheel rotation speed is obtained in consideration of at least the slip between the tire and a road surface and a change of a tire radius by an application of a load, the simulation step further calculates, based on the wheel rotational speed, a parameter for determining the use of different tires for determining that tires having different characteristics are attached to the vehicle, and the accuracy of the parameter for determining the use of different tires is checked by simulating the running of the vehicle on a climbing course and the running of the vehicle while pulling a trailer.