Method and device for measuring wheel alignment of car

A method of measuring wheel alignment of an automobile, comprising the steps of:

• supporting an automobile body with a wheel mount vertically movably mounted thereon, and lifting the wheel mount to a predetermined vertical position which is set so as to be lower than the position that the wheel mount takes when the automobile is running;
• and
• measuring the position of the wheel mount which is lifted and a tilt angle in a predetermined direction of the wheel mount;
• wherein said step of measuring comprises the steps of:
• calculating the gradients of straight lines respectively interconnecting first reference coordinates and measured coordinates, said first reference coordinates comprising coordinates representative of the position of the wheel mount which is measured when the wheel mount starts being lifted and the tilt angle in the predetermined direction of the wheel mount which is measured in the measured position of the wheel mount, said measured coordinates comprising a plurality of coordinates representative of the positions of the wheel mount which are measured at predetermined intervals while the wheel mount is being lifted to said predetermined vertical position and the tilt angles in the predetermined direction of the wheel mount which are measured in the respective measured positions of the wheel mount;
• and
• calculating an estimated value of the tilt angle in the predetermined direction of the wheel mount at the position that the wheel mount takes when the automobile is running, based on the differences between the gradients of straight lines respectively interconnecting second reference coordinates, which have been calculated in advance, and set coordinates and the gradients of the straight lines respectively interconnecting said first reference coordinates and said measured coordinates, said second reference coordinates comprising coordinates representative of the position of the wheel mount at said first reference coordinates and a predetermined correct tilt angle in the predetermined direction of the wheel mount at said position of the wheel mount, said set coordinates comprising a plurality of coordinates representative of the respective positions of the wheel mount at said measured coordinates and predetermined correct tilt angles in the predetermined direction of the wheel mount at said positions of the wheel mount.