This Tire SideWall Chart depicts the vertical area on the side of the tire between the tread edge and the tire bead. Convert the tire width of 215 mm to inches to get the sidewall height (8.46). Then multiply this by 65%. (. 65). This gives you the answer 5.5, which is the sidewall height in inches. The last four numbers on the Tire SideWall Chart represent the manufacturer's date. The initial two numbers represent the week, while the last two represent the year. (A tire with the number 2910, for example, was manufactured in the 29th week of 2010.) The thickness of the tire sidewalls varies from the shoulder to the bead area.