811Revs/Mile. 205/55R16. Diameter : 24.9" Width : 8.1" Wheel : 16" x " Sidewall : 4.4" Circum. : 78.1" Revs/Mile : 811. Upsizing Wheels or Tires? When searching for the
TireSize and Comparison Calculator calculate tire diameter from code and compare speedometer differences for tire sizes. The first number 225 is the tire width in millimeters. The 2nd number 55 is used to calculate the sidewall height or "aspect ratio", by percentage. So, the sidewall height of a 225/55 R 18 tire is 60% of 225 = 192. The205/60R16 tire has the following features: the first three digits 205 refer to the width of the tire in millimetres. The second two-digit number 60 refers to the ratio between the height of the sidewall and the width of the tire. R stands for “Radial” and the last two figures 16 indicate the wheel diameter in inches.