he Section Width (Tire Width) is the tire's width in millimeters from the widest point of its outer sidewall to the widest point of its inner sidewall when mounted. Using a 225/50ZR16 tire size as an example, the 225 is the tire's Section 225mm Width. The 225mm can be converted to inches by dividing it by 25.4 (the number of millimeters per inch). Example: 225mm / 25.4 = 8.86" - You may also simply specify in inches.
The Aspect Ratio (Sidewall Height/Profile) is the tire's sidewall height from rim to tread. Using a 225/50ZR16 tire size as an example, the 50 indicates that this tire's sidewall height is 50% of its section width. Since the tire's section width is 225mm and its section height is 50% of 225mm. By converting the 225mm to inches (225 / 25.4 = 8.86") and multiplying it by 50% (.50), the tire section is 4.43". If Aspect Ratio does not apply to the tire type you want, write in "Not Applicable", then list your Tire Height below.
If you do not know the Aspect Ratio of the tires you want, you may specify the tire's overall height.
The Rim Diameter is tire and wheel diameter expressed in inches. Using a 225/50ZR16 tire size as an example, the 16 is a 16" Rim Diameter.