What is Aspect Ratio?

A tire's aspect ratio determines the height of the sidewall, which ultimately determines the overall diameter of the tire. The aspect ratio is a percentage of the section width. So if you have a 70-series tire, that means the sidewall height is 70 percent of the tire's overall width. Aspect ratio for most bias ply tires is somewhere around 80 or 90 percent. Numeric sized tires (such as 6.00-16 or 6.70-15) that end in zero feature a 90-series aspect ratio, while numeric sizes that end in five (such as 6.95-14) feature an 80-series aspect ratio. Alpha numeric sizes (such as F70-15 or G78-14) have the aspect ratio clearly stated in the size.