TIRE SIDEWALL ASPECT RATIO
Following the three digit Section Width is a two digit number indicating the aspect ratio of the tire.
This indicates the tire's sidewall height from rim to tread as a percentage of the section width. The higher the number the taller the tire sidewall. This tire width is 60 percent of the side wall height.
R - Typically following the sidewall aspect ratio is the letter "R" indicating that the internal construction of the tire is of a radial design.
Nearly all tires in highway use today are radial. Non radial tires are of "Bias ply" and are indicated by the absence of "R" coding. Bias Ply tires typically do not perform as well as radials. Many bias ply tires sold today are used on historically "correct" vehicles that are not in daily use.
Next Page: Speed Rating and Wheel Diameter
Before you replace the tires on your car, minivan or truck understand the tire information code.
You will avoid being sold more tire than you need, and more importantly can avoid buying less tire than you need, which can be dangerous.