What does 275-40R20 mean?
Tire sizes are easy to understand once you learn how to read them. On this page you'll find a color-coded explanation of the 275-40R20 tire code.
This number indicates that your tire has a width of 275 millimeters.
This number means that your tire has an aspect ratio of 40%. In other words, your tire's sidewall height (from the edge of the rim to the tire's tread) is 40% of the width. In this case, the sidewall height works out to be 110 millimeters.
This letter denotes how your tire was constructed. Radial is the standard construction method for about 99% of all tires sold today.
The tire size was designed to fit rims or wheels that are 20 inches in diameter.