What does a R with a number indicate on a tire's sidewall?

• A. Maximum load rating
• B. Tread depth
• C. Amount of retreads on the tire
• D. Tire width in millimeters

Answer: (C)

R with a number on a tire sidewall shows radial construction and the wheel diameter in inches. The letter R means the tire is built as radial ply, which is the standard construction for most passenger and light truck tires. The number that follows is the wheel diameter the tire is designed to fit, listed in inches. So in a common size like P225/60R16, the tire is radial and fits a 16-inch wheel.

This marking is not about how much weight the tire can carry, nor about how deep the tread is, nor about how many retreads the tire has, nor about the tire width. The width is actually indicated by the first number in the size code (the 225 in that example).