275/55 R21 tires diameter is 32.9 inches, section width is 10.8 inches and rim diameter is 21 inches.
|275||The first number shows that the tire has a width of 275 millimeters or approximately 10.8 inches.|
|55||The second number is the aspect ratio. In this case, it is 55%. It shows the height of the tire from the ground to rim edge, which is 55% of the width or ~ 152mm|
|R21||The letter R means this tire is radial. Most of all tires nowadays are radial. The number is the tire diameter in inches. It means that tire will fit 21 inch wheels|