315/25 R21 tires diameter is 27.2 inches, section width is 12.4 inches and rim diameter is 21 inches.
For each tire size there often there are several wheel sizes. You can't put very wide tires on narrow rims or vise versa. Here is what size of the rims do you need for 315/25 R21 tires:
Rim diameter x rim width
|315||The first number shows that the tire has a width of 315 millimeters or approximately 12.4 inches.|
|25||The second number is the aspect ratio. In this case, it is 25%. It shows the height of the tire from the ground to rim edge, which is 25% of the width or ~ 79mm|
|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|