181Best 315/45 R21 tires
2 rated tires available in this size, scored on dry, wet, snow, comfort and wear. Top overall right now is the Continental PremiumContact 6 at 81/100.
32.2″
overall diameter
12.4″
section width
21″
rim diameter
627.1
revs per mile
Best 315/45 R21 summer tires
1181Best 315/45 R21 winter tires
1
181Conversion
315/45 R21 in inches
| Overall diameter | 32.2″ |
| Section width | 12.4″ |
| Rim diameter | 21″ |
| Sidewall height | 142 mm |
| Circumference | 101″ |
| Revolutions per mile | 627.1 |
Wheels
What rims fit 315/45 R21 tires?
A tire fits a range of rim widths. Too narrow or too wide and the sidewall changes shape.
Minimum
8.5″
Ideal
10″
Maximum
11″
Rim diameter is fixed at 21″ — only the width varies. Estimated from the 12.4″ section width (70–90% rule).
Fitted from the factory on rims: 21x11.5.
Popular comparisons
Sizes often compared with 315/45 R21
Close alternatives — each opens in the tire size calculator.
Sidewall
315/45 R21 — what does it mean?
| Parameter | Meaning |
|---|---|
| 315 | The first number is the section width — 315 mm, or about 12.4 inches across the widest part of the tire. |
| 45 | The second number is the aspect ratio: sidewall height as a percentage of width. At 45%, the sidewall is about 142 mm tall. |
| R21 | R means radial construction, which nearly all modern tires use. The number is the rim diameter in inches — this tire fits a 21-inch wheel. |