315/30R21 tire size
A 315/30R21 tire is 28.44 inches (722.4 mm) tall, 12.40 in (315 mm) wide and fits a 21-inch wheel. In inch notation it is roughly a 28.4x12.4R21 — a "28-inch" tire.
| Overall diameter | 28.44 in | 722.4 mm |
|---|---|---|
| Section width | 12.40 in | 315 mm |
| Sidewall height | 3.72 in | 94.5 mm |
| Circumference | 89.35 in | 2,269 mm |
| Revolutions | 709.1 per mile | 440.6 per km |
| Rim diameter | 21 in | 533.4 mm |
Compare 315/30R21 with another size
Alternative sizes on the same 21-inch wheel
Sizes in use within ±3 % of the overall diameter of 315/30R21:
Plus and minus sizes for 315/30R21
| Size | Wheel | Diameter | Difference |
|---|---|---|---|
| 345/35R19 | Minus 2 (19 in) | 28.51 in | +0.24% |
| 295/40R19 | Minus 2 (19 in) | 28.29 in | −0.53% |
| 285/40R19 | Minus 2 (19 in) | 27.98 in | −1.63% |
| 285/45R19 | Minus 2 (19 in) | 29.10 in | +2.31% |
| 305/35R20 | Minus 1 (20 in) | 28.41 in | −0.12% |
| 315/35R20 | Minus 1 (20 in) | 28.68 in | +0.84% |
| 345/30R20 | Minus 1 (20 in) | 28.15 in | −1.02% |
| 295/35R20 | Minus 1 (20 in) | 28.13 in | −1.09% |
| 285/30R22 | Plus 1 (22 in) | 28.73 in | +1.02% |
| 295/30R22 | Plus 1 (22 in) | 28.97 in | +1.85% |
| 355/25R22 | Plus 1 (22 in) | 28.99 in | +1.92% |
| 305/30R22 | Plus 1 (22 in) | 29.20 in | +2.69% |
Vehicles approved with 315/30R21 tires
Models whose Swiss type approval lists 315/30R21 as a standard or optional size (240 approvals in total). Always check your own vehicle's placard or papers.
Source: Swiss Federal Roads Office (FEDRO/ASTRA), open government data. Original data (downloaded 2026-09-29). Data processed by us; errors in processing are ours, not the publisher's.
Nearby 21-inch sizes
Reading the 315/30R21 size
- 315 — section width in millimetres (12.40 in).
- 30 — aspect ratio: the sidewall is 30 % of the width, 94.5 mm.
- R — radial construction (ZR on the sidewall means a high-speed rated radial; the dimensions are the same).
- 21 — fits a 21-inch diameter wheel.
The load index and speed rating (for example 91V) follow the size on the sidewall. They must meet at least the values on your vehicle's tire placard.