315/30R21 tire size in inches
A 315/30R21 tire measures
28.4" tall × 12.4" wide
3.72" sidewall on a 21" wheel. 709 revolutions per mile.
315/30R21 means a tire 315 mm wide, with sidewalls 30% as tall as the tire is wide (95 mm), radial construction (R), for a 21 inch wheel.
315/30R21 specs
| Overall diameter (height) | 28.44 inches (722 mm) |
|---|---|
| Section width | 12.40 inches (315 mm) |
| Sidewall height | 3.72 inches (95 mm) |
| Wheel (rim) diameter | 21 inches |
| Circumference | 89.3 inches (2,269 mm) |
| Revolutions per mile | 709 |
| Revolutions per kilometer | 441 |
| Approximate rim width | 10.5" to 12.0" |
| In inches (flotation style) | 28.4x12.4R21 |
| Aspect ratio | 30% |
Calculated from the size. Real tires differ by brand, model and tread depth, typically by a few tenths of an inch.
Sizes that can replace 315/30R21 on a 21" wheel
These 21" sizes are within 3% of 315/30R21's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 235/40R21 | 28.40" | 9.25" | −0.1% | 59.9 mph | Compare |
| 265/35R21 | 28.30" | 10.43" | −0.5% | 59.7 mph | Compare |
| 275/35R21 | 28.58" | 10.83" | +0.5% | 60.3 mph | Compare |
| 305/30R21 | 28.20" | 12.01" | −0.8% | 59.5 mph | Compare |
| 325/30R21 | 28.68" | 12.80" | +0.8% | 60.5 mph | Compare |
| 245/40R21 | 28.72" | 9.65" | +1.0% | 60.6 mph | Compare |
| 225/40R21 | 28.09" | 8.86" | −1.2% | 59.3 mph | Compare |
| 255/35R21 | 28.03" | 10.04" | −1.5% | 59.1 mph | Compare |
| 285/35R21 | 28.85" | 11.22" | +1.5% | 60.9 mph | Compare |
| 355/25R21 | 27.99" | 13.98" | −1.6% | 59.0 mph | Compare |
| 295/30R21 | 27.97" | 11.61" | −1.7% | 59.0 mph | Compare |
| 335/30R21 | 28.91" | 13.19" | +1.7% | 61.0 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 245/80R13 | 13" | 28.43" | 0.0% | Compare |
| 265/50R18 | 18" | 28.43" | 0.0% | Compare |
| 295/45R18 | 18" | 28.45" | 0.0% | Compare |
| 215/50R20 | 20" | 28.46" | +0.1% | Compare |
| 285/60R15 | 15" | 28.46" | +0.1% | Compare |
| 245/75R14 | 14" | 28.47" | +0.1% | Compare |
| 235/35R22 | 22" | 28.48" | +0.1% | Compare |
| 265/55R17 | 17" | 28.48" | +0.1% | Compare |
| 305/35R20 | 20" | 28.41" | −0.1% | Compare |
| 225/70R16 | 16" | 28.40" | −0.1% | Compare |
| 325/25R22 | 22" | 28.40" | −0.2% | Compare |
| 215/85R14 | 14" | 28.39" | −0.2% | Compare |
One size up or down
- 305/30R21narrower: 28.2" × 12.0"
- 325/30R21wider: 28.7" × 12.8"
- 315/25R21lower profile: 27.2" × 12.4"
- 315/35R21taller sidewall: 29.7" × 12.4"
Compare 315/30R21 with another size
Questions
- How tall is a 315/30R21 tire?
- A 315/30R21 tire is 28.4 inches tall (722 mm), calculated from the size. It is 12.4 inches wide with 3.7 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 315/30R21 mean?
- 315/30R21 means a tire 315 mm wide, with sidewalls 30% as tall as the tire is wide (95 mm), radial construction (R), for a 21 inch wheel.
- How many revolutions per mile does a 315/30R21 tire make?
- About 709 revolutions per mile, based on a circumference of 89.3 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 315/30R21 tire?
- Roughly 10.5" to 12.0". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 235/40R21 instead of 315/30R21?
- 235/40R21 is −0.04 inches (−0.1%) in overall diameter, so at an indicated 60 mph you would be doing 59.9 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.