315/55R21 tire size in inches
A 315/55R21 tire measures
34.6" tall × 12.4" wide
6.82" sidewall on a 21" wheel. 582 revolutions per mile.
315/55R21 means a tire 315 mm wide, with sidewalls 55% as tall as the tire is wide (173 mm), radial construction (R), for a 21 inch wheel.
315/55R21 specs
| Overall diameter (height) | 34.64 inches (880 mm) |
|---|---|
| Section width | 12.40 inches (315 mm) |
| Sidewall height | 6.82 inches (173 mm) |
| Wheel (rim) diameter | 21 inches |
| Circumference | 108.8 inches (2,764 mm) |
| Revolutions per mile | 582 |
| Revolutions per kilometer | 362 |
| Approximate rim width | 9.0" to 10.5" |
| In inches (flotation style) | 34.6x12.4R21 |
| Aspect ratio | 55% |
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 315/55R21 on a 21" wheel
These 21" sizes are within 3% of 315/55R21's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 345/50R21 | 34.58" | 13.58" | −0.2% | 59.9 mph | Compare |
| 355/50R21 | 34.98" | 13.98" | +1.0% | 60.6 mph | Compare |
| 325/55R21 | 35.07" | 12.80" | +1.3% | 60.8 mph | Compare |
| 305/55R21 | 34.21" | 12.01" | −1.3% | 59.2 mph | Compare |
| 335/50R21 | 34.19" | 13.19" | −1.3% | 59.2 mph | Compare |
| 325/50R21 | 33.80" | 12.80" | −2.4% | 58.5 mph | Compare |
| 335/55R21 | 35.51" | 13.19" | +2.5% | 61.5 mph | Compare |
| 295/55R21 | 33.78" | 11.61" | −2.5% | 58.5 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 325/65R18 | 18" | 34.63" | 0.0% | Compare |
| 305/65R19 | 19" | 34.61" | −0.1% | Compare |
| 285/65R20 | 20" | 34.59" | −0.2% | Compare |
| 295/80R16 | 16" | 34.58" | −0.2% | Compare |
| 355/45R22 | 22" | 34.58" | −0.2% | Compare |
| 335/40R24 | 24" | 34.55" | −0.3% | Compare |
| 295/55R22 | 22" | 34.78" | +0.4% | Compare |
| 335/55R20 | 20" | 34.51" | −0.4% | Compare |
| 325/50R22 | 22" | 34.80" | +0.4% | Compare |
| 305/70R18 | 18" | 34.81" | +0.5% | Compare |
| 335/60R19 | 19" | 34.83" | +0.5% | Compare |
| 285/75R18 | 18" | 34.83" | +0.5% | Compare |
One size up or down
Compare 315/55R21 with another size
Questions
- How tall is a 315/55R21 tire?
- A 315/55R21 tire is 34.6 inches tall (880 mm), calculated from the size. It is 12.4 inches wide with 6.8 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 315/55R21 mean?
- 315/55R21 means a tire 315 mm wide, with sidewalls 55% as tall as the tire is wide (173 mm), radial construction (R), for a 21 inch wheel.
- How many revolutions per mile does a 315/55R21 tire make?
- About 582 revolutions per mile, based on a circumference of 108.8 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 315/55R21 tire?
- Roughly 9.0" to 10.5". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 345/50R21 instead of 315/55R21?
- 345/50R21 is −0.06 inches (−0.2%) 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.