285/40R21 tire size in inches
A 285/40R21 tire measures
30.0" tall × 11.2" wide
4.49" sidewall on a 21" wheel. 673 revolutions per mile.
285/40R21 means a tire 285 mm wide, with sidewalls 40% as tall as the tire is wide (114 mm), radial construction (R), for a 21 inch wheel.
285/40R21 specs
| Overall diameter (height) | 29.98 inches (761 mm) |
|---|---|
| Section width | 11.22 inches (285 mm) |
| Sidewall height | 4.49 inches (114 mm) |
| Wheel (rim) diameter | 21 inches |
| Circumference | 94.2 inches (2,392 mm) |
| Revolutions per mile | 673 |
| Revolutions per kilometer | 418 |
| Approximate rim width | 9.5" to 11.0" |
| In inches (flotation style) | 30.0x11.2R21 |
| Aspect ratio | 40% |
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 285/40R21 on a 21" wheel
These 21" sizes are within 3% of 285/40R21's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 325/35R21 | 29.96" | 12.80" | −0.1% | 60.0 mph | Compare |
| 255/45R21 | 30.04" | 10.04" | +0.2% | 60.1 mph | Compare |
| 225/50R21 | 29.86" | 8.86" | −0.4% | 59.8 mph | Compare |
| 335/35R21 | 30.23" | 13.19" | +0.9% | 60.5 mph | Compare |
| 235/50R21 | 30.25" | 9.25" | +0.9% | 60.6 mph | Compare |
| 245/45R21 | 29.68" | 9.65" | −1.0% | 59.4 mph | Compare |
| 315/35R21 | 29.68" | 12.40" | −1.0% | 59.4 mph | Compare |
| 275/40R21 | 29.66" | 10.83" | −1.1% | 59.4 mph | Compare |
| 295/40R21 | 30.29" | 11.61" | +1.1% | 60.6 mph | Compare |
| 265/45R21 | 30.39" | 10.43" | +1.4% | 60.8 mph | Compare |
| 345/35R21 | 30.51" | 13.58" | +1.8% | 61.1 mph | Compare |
| 305/35R21 | 29.41" | 12.01" | −1.9% | 58.9 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 275/60R17 | 17" | 29.99" | +0.1% | Compare |
| 235/70R17 | 17" | 29.95" | −0.1% | Compare |
| 30x9.50R15 | 15" | 30.00" | +0.1% | Compare |
| 215/65R19 | 19" | 30.00" | +0.1% | Compare |
| 305/25R24 | 24" | 30.00" | +0.1% | Compare |
| 305/50R18 | 18" | 30.01" | +0.1% | Compare |
| 295/60R16 | 16" | 29.94" | −0.1% | Compare |
| 255/30R24 | 24" | 30.02" | +0.2% | Compare |
| 235/65R18 | 18" | 30.03" | +0.2% | Compare |
| 315/40R20 | 20" | 29.92" | −0.2% | Compare |
| 255/40R22 | 22" | 30.03" | +0.2% | Compare |
| 255/50R20 | 20" | 30.04" | +0.2% | Compare |
One size up or down
- 275/40R21narrower: 29.7" × 10.8"
- 295/40R21wider: 30.3" × 11.6"
- 285/35R21lower profile: 28.9" × 11.2"
- 285/45R21taller sidewall: 31.1" × 11.2"
Compare 285/40R21 with another size
Questions
- How tall is a 285/40R21 tire?
- A 285/40R21 tire is 30.0 inches tall (761 mm), calculated from the size. It is 11.2 inches wide with 4.5 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 285/40R21 mean?
- 285/40R21 means a tire 285 mm wide, with sidewalls 40% as tall as the tire is wide (114 mm), radial construction (R), for a 21 inch wheel.
- How many revolutions per mile does a 285/40R21 tire make?
- About 673 revolutions per mile, based on a circumference of 94.2 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 285/40R21 tire?
- Roughly 9.5" to 11.0". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 325/35R21 instead of 285/40R21?
- 325/35R21 is −0.02 inches (−0.1%) in overall diameter, so at an indicated 60 mph you would be doing 60.0 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.