305/40R20 tire size in inches
A 305/40R20 tire measures
29.6" tall × 12.0" wide
4.80" sidewall on a 20" wheel. 681 revolutions per mile.
305/40R20 means a tire 305 mm wide, with sidewalls 40% as tall as the tire is wide (122 mm), radial construction (R), for a 20 inch wheel.
305/40R20 specs
| Overall diameter (height) | 29.61 inches (752 mm) |
|---|---|
| Section width | 12.01 inches (305 mm) |
| Sidewall height | 4.80 inches (122 mm) |
| Wheel (rim) diameter | 20 inches |
| Circumference | 93.0 inches (2,362 mm) |
| Revolutions per mile | 681 |
| Revolutions per kilometer | 423 |
| Approximate rim width | 10.0" to 11.5" |
| In inches (flotation style) | 29.6x12.0R20 |
| 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 305/40R20 on a 20" wheel
These 20" sizes are within 3% of 305/40R20's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 245/50R20 | 29.65" | 9.65" | +0.1% | 60.1 mph | Compare |
| 345/35R20 | 29.51" | 13.58" | −0.3% | 59.8 mph | Compare |
| 225/55R20 | 29.74" | 8.86" | +0.5% | 60.3 mph | Compare |
| 275/45R20 | 29.74" | 10.83" | +0.5% | 60.3 mph | Compare |
| 355/35R20 | 29.78" | 13.98" | +0.6% | 60.4 mph | Compare |
| 265/45R20 | 29.39" | 10.43" | −0.7% | 59.6 mph | Compare |
| 215/55R20 | 29.31" | 8.46" | −1.0% | 59.4 mph | Compare |
| 295/40R20 | 29.29" | 11.61" | −1.1% | 59.4 mph | Compare |
| 315/40R20 | 29.92" | 12.40" | +1.1% | 60.6 mph | Compare |
| 235/50R20 | 29.25" | 9.25" | −1.2% | 59.3 mph | Compare |
| 335/35R20 | 29.23" | 13.19" | −1.3% | 59.2 mph | Compare |
| 255/50R20 | 30.04" | 10.04" | +1.5% | 60.9 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 265/70R15 | 15" | 29.61" | 0.0% | Compare |
| 245/55R19 | 19" | 29.61" | 0.0% | Compare |
| 285/25R24 | 24" | 29.61" | 0.0% | Compare |
| 295/50R18 | 18" | 29.61" | 0.0% | Compare |
| 285/65R15 | 15" | 29.59" | −0.1% | Compare |
| 225/60R19 | 19" | 29.63" | +0.1% | Compare |
| 275/35R22 | 22" | 29.58" | −0.1% | Compare |
| 245/60R18 | 18" | 29.57" | −0.1% | Compare |
| 265/75R14 | 14" | 29.65" | +0.1% | Compare |
| 265/65R16 | 16" | 29.56" | −0.1% | Compare |
| 275/40R21 | 21" | 29.66" | +0.2% | Compare |
| 335/40R19 | 19" | 29.55" | −0.2% | Compare |
One size up or down
- 295/40R20narrower: 29.3" × 11.6"
- 315/40R20wider: 29.9" × 12.4"
- 305/35R20lower profile: 28.4" × 12.0"
- 305/45R20taller sidewall: 30.8" × 12.0"
Compare 305/40R20 with another size
Questions
- How tall is a 305/40R20 tire?
- A 305/40R20 tire is 29.6 inches tall (752 mm), calculated from the size. It is 12.0 inches wide with 4.8 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 305/40R20 mean?
- 305/40R20 means a tire 305 mm wide, with sidewalls 40% as tall as the tire is wide (122 mm), radial construction (R), for a 20 inch wheel.
- How many revolutions per mile does a 305/40R20 tire make?
- About 681 revolutions per mile, based on a circumference of 93.0 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 305/40R20 tire?
- Roughly 10.0" to 11.5". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 245/50R20 instead of 305/40R20?
- 245/50R20 is +0.04 inches (+0.1%) in overall diameter, so at an indicated 60 mph you would be doing 60.1 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.