255/40R18 tire size in inches
A 255/40R18 tire measures
26.0" tall × 10.0" wide
4.02" sidewall on a 18" wheel. 775 revolutions per mile.
255/40R18 means a tire 255 mm wide, with sidewalls 40% as tall as the tire is wide (102 mm), radial construction (R), for a 18 inch wheel.
255/40R18 specs
| Overall diameter (height) | 26.03 inches (661 mm) |
|---|---|
| Section width | 10.04 inches (255 mm) |
| Sidewall height | 4.02 inches (102 mm) |
| Wheel (rim) diameter | 18 inches |
| Circumference | 81.8 inches (2,077 mm) |
| Revolutions per mile | 775 |
| Revolutions per kilometer | 481 |
| Approximate rim width | 8.5" to 10.0" |
| In inches (flotation style) | 26.0x10.0R18 |
| 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 255/40R18 on a 18" wheel
These 18" sizes are within 3% of 255/40R18's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 205/50R18 | 26.07" | 8.07" | +0.2% | 60.1 mph | Compare |
| 225/45R18 | 25.97" | 8.86" | −0.2% | 59.9 mph | Compare |
| 295/35R18 | 26.13" | 11.61" | +0.4% | 60.2 mph | Compare |
| 285/35R18 | 25.85" | 11.22" | −0.7% | 59.6 mph | Compare |
| 235/45R18 | 26.33" | 9.25" | +1.1% | 60.7 mph | Compare |
| 245/40R18 | 25.72" | 9.65" | −1.2% | 59.3 mph | Compare |
| 265/40R18 | 26.35" | 10.43" | +1.2% | 60.7 mph | Compare |
| 195/50R18 | 25.68" | 7.68" | −1.4% | 59.2 mph | Compare |
| 305/35R18 | 26.41" | 12.01" | +1.4% | 60.9 mph | Compare |
| 195/55R18 | 26.44" | 7.68" | +1.6% | 61.0 mph | Compare |
| 215/45R18 | 25.62" | 8.46" | −1.6% | 59.0 mph | Compare |
| 215/50R18 | 26.46" | 8.46" | +1.7% | 61.0 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 235/65R14 | 14" | 26.03" | 0.0% | Compare |
| 255/45R17 | 17" | 26.04" | 0.0% | Compare |
| 255/35R19 | 19" | 26.03" | 0.0% | Compare |
| 175/80R15 | 15" | 26.02" | 0.0% | Compare |
| 255/50R16 | 16" | 26.04" | 0.0% | Compare |
| 255/30R20 | 20" | 26.02" | 0.0% | Compare |
| 165/85R15 | 15" | 26.04" | 0.0% | Compare |
| 255/55R15 | 15" | 26.04" | 0.0% | Compare |
| 255/25R21 | 21" | 26.02" | 0.0% | Compare |
| 255/60R14 | 14" | 26.05" | +0.1% | Compare |
| 195/85R13 | 13" | 26.05" | +0.1% | Compare |
| 215/65R15 | 15" | 26.00" | −0.1% | Compare |
One size up or down
- 245/40R18narrower: 25.7" × 9.6"
- 265/40R18wider: 26.3" × 10.4"
- 255/35R18lower profile: 25.0" × 10.0"
- 255/45R18taller sidewall: 27.0" × 10.0"
Compare 255/40R18 with another size
Questions
- How tall is a 255/40R18 tire?
- A 255/40R18 tire is 26.0 inches tall (661 mm), calculated from the size. It is 10.0 inches wide with 4.0 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 255/40R18 mean?
- 255/40R18 means a tire 255 mm wide, with sidewalls 40% as tall as the tire is wide (102 mm), radial construction (R), for a 18 inch wheel.
- How many revolutions per mile does a 255/40R18 tire make?
- About 775 revolutions per mile, based on a circumference of 81.8 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 255/40R18 tire?
- Roughly 8.5" to 10.0". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 205/50R18 instead of 255/40R18?
- 205/50R18 is +0.04 inches (+0.2%) 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.