235/40R18 tire size in inches
A 235/40R18 tire measures
25.4" tall × 9.3" wide
3.70" sidewall on a 18" wheel. 794 revolutions per mile.
235/40R18 means a tire 235 mm wide, with sidewalls 40% as tall as the tire is wide (94 mm), radial construction (R), for a 18 inch wheel.
235/40R18 specs
| Overall diameter (height) | 25.40 inches (645 mm) |
|---|---|
| Section width | 9.25 inches (235 mm) |
| Sidewall height | 3.70 inches (94 mm) |
| Wheel (rim) diameter | 18 inches |
| Circumference | 79.8 inches (2,027 mm) |
| Revolutions per mile | 794 |
| Revolutions per kilometer | 493 |
| Approximate rim width | 7.5" to 9.0" |
| In inches (flotation style) | 25.4x9.3R18 |
| 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 235/40R18 on a 18" wheel
These 18" sizes are within 3% of 235/40R18's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 265/35R18 | 25.30" | 10.43" | −0.4% | 59.8 mph | Compare |
| 205/45R18 | 25.26" | 8.07" | −0.5% | 59.7 mph | Compare |
| 275/35R18 | 25.58" | 10.83" | +0.7% | 60.4 mph | Compare |
| 215/45R18 | 25.62" | 8.46" | +0.9% | 60.5 mph | Compare |
| 195/50R18 | 25.68" | 7.68" | +1.1% | 60.7 mph | Compare |
| 225/40R18 | 25.09" | 8.86" | −1.2% | 59.3 mph | Compare |
| 245/40R18 | 25.72" | 9.65" | +1.2% | 60.7 mph | Compare |
| 255/35R18 | 25.03" | 10.04" | −1.5% | 59.1 mph | Compare |
| 285/35R18 | 25.85" | 11.22" | +1.8% | 61.1 mph | Compare |
| 195/45R18 | 24.91" | 7.68" | −1.9% | 58.8 mph | Compare |
| 225/45R18 | 25.97" | 8.86" | +2.2% | 61.3 mph | Compare |
| 215/40R18 | 24.77" | 8.46" | −2.5% | 58.5 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 225/70R13 | 13" | 25.40" | 0.0% | Compare |
| 305/35R17 | 17" | 25.41" | 0.0% | Compare |
| 325/25R19 | 19" | 25.40" | 0.0% | Compare |
| 165/80R15 | 15" | 25.39" | 0.0% | Compare |
| 275/25R20 | 20" | 25.41" | 0.0% | Compare |
| 265/45R16 | 16" | 25.39" | 0.0% | Compare |
| 185/85R13 | 13" | 25.38" | −0.1% | Compare |
| 225/25R21 | 21" | 25.43" | +0.1% | Compare |
| 265/50R15 | 15" | 25.43" | +0.1% | Compare |
| 195/55R17 | 17" | 25.44" | +0.2% | Compare |
| 205/40R19 | 19" | 25.46" | +0.2% | Compare |
| 265/40R17 | 17" | 25.35" | −0.2% | Compare |
One size up or down
- 225/40R18narrower: 25.1" × 8.9"
- 245/40R18wider: 25.7" × 9.6"
- 235/35R18lower profile: 24.5" × 9.3"
- 235/45R18taller sidewall: 26.3" × 9.3"
Compare 235/40R18 with another size
Questions
- How tall is a 235/40R18 tire?
- A 235/40R18 tire is 25.4 inches tall (645 mm), calculated from the size. It is 9.3 inches wide with 3.7 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 235/40R18 mean?
- 235/40R18 means a tire 235 mm wide, with sidewalls 40% as tall as the tire is wide (94 mm), radial construction (R), for a 18 inch wheel.
- How many revolutions per mile does a 235/40R18 tire make?
- About 794 revolutions per mile, based on a circumference of 79.8 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 235/40R18 tire?
- Roughly 7.5" to 9.0". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 265/35R18 instead of 235/40R18?
- 265/35R18 is −0.10 inches (−0.4%) in overall diameter, so at an indicated 60 mph you would be doing 59.8 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.