26.7" tall, 10.8" wide, 4.3" sidewall
A 275/40R18 tire is 26.7 inches (677 mm) tall and 10.8 inches wide. The sidewall is 40% of the width, 4.3 inches, on a 18-inch wheel, and the tire turns about 756 times per mile.
In flotation terms that is about 26.7x10.8R18. People often call it a 27-inch tire.
The size most often compared with it is 275/35R18, which is 1.1" shorter (−4.1%). At an indicated 60 mph you would be doing 57.6 mph on it, more than the 3% change many shops use as a limit.
| Current | New | Difference |
|---|
| Shows | Actual speed |
|---|
Same 18" wheel, within 20 mm of width and 10 points of aspect ratio.
| Size | Diameter | Width | Sidewall | vs 275/40R18 | |
|---|---|---|---|---|---|
| 265/40R18 | 26.3" | 10.4" | 4.2" | −1.2% | |
| 285/40R18 | 27.0" | 11.2" | 4.5" | +1.2% | |
| 255/45R18 | 27.0" | 10.0" | 4.5" | +1.4% | |
| 295/35R18 | 26.1" | 11.6" | 4.1" | −2.0% | |
| 295/40R18 | 27.3" | 11.6" | 4.6" | +2.4% | |
| 255/40R18 | 26.0" | 10.0" | 4.0" | −2.4% | |
| 285/35R18 | 25.9" | 11.2" | 3.9" | −3.0% | |
| 275/35R18 | 25.6" | 10.8" | 3.8" | −4.1% | compare |
| 275/45R18 | 27.7" | 10.8" | 4.9" | +4.1% | |
| 265/35R18 | 25.3" | 10.4" | 3.7" | −5.1% |
Sizes within 2% of 26.7" on 17" or 19" or 20" wheels.
| Size | Diameter | Width | Sidewall | vs 275/40R18 | |
|---|---|---|---|---|---|
| 205/60R17 | 26.7" | 8.1" | 4.8" | +0.1% | |
| 305/40R17 | 26.6" | 12.0" | 4.8" | −0.2% | |
| 285/35R19 | 26.9" | 11.2" | 3.9" | +0.7% | |
| 295/30R20 | 27.0" | 11.6" | 3.5" | +1.2% | |
| 255/35R20 | 27.0" | 10.0" | 3.5" | +1.4% | |
| 295/40R17 | 26.3" | 11.6" | 4.6" | −1.4% |
Actual speed when the speedometer is calibrated for 275/40R18.
| Speedometer shows | on 275/35R18 | on 265/40R18 | on 285/40R18 |
|---|---|---|---|
| 30 mph | 28.8 mph | 29.6 mph | 30.4 mph |
| 45 mph | 43.2 mph | 44.5 mph | 45.5 mph |
| 60 mph | 57.6 mph | 59.3 mph | 60.7 mph |
| 70 mph | 67.2 mph | 69.2 mph | 70.8 mph |
26.7 inches (677 mm). The sidewall is 4.3 inches.
10.8 inches (275 mm) section width, measured sidewall to sidewall.
About 26.7x10.8R18.
275/35R18 is −4.1% in diameter, more than the common 3% guideline, so expect a speedometer error and check clearance. It is 0.0" wider.