32.1" tall, 10.8" wide, 7.0" sidewall
A 275/65R18 tire is 32.1 inches (815 mm) tall and 10.8 inches wide. The sidewall is 65% of the width, 7.0 inches, on a 18-inch wheel, and the tire turns about 629 times per mile.
In flotation terms that is about 32.1x10.8R18. People often call it a 32-inch tire.
The size most often compared with it is 275/70R18, which is 1.1" taller (+3.4%). At an indicated 60 mph you would be doing 62.0 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 275/65R18 | |
|---|---|---|---|---|---|
| 255/70R18 | 32.1" | 10.0" | 7.0" | −0.1% | compare |
| 295/60R18 | 31.9" | 11.6" | 7.0" | −0.4% | |
| 265/65R18 | 31.6" | 10.4" | 6.8" | −1.6% | compare |
| 285/65R18 | 32.6" | 11.2" | 7.3" | +1.6% | compare |
| 265/70R18 | 32.6" | 10.4" | 7.3" | +1.7% | compare |
| 285/60R18 | 31.5" | 11.2" | 6.7" | −1.9% | |
| 255/75R18 | 33.1" | 10.0" | 7.5" | +3.1% | |
| 295/65R18 | 33.1" | 11.6" | 7.5" | +3.2% | |
| 275/60R18 | 31.0" | 10.8" | 6.5" | −3.4% | |
| 275/70R18 | 33.2" | 10.8" | 7.6" | +3.4% | compare |
Sizes within 2% of 32.1" on 16" or 17" or 20" wheels.
| Size | Diameter | Width | Sidewall | vs 275/65R18 | |
|---|---|---|---|---|---|
| 255/80R16 | 32.1" | 10.0" | 8.0" | −0.0% | |
| 255/75R17 | 32.1" | 10.0" | 7.5" | −0.0% | |
| 295/65R17 | 32.1" | 11.6" | 7.5" | +0.1% | |
| 255/60R20 | 32.0" | 10.0" | 6.0" | −0.1% | |
| 305/50R20 | 32.0" | 12.0" | 6.0" | −0.2% | |
| 275/70R17 | 32.2" | 10.8" | 7.6" | +0.3% | compare |
Actual speed when the speedometer is calibrated for 275/65R18.
| Speedometer shows | on 275/70R18 | on 255/70R18 | on 265/65R18 |
|---|---|---|---|
| 30 mph | 31.0 mph | 30.0 mph | 29.5 mph |
| 45 mph | 46.5 mph | 45.0 mph | 44.3 mph |
| 60 mph | 62.0 mph | 60.0 mph | 59.0 mph |
| 70 mph | 72.4 mph | 70.0 mph | 68.9 mph |
32.1 inches (815 mm). The sidewall is 7.0 inches.
10.8 inches (275 mm) section width, measured sidewall to sidewall.
About 32.1x10.8R18.
275/70R18 is +3.4% in diameter, more than the common 3% guideline, so expect a speedometer error and check clearance. It is 0.0" wider.