255/65R18 tire size in inches

Nominal 255/65R18 dimensions

Overall diameter

31.05 in788.7 mm

Section width

10.04 in255 mm

Sidewall height

6.53 in165.8 mm

Circumference

97.55 in2,477.8 mm

Rim diameter

18 in

Revolutions per mile

650nominal, from geometric circumference

Inch notation

31.1x10.0R18approximate

Where 255/65R18 fits

• Inch class: 31.05 in is within 0.1 in of a true 31 inches, so the 31-inch label is close to exact.
• Profile: the 18-inch rim plus two 6.53 in sidewalls make up the overall diameter, and the sidewalls are 42% of it. At 65 series that is a tall profile: the extra sidewall absorbs more of each bump and flexes more in corners.
• Same 18-inch rim: the next taller catalog size is 265/65R18 (31.56 in, +1.65%) and the next shorter is 265/60R18 (30.52 in, -1.71%).
• Same 255 mm width: the closest in diameter are 255/65R17 (30.05 in, -3.22%), 255/70R16 (30.06 in, -3.21%), 255/70R17 (31.06 in, +0.01%), 255/75R16 (31.06 in, +0.03%). At the same width, a different profile or rim changes sidewall height and overall diameter, not section width.

Reading the marking: 255 is the section width in millimeters, 65 is the sidewall height as a percentage of that width, and R18 means radial construction for a 18-inch rim. Percentages are measured from 255/65R18.

Similar sizes on other rim diameters

Within 3% of 255/65R18's overall diameter, nearest first. The speed column is the actual speed when a speedometer calibrated for 255/65R18 reads 60 mph.

For a size without a comparison page, open 255/65R18 in the calculator and enter that size as the proposed tire.

Important: These results compare nominal dimensions. They do not confirm vehicle fitment. Actual clearance varies by tire model, approved rim width, wheel construction, suspension, alignment, body tolerances, steering angle, load, and brake geometry. Verify load and speed ratings and physically test-fit the complete setup before driving.

Physical checks before changing size

• Approved rim-width range for the exact tire model
• Load index and speed rating equal to or greater than vehicle requirements
• Brake-caliper, hub, and wheel-fastener compatibility
• Fender, liner, suspension, and full-lock steering clearance
• Clearance at full compression and under expected load
• Alignment, tire pressure, and manufacturer guidance
• Professional inspection when variance or clearance is uncertain

Published comparisons for 255/65R18

None keeps the 18-inch rim; each one changes wheel diameter. Diameter changes are measured from 255/65R18.