255/55R18 tire size
A 255/55R18 tire stands 29.04 inches tall overall, on a 18-inch wheel, with a 140.3 mm sidewall and 255 mm of tread across. It turns roughly 694 times per mile.
- Overall diameter
- 29.04″
- 737.7 mm
- Sidewall height
- 140.3 mm
- 55% of 255 mm
- Circumference
- 91.2″
- 2,318 mm
- Revs per mile
- 694
- 431 per km
Reading the number
255 / 55 R 18 │ │ └─ rim diameter, 18 inches │ └──── aspect ratio, sidewall is 55% of width └──────── tread width, 255 mm sidewall = 255 × 0.55 = 140.25 mm diameter = (18 × 25.4) + (2 × 140.25) = 737.7 mm
Sizes that can replace 255/55R18
One rim step away, sorted by how close the rolling diameter stays.
Questions
›What does 255/55R18 mean?
255 is the tread width in millimetres. 55 is the aspect ratio, so the sidewall is 55% of 255 mm, or 140.3 mm. R means radial construction, and 18 is the wheel diameter in inches.
›How tall is a 255/55R18 tire?
29.04 inches, or 737.7 mm overall. That is the 18-inch rim plus a 140.3 mm sidewall at the top and another at the bottom.
›How many revolutions per mile does 255/55R18 do?
About 694 revolutions per mile, from a rolling circumference of 91.2 inches. Speedometers and odometers are calibrated against this figure, which is why changing size shifts both.
›What tires can replace 255/55R18?
Sizes within 3% of its rolling diameter and one rim step away, such as 235/65R17, 235/60R18, 235/55R19. Each is compared in full below.
Comparing against a size not listed? Open the calculator.