How tall is a 255/45R18 tire?

A 255/45R18 has a nominal overall diameter of 27.04 inches (687 mm), calculated as the 18-inch wheel plus two sidewalls. This is the unloaded figure — a fitted tire sits fractionally shorter under the weight of the vehicle.

What wheel size does a 255/45R18 tire fit?

A 255/45R18 fits a wheel of 18 inches in diameter. The wheel also has to be within the rim width range the manufacturer publishes for this size, which is printed in the tire's spec sheet.

What do the numbers in 255/45R18 mean?

255 is the section width in millimetres. 45 is the aspect ratio — the sidewall is 45% of the width, so 114.8 mm here. R marks the construction (radial). 18 is the wheel diameter in inches.

Size Dimensions & Specs

Tires Size 255/45R18

Dimensions, specs, and every size 255/45R18 tire currently in stock

Overall Height

27.04"

687 mm · calculated

Section Width

255 mm

10.04 inches

Sidewall Height

4.52"

114.8 mm · 45% profile

Wheel Diameter

18"

457.2 mm

255/45R18 Specifications

Read directly from the size code. Load index, speed rating, and rim width range vary by model.

Specification	Imperial	Metric
Section width	10.04 in	255 mm
Aspect ratio	45%	—
Sidewall height	4.52 in	114.8 mm
Overall diameter (calculated)	27.04 in	687 mm
Wheel / rim diameter	18 in	457.2 mm
Construction	Radial	—

What does 255/45R18 mean?

Reading the code on your sidewall

Section width

255 mm

The distance from sidewall to sidewall across the tire's widest point.

Aspect ratio

45% profile

The sidewall stands 45% of the section width, which is 114.8 mm on this size.

Construction (R)

Radial

The body plies run across the tire at right angles to the direction of travel.

Wheel diameter

18 in

Fits a wheel measuring 18 inches across.

255/45R18 Questions & Answers

Dimensions and fitment guidelines for size 255/45R18

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