Tire size 235/40R18 in inches and mm

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First published: 04/10/2023 - Updated on: 04/29/2024
Attribute American European
Rim Size 18 in 457.2 mm
Width 9.3 in 235 mm
Sidewall 3.7 in 94 mm
Diameter 25.4 in 645.2 mm
Circumference 79.8 in 2026.9 mm
Revolutions per Mile 794 493 per km

Tire size 235/40R18 explained in detail

The tire size 235/40R18 has the following key attributes: diameter, width, wheel (rim), sidewall, circumference, and revs per mile (rpm). Each of these attributes plays a critical role in determining the tire’s performance, appearance, and compatibility with the vehicle.

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235/40R18 Diameter

The diameter for the 235/40R18 tire is 25.4 in (645.2 mm). The diameter represents the distance from one end of the tire to the other, passing through the center. It is essential to choose a tire with the correct diameter, as it can impact the overall performance, ride comfort, and vehicle clearance.

235/40R18 Width

With a width of 9.3 in (235 mm), the 235/40R18 tire’s width measures the distance between the inner and outer sidewalls at the widest point. The width of a tire affects its contact patch with the road, which can influence traction, handling, and fuel efficiency.

235/40R18 Wheel (Rim)

The 235/40R18 tire is designed to fit a wheel (or rim) with a diameter of 18 in (457.2 mm). The wheel supports the tire and provides a mounting point to the vehicle’s suspension. It is crucial to select a tire that matches the wheel size, as improper fitment can lead to safety concerns and reduced performance.

235/40R18 Sidewall

The sidewall of the 235/40R18 tire measures 3.7 in (94 mm) from the edge of the wheel to the outer surface of the tire. The sidewall height affects ride comfort, handling, and the tire’s ability to absorb road irregularities. A shorter sidewall generally offers better handling and a firmer ride, while a taller sidewall can provide a smoother, more comfortable ride.

235/40R18 Circumference

The circumference of the 235/40R18 tire is 79.8 in (2026.9 mm), which represents the total distance around the outer edge of the tire. The circumference can impact the tire’s rolling resistance, which affects fuel efficiency and overall performance.

235/40R18 Revs per Mile (RPM)

The 235/40R18 tire has 794 rpm (493.4 per km), which indicates the number of times the tire rotates as the vehicle travels one mile. This value is useful for calculating speedometer and odometer accuracy, as well as determining the impact of tire size on the vehicle’s gearing and performance.

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Please note that these values are specific to the tire size 235/40R18. It is crucial to choose the correct tire size for your vehicle, as improper fitment can lead to reduced performance, safety concerns, and even damage to your vehicle. Always consult your vehicle’s owner’s manual or a professional tire retailer to determine the appropriate tire size for your application.

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