235/40R18 Tire Size Specifications & Compatible Vehicles
Overall Diameter
645.2 mm
Section Width
235 mm
Sidewall Height
94.0 mm
Circumference
2027.0 mm
Revs/Mile
794
Rim Diameter
18"
Inch Equivalent
25.4x9.3R18
Rim Width (ETRTO)
7.0" – 9.0"
Compatible Vehicles
The following vehicles use 235/40R18 tires from the factory:
Alternative Tire Sizes
These tire sizes are within 3% overall diameter of 235/40R18 and may be used as replacements:
Popular Comparisons
See how 235/40R18 compares to other common tire sizes:
Understanding 235/40R18
The tire size 235/40R18 means the tire has a section width of 235mm, an aspect ratio of 40% (the sidewall height is 40% of the width), and fits a 18-inch rim.
Sidewall Height = 235 x 0.4 = 94.0 mm
Overall Diameter = (94.0 x 2) + (18 x 25.4) = 645.2 mm
Circumference = 645.2 x π = 2027.0 mm
Overall Diameter = (94.0 x 2) + (18 x 25.4) = 645.2 mm
Circumference = 645.2 x π = 2027.0 mm
Frequently Asked Questions
The 235/40R18 tire size is used on 5 vehicle trims including the 2025 Honda Civic, 2025 Honda Civic, 2024 Honda Civic and 2 more.
A 235/40R18 tire has an overall diameter of 645.2mm (25.4 inches). The sidewall height is 94.0mm, and the total circumference is 2027mm.
For 235/40R18 tires, the ETRTO recommended rim width is 8.0". The acceptable range is 7.0" minimum to 9.0" maximum. Using a rim outside this range can cause improper bead seating and unsafe handling.
Yes, as long as the replacement tire overall diameter is within 3% of the 235/40R18 645.2mm diameter. Compatible alternatives include 305/35R17, 325/25R19, 265/45R16. Use our Tire Size Calculator to compare any two sizes.