815/39R18 Tire Size Specifications
This tire size 815/39R18 fits 0 vehicles in our database.
Everything to know about the 815/39R18 tire size
Size geometry
A 815/39R18 tire has a 815mm section width and a 39% aspect ratio, mounted on a 18-inch rim. Sidewall height works out to 317.9mm (12.51") and overall outside diameter is 1092.9mm (43.03"). At highway speed the tire completes about 291 revolutions per kilometre â your speedometer and odometer were calibrated against this number.
Direct substitute sizes
If 815/39R18 is unavailable, the closest same-diameter substitutes on the same rim are 805/39R18 and 825/39R18. Both keep your speedometer reading within 1% â safe for daily use, ABS, and stability control. Always verify load and speed ratings before swapping.
Plus / minus sizing options
For a 815/39R18 you can upsize to 825/37R19 (plus-one) to fit a larger wheel without changing the speedometer reading, or downsize to 805/41R17 (minus-one) for a softer ride or winter setup. Both stay inside the Âą3% diameter tolerance that ABS and TPMS systems expect.
Vehicle compatibility
0 vehicles in our database run the 815/39R18 tire size from the factory. Aftermarket fitment depends on rim width, offset, and clearance â match these specs to your wheel before purchasing tires.
Vehicles Using 815/39R18
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