Section Width305 mm (12.0")
Aspect Ratio55%
Rim Diameter18"
Overall Diameter793 mm (31.2")
Sidewall Height168 mm
Circumference2490 mm
305/55R18 — Buy Tires

Everything to know about the 305/55R18 tire size

Size geometry

A 305/55R18 tire has a 305mm section width and a 55% aspect ratio, mounted on a 18-inch rim. Sidewall height works out to 167.8mm (6.60") and overall outside diameter is 792.7mm (31.21"). At highway speed the tire completes about 402 revolutions per kilometre — your speedometer and odometer were calibrated against this number.

Direct substitute sizes

If 305/55R18 is unavailable, the closest same-diameter substitutes on the same rim are 295/57R18 and 315/53R18. Both keep your speedometer reading within 1% — safe for daily use, ABS, and stability control. Always verify load and speed ratings before swapping.

Plus / minus sizing options

For a 305/55R18 you can upsize to 315/49R19 (plus-one) to fit a larger wheel without changing the speedometer reading, or downsize to 295/61R17 (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 305/55R18 tire size from the factory. Aftermarket fitment depends on rim width, offset, and clearance — match these specs to your wheel before purchasing tires.

Vehicles Using 305/55R18

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