Section Width635 mm (25.0")
Aspect Ratio50%
Rim Diameter18"
Overall Diameter1092 mm (43.0")
Sidewall Height318 mm
Circumference3431 mm
635/50R18 — Buy Tires

Everything to know about the 635/50R18 tire size

Size geometry

A 635/50R18 tire has a 635mm section width and a 50% aspect ratio, mounted on a 18-inch rim. Sidewall height works out to 317.5mm (12.50") and overall outside diameter is 1092.2mm (43.00"). At highway speed the tire completes about 291 revolutions per kilometre — your speedometer and odometer were calibrated against this number.

Direct substitute sizes

If 635/50R18 is unavailable, the closest same-diameter substitutes on the same rim are 625/51R18 and 645/49R18. 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 635/50R18 you can upsize to 645/47R19 (plus-one) to fit a larger wheel without changing the speedometer reading, or downsize to 625/53R17 (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 635/50R18 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 635/50R18

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