Tire Size Box

205/50R18 vs 225/50R18

225/50R18 compared with 205/50R18

+3.0% diameter, +0.8" width

225/50R18 is 26.86" tall vs 26.07". More than the 3% rule of thumb, so check carefully before switching.

26.1"18" rim4.0"8.1" wide
205/50R18 (solid) compared with 225/50R18 (dashed outline), drawn to scale

With 225/50R18 tires, when your speedometer says 60 mph you are really going

61.8 mph

225/50R18 is +0.79 inches (+3.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

205/50R18225/50R18Difference%
Overall diameter26.07"26.86"+0.79"+3.0%
Section width8.07"8.86"+0.79"+9.8%
Sidewall height4.04"4.43"+0.39"+9.8%
Circumference81.90"84.38"+2.47"+3.0%
Revolutions per mile773.6750.9−22.7−2.9%

Speedometer difference

If your vehicle came with 205/50R18 and you fit 225/50R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph30.9 mph+0.9 mph
40 mph41.2 mph+1.2 mph
50 mph51.5 mph+1.5 mph
60 mph61.8 mph+1.8 mph
65 mph67.0 mph+2.0 mph
70 mph72.1 mph+2.1 mph
75 mph77.3 mph+2.3 mph
80 mph82.4 mph+2.4 mph

Each size on its own

Questions

Which is bigger, 205/50R18 or 225/50R18?
225/50R18 is taller by 0.79 inches (26.86" vs 26.07"). 225/50R18 is wider by 0.79 inches.
Can I replace 205/50R18 with 225/50R18?
It is not recommended without checking carefully. The diameter difference is +3.0%, more than the 3% most shops and makers allow. It will throw off the speedometer and may affect ABS, stability control and clearance.
How much will 225/50R18 change my speedometer?
When your speedometer reads 60 mph with 225/50R18 fitted (calibrated for 205/50R18), your real speed is 61.8 mph. Your odometer will under-count miles by about 3.0%.
Will 225/50R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.39 inches of ground clearance at the axle.

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