Tire Size Box

205/65R18 vs 225/65R18

225/65R18 compared with 205/65R18

+3.6% diameter, +0.8" width

225/65R18 is 29.52" tall vs 28.49". More than the 3% rule of thumb, so check carefully before switching.

28.5"18" rim5.2"8.1" wide
205/65R18 (solid) compared with 225/65R18 (dashed outline), drawn to scale

With 225/65R18 tires, when your speedometer says 60 mph you are really going

62.2 mph

225/65R18 is +1.02 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

205/65R18225/65R18Difference%
Overall diameter28.49"29.52"+1.02"+3.6%
Section width8.07"8.86"+0.79"+9.8%
Sidewall height5.25"5.76"+0.51"+9.8%
Circumference89.51"92.73"+3.22"+3.6%
Revolutions per mile707.8683.3−24.5−3.5%

Speedometer difference

If your vehicle came with 205/65R18 and you fit 225/65R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.4 mph+1.4 mph
50 mph51.8 mph+1.8 mph
60 mph62.2 mph+2.2 mph
65 mph67.3 mph+2.3 mph
70 mph72.5 mph+2.5 mph
75 mph77.7 mph+2.7 mph
80 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 205/65R18 or 225/65R18?
225/65R18 is taller by 1.02 inches (29.52" vs 28.49"). 225/65R18 is wider by 0.79 inches.
Can I replace 205/65R18 with 225/65R18?
It is not recommended without checking carefully. The diameter difference is +3.6%, 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 225/65R18 change my speedometer?
When your speedometer reads 60 mph with 225/65R18 fitted (calibrated for 205/65R18), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.6%.
Will 225/65R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.51 inches of ground clearance at the axle.

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