Tire Size Box

225/60R18 vs 245/60R18

245/60R18 compared with 225/60R18

+3.3% diameter, +0.8" width

245/60R18 is 29.57" tall vs 28.63". More than the 3% rule of thumb, so check carefully before switching.

28.6"18" rim5.3"8.9" wide
225/60R18 (solid) compared with 245/60R18 (dashed outline), drawn to scale

With 245/60R18 tires, when your speedometer says 60 mph you are really going

62.0 mph

245/60R18 is +0.94 inches (+3.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/60R18245/60R18Difference%
Overall diameter28.63"29.57"+0.94"+3.3%
Section width8.86"9.65"+0.79"+8.9%
Sidewall height5.31"5.79"+0.47"+8.9%
Circumference89.94"92.91"+2.97"+3.3%
Revolutions per mile704.4681.9−22.5−3.2%

Speedometer difference

If your vehicle came with 225/60R18 and you fit 245/60R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.7 mph+1.7 mph
60 mph62.0 mph+2.0 mph
65 mph67.1 mph+2.1 mph
70 mph72.3 mph+2.3 mph
75 mph77.5 mph+2.5 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 225/60R18 or 245/60R18?
245/60R18 is taller by 0.94 inches (29.57" vs 28.63"). 245/60R18 is wider by 0.79 inches.
Can I replace 225/60R18 with 245/60R18?
It is not recommended without checking carefully. The diameter difference is +3.3%, 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 245/60R18 change my speedometer?
When your speedometer reads 60 mph with 245/60R18 fitted (calibrated for 225/60R18), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.3%.
Will 245/60R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.47 inches of ground clearance at the axle.

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