Tire Size Box

225/65R20 vs 245/65R20

245/65R20 compared with 225/65R20

+3.2% diameter, +0.8" width

245/65R20 is 32.54" tall vs 31.52". More than the 3% rule of thumb, so check carefully before switching.

31.5"20" rim5.8"8.9" wide
225/65R20 (solid) compared with 245/65R20 (dashed outline), drawn to scale

With 245/65R20 tires, when your speedometer says 60 mph you are really going

61.9 mph

245/65R20 is +1.02 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/65R20245/65R20Difference%
Overall diameter31.52"32.54"+1.02"+3.2%
Section width8.86"9.65"+0.79"+8.9%
Sidewall height5.76"6.27"+0.51"+8.9%
Circumference99.01"102.23"+3.22"+3.2%
Revolutions per mile639.9619.8−20.1−3.1%

Speedometer difference

If your vehicle came with 225/65R20 and you fit 245/65R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph61.9 mph+1.9 mph
65 mph67.1 mph+2.1 mph
70 mph72.3 mph+2.3 mph
75 mph77.4 mph+2.4 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 225/65R20 or 245/65R20?
245/65R20 is taller by 1.02 inches (32.54" vs 31.52"). 245/65R20 is wider by 0.79 inches.
Can I replace 225/65R20 with 245/65R20?
It is not recommended without checking carefully. The diameter difference is +3.2%, 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 245/65R20 change my speedometer?
When your speedometer reads 60 mph with 245/65R20 fitted (calibrated for 225/65R20), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 245/65R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.51 inches of ground clearance at the axle.

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