Tire Size Box

225/55R17 vs 245/55R17

245/55R17 compared with 225/55R17

+3.2% diameter, +0.8" width

245/55R17 is 27.61" tall vs 26.74". More than the 3% rule of thumb, so check carefully before switching.

26.7"17" rim4.9"8.9" wide
225/55R17 (solid) compared with 245/55R17 (dashed outline), drawn to scale

With 245/55R17 tires, when your speedometer says 60 mph you are really going

61.9 mph

245/55R17 is +0.87 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/55R17245/55R17Difference%
Overall diameter26.74"27.61"+0.87"+3.2%
Section width8.86"9.65"+0.79"+8.9%
Sidewall height4.87"5.31"+0.43"+8.9%
Circumference84.02"86.74"+2.72"+3.2%
Revolutions per mile754.1730.5−23.7−3.1%

Speedometer difference

If your vehicle came with 225/55R17 and you fit 245/55R17, 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, 225/55R17 or 245/55R17?
245/55R17 is taller by 0.87 inches (27.61" vs 26.74"). 245/55R17 is wider by 0.79 inches.
Can I replace 225/55R17 with 245/55R17?
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 245/55R17 change my speedometer?
When your speedometer reads 60 mph with 245/55R17 fitted (calibrated for 225/55R17), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 245/55R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.43 inches of ground clearance at the axle.

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