Tire Size Box

225/55R15 vs 245/55R15

245/55R15 compared with 225/55R15

+3.5% diameter, +0.8" width

245/55R15 is 25.61" tall vs 24.74". More than the 3% rule of thumb, so check carefully before switching.

24.7"15" rim4.9"8.9" wide
225/55R15 (solid) compared with 245/55R15 (dashed outline), drawn to scale

With 245/55R15 tires, when your speedometer says 60 mph you are really going

62.1 mph

245/55R15 is +0.87 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/55R15245/55R15Difference%
Overall diameter24.74"25.61"+0.87"+3.5%
Section width8.86"9.65"+0.79"+8.9%
Sidewall height4.87"5.31"+0.43"+8.9%
Circumference77.74"80.46"+2.72"+3.5%
Revolutions per mile815.1787.5−27.6−3.4%

Speedometer difference

If your vehicle came with 225/55R15 and you fit 245/55R15, 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 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.5 mph+2.5 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 225/55R15 or 245/55R15?
245/55R15 is taller by 0.87 inches (25.61" vs 24.74"). 245/55R15 is wider by 0.79 inches.
Can I replace 225/55R15 with 245/55R15?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 245/55R15 change my speedometer?
When your speedometer reads 60 mph with 245/55R15 fitted (calibrated for 225/55R15), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 245/55R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.43 inches of ground clearance at the axle.

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