Tire Size Box

225/75R15 vs 245/75R15

245/75R15 compared with 225/75R15

+4.2% diameter, +0.8" width

245/75R15 is 29.47" tall vs 28.29". More than the 3% rule of thumb, so check carefully before switching.

28.3"15" rim6.6"8.9" wide
225/75R15 (solid) compared with 245/75R15 (dashed outline), drawn to scale

With 245/75R15 tires, when your speedometer says 60 mph you are really going

62.5 mph

245/75R15 is +1.18 inches (+4.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/75R15245/75R15Difference%
Overall diameter28.29"29.47"+1.18"+4.2%
Section width8.86"9.65"+0.79"+8.9%
Sidewall height6.64"7.23"+0.59"+8.9%
Circumference88.87"92.58"+3.71"+4.2%
Revolutions per mile713.0684.4−28.6−4.0%

Speedometer difference

If your vehicle came with 225/75R15 and you fit 245/75R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.3 mph+1.3 mph
40 mph41.7 mph+1.7 mph
50 mph52.1 mph+2.1 mph
60 mph62.5 mph+2.5 mph
65 mph67.7 mph+2.7 mph
70 mph72.9 mph+2.9 mph
75 mph78.1 mph+3.1 mph
80 mph83.3 mph+3.3 mph

Each size on its own

Questions

Which is bigger, 225/75R15 or 245/75R15?
245/75R15 is taller by 1.18 inches (29.47" vs 28.29"). 245/75R15 is wider by 0.79 inches.
Can I replace 225/75R15 with 245/75R15?
It is not recommended without checking carefully. The diameter difference is +4.2%, 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 245/75R15 change my speedometer?
When your speedometer reads 60 mph with 245/75R15 fitted (calibrated for 225/75R15), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.2%.
Will 245/75R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.59 inches of ground clearance at the axle.

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