Tire Size Box

225/75R17 vs 245/75R17

245/75R17 compared with 225/75R17

+3.9% diameter, +0.8" width

245/75R17 is 31.47" tall vs 30.29". More than the 3% rule of thumb, so check carefully before switching.

30.3"17" rim6.6"8.9" wide
225/75R17 (solid) compared with 245/75R17 (dashed outline), drawn to scale

With 245/75R17 tires, when your speedometer says 60 mph you are really going

62.3 mph

245/75R17 is +1.18 inches (+3.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/75R17245/75R17Difference%
Overall diameter30.29"31.47"+1.18"+3.9%
Section width8.86"9.65"+0.79"+8.9%
Sidewall height6.64"7.23"+0.59"+8.9%
Circumference95.15"98.86"+3.71"+3.9%
Revolutions per mile665.9640.9−25.0−3.8%

Speedometer difference

If your vehicle came with 225/75R17 and you fit 245/75R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.2 mph+1.2 mph
40 mph41.6 mph+1.6 mph
50 mph51.9 mph+1.9 mph
60 mph62.3 mph+2.3 mph
65 mph67.5 mph+2.5 mph
70 mph72.7 mph+2.7 mph
75 mph77.9 mph+2.9 mph
80 mph83.1 mph+3.1 mph

Each size on its own

Questions

Which is bigger, 225/75R17 or 245/75R17?
245/75R17 is taller by 1.18 inches (31.47" vs 30.29"). 245/75R17 is wider by 0.79 inches.
Can I replace 225/75R17 with 245/75R17?
It is not recommended without checking carefully. The diameter difference is +3.9%, 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 245/75R17 change my speedometer?
When your speedometer reads 60 mph with 245/75R17 fitted (calibrated for 225/75R17), your real speed is 62.3 mph. Your odometer will under-count miles by about 3.9%.
Will 245/75R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.59 inches of ground clearance at the axle.

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