Tire Size Box

225/45R15 vs 245/45R15

245/45R15 compared with 225/45R15

+3.1% diameter, +0.8" width

245/45R15 is 23.68" tall vs 22.97". More than the 3% rule of thumb, so check carefully before switching.

23.0"15" rim4.0"8.9" wide
225/45R15 (solid) compared with 245/45R15 (dashed outline), drawn to scale

With 245/45R15 tires, when your speedometer says 60 mph you are really going

61.9 mph

245/45R15 is +0.71 inches (+3.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/45R15245/45R15Difference%
Overall diameter22.97"23.68"+0.71"+3.1%
Section width8.86"9.65"+0.79"+8.9%
Sidewall height3.99"4.34"+0.35"+8.9%
Circumference72.17"74.40"+2.23"+3.1%
Revolutions per mile877.9851.7−26.3−3.0%

Speedometer difference

If your vehicle came with 225/45R15 and you fit 245/45R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph30.9 mph+0.9 mph
40 mph41.2 mph+1.2 mph
50 mph51.5 mph+1.5 mph
60 mph61.9 mph+1.9 mph
65 mph67.0 mph+2.0 mph
70 mph72.2 mph+2.2 mph
75 mph77.3 mph+2.3 mph
80 mph82.5 mph+2.5 mph

Each size on its own

Questions

Which is bigger, 225/45R15 or 245/45R15?
245/45R15 is taller by 0.71 inches (23.68" vs 22.97"). 245/45R15 is wider by 0.79 inches.
Can I replace 225/45R15 with 245/45R15?
It is not recommended without checking carefully. The diameter difference is +3.1%, 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 245/45R15 change my speedometer?
When your speedometer reads 60 mph with 245/45R15 fitted (calibrated for 225/45R15), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.1%.
Will 245/45R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.35 inches of ground clearance at the axle.

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