Tire Size Box

225/45R15 vs 225/55R15

225/55R15 compared with 225/45R15

+7.7% diameter, 0.0" width

225/55R15 is 24.74" 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 225/55R15 (dashed outline), drawn to scale

With 225/55R15 tires, when your speedometer says 60 mph you are really going

64.6 mph

225/55R15 is +1.77 inches (+7.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/45R15225/55R15Difference%
Overall diameter22.97"24.74"+1.77"+7.7%
Section width8.86"8.86"0.00"0.0%
Sidewall height3.99"4.87"+0.89"+22.2%
Circumference72.17"77.74"+5.57"+7.7%
Revolutions per mile877.9815.1−62.9−7.2%

Speedometer difference

If your vehicle came with 225/45R15 and you fit 225/55R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.5 mph+1.5 mph
30 mph32.3 mph+2.3 mph
40 mph43.1 mph+3.1 mph
50 mph53.9 mph+3.9 mph
60 mph64.6 mph+4.6 mph
65 mph70.0 mph+5.0 mph
70 mph75.4 mph+5.4 mph
75 mph80.8 mph+5.8 mph
80 mph86.2 mph+6.2 mph

Each size on its own

Questions

Which is bigger, 225/45R15 or 225/55R15?
225/55R15 is taller by 1.77 inches (24.74" vs 22.97"). 225/45R15 is the same width.
Can I replace 225/45R15 with 225/55R15?
It is not recommended without checking carefully. The diameter difference is +7.7%, 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 225/55R15 change my speedometer?
When your speedometer reads 60 mph with 225/55R15 fitted (calibrated for 225/45R15), your real speed is 64.6 mph. Your odometer will under-count miles by about 7.7%.
Will 225/55R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.89 inches of ground clearance at the axle.

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