Tire Size Box

285/45R15 vs 285/55R15

285/55R15 compared with 285/45R15

+8.9% diameter, 0.0" width

285/55R15 is 27.34" tall vs 25.10". More than the 3% rule of thumb, so check carefully before switching.

25.1"15" rim5.0"11.2" wide
285/45R15 (solid) compared with 285/55R15 (dashed outline), drawn to scale

With 285/55R15 tires, when your speedometer says 60 mph you are really going

65.4 mph

285/55R15 is +2.24 inches (+8.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/45R15285/55R15Difference%
Overall diameter25.10"27.34"+2.24"+8.9%
Section width11.22"11.22"0.00"0.0%
Sidewall height5.05"6.17"+1.12"+22.2%
Circumference78.85"85.90"+7.05"+8.9%
Revolutions per mile803.6737.6−66.0−8.2%

Speedometer difference

If your vehicle came with 285/45R15 and you fit 285/55R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.8 mph+1.8 mph
30 mph32.7 mph+2.7 mph
40 mph43.6 mph+3.6 mph
50 mph54.5 mph+4.5 mph
60 mph65.4 mph+5.4 mph
65 mph70.8 mph+5.8 mph
70 mph76.3 mph+6.3 mph
75 mph81.7 mph+6.7 mph
80 mph87.2 mph+7.2 mph

Each size on its own

Questions

Which is bigger, 285/45R15 or 285/55R15?
285/55R15 is taller by 2.24 inches (27.34" vs 25.10"). 285/45R15 is the same width.
Can I replace 285/45R15 with 285/55R15?
It is not recommended without checking carefully. The diameter difference is +8.9%, 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 285/55R15 change my speedometer?
When your speedometer reads 60 mph with 285/55R15 fitted (calibrated for 285/45R15), your real speed is 65.4 mph. Your odometer will under-count miles by about 8.9%.
Will 285/55R15 lift my vehicle?
Ride height changes by half the diameter difference: +1.12 inches of ground clearance at the axle.

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