Tire Size Box

205/45R15 vs 205/55R15

205/55R15 compared with 205/45R15

+7.3% diameter, 0.0" width

205/55R15 is 23.88" tall vs 22.26". More than the 3% rule of thumb, so check carefully before switching.

22.3"15" rim3.6"8.1" wide
205/45R15 (solid) compared with 205/55R15 (dashed outline), drawn to scale

With 205/55R15 tires, when your speedometer says 60 mph you are really going

64.4 mph

205/55R15 is +1.61 inches (+7.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

205/45R15205/55R15Difference%
Overall diameter22.26"23.88"+1.61"+7.3%
Section width8.07"8.07"0.00"0.0%
Sidewall height3.63"4.44"+0.81"+22.2%
Circumference69.94"75.01"+5.07"+7.3%
Revolutions per mile905.9844.6−61.2−6.8%

Speedometer difference

If your vehicle came with 205/45R15 and you fit 205/55R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.5 mph+1.5 mph
30 mph32.2 mph+2.2 mph
40 mph42.9 mph+2.9 mph
50 mph53.6 mph+3.6 mph
60 mph64.4 mph+4.4 mph
65 mph69.7 mph+4.7 mph
70 mph75.1 mph+5.1 mph
75 mph80.4 mph+5.4 mph
80 mph85.8 mph+5.8 mph

Each size on its own

Questions

Which is bigger, 205/45R15 or 205/55R15?
205/55R15 is taller by 1.61 inches (23.88" vs 22.26"). 205/45R15 is the same width.
Can I replace 205/45R15 with 205/55R15?
It is not recommended without checking carefully. The diameter difference is +7.3%, 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 205/55R15 change my speedometer?
When your speedometer reads 60 mph with 205/55R15 fitted (calibrated for 205/45R15), your real speed is 64.4 mph. Your odometer will under-count miles by about 7.3%.
Will 205/55R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.81 inches of ground clearance at the axle.

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