Tire Size Box

185/55R15 vs 205/55R15

205/55R15 compared with 185/55R15

+3.8% diameter, +0.8" width

205/55R15 is 23.88" tall vs 23.01". More than the 3% rule of thumb, so check carefully before switching.

23.0"15" rim4.0"7.3" wide
185/55R15 (solid) compared with 205/55R15 (dashed outline), drawn to scale

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

62.3 mph

205/55R15 is +0.87 inches (+3.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/55R15205/55R15Difference%
Overall diameter23.01"23.88"+0.87"+3.8%
Section width7.28"8.07"+0.79"+10.8%
Sidewall height4.01"4.44"+0.43"+10.8%
Circumference72.29"75.01"+2.72"+3.8%
Revolutions per mile876.4844.6−31.8−3.6%

Speedometer difference

If your vehicle came with 185/55R15 and you fit 205/55R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.9 mph+1.9 mph
60 mph62.3 mph+2.3 mph
65 mph67.4 mph+2.4 mph
70 mph72.6 mph+2.6 mph
75 mph77.8 mph+2.8 mph
80 mph83.0 mph+3.0 mph

Each size on its own

Questions

Which is bigger, 185/55R15 or 205/55R15?
205/55R15 is taller by 0.87 inches (23.88" vs 23.01"). 205/55R15 is wider by 0.79 inches.
Can I replace 185/55R15 with 205/55R15?
It is not recommended without checking carefully. The diameter difference is +3.8%, 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 185/55R15), your real speed is 62.3 mph. Your odometer will under-count miles by about 3.8%.
Will 205/55R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.43 inches of ground clearance at the axle.

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