Tire Size Box

185/80R15 vs 205/80R15

205/80R15 compared with 185/80R15

+4.7% diameter, +0.8" width

205/80R15 is 27.91" tall vs 26.65". More than the 3% rule of thumb, so check carefully before switching.

26.7"15" rim5.8"7.3" wide
185/80R15 (solid) compared with 205/80R15 (dashed outline), drawn to scale

With 205/80R15 tires, when your speedometer says 60 mph you are really going

62.8 mph

205/80R15 is +1.26 inches (+4.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/80R15205/80R15Difference%
Overall diameter26.65"27.91"+1.26"+4.7%
Section width7.28"8.07"+0.79"+10.8%
Sidewall height5.83"6.46"+0.63"+10.8%
Circumference83.73"87.69"+3.96"+4.7%
Revolutions per mile756.7722.5−34.2−4.5%

Speedometer difference

If your vehicle came with 185/80R15 and you fit 205/80R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.9 mph+0.9 mph
30 mph31.4 mph+1.4 mph
40 mph41.9 mph+1.9 mph
50 mph52.4 mph+2.4 mph
60 mph62.8 mph+2.8 mph
65 mph68.1 mph+3.1 mph
70 mph73.3 mph+3.3 mph
75 mph78.5 mph+3.5 mph
80 mph83.8 mph+3.8 mph

Each size on its own

Questions

Which is bigger, 185/80R15 or 205/80R15?
205/80R15 is taller by 1.26 inches (27.91" vs 26.65"). 205/80R15 is wider by 0.79 inches.
Can I replace 185/80R15 with 205/80R15?
It is not recommended without checking carefully. The diameter difference is +4.7%, 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 205/80R15 change my speedometer?
When your speedometer reads 60 mph with 205/80R15 fitted (calibrated for 185/80R15), your real speed is 62.8 mph. Your odometer will under-count miles by about 4.7%.
Will 205/80R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.63 inches of ground clearance at the axle.

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