Tire Size Box

185/75R15 vs 205/75R15

205/75R15 compared with 185/75R15

+4.6% diameter, +0.8" width

205/75R15 is 27.11" tall vs 25.93". More than the 3% rule of thumb, so check carefully before switching.

25.9"15" rim5.5"7.3" wide
185/75R15 (solid) compared with 205/75R15 (dashed outline), drawn to scale

With 205/75R15 tires, when your speedometer says 60 mph you are really going

62.7 mph

205/75R15 is +1.18 inches (+4.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/75R15205/75R15Difference%
Overall diameter25.93"27.11"+1.18"+4.6%
Section width7.28"8.07"+0.79"+10.8%
Sidewall height5.46"6.05"+0.59"+10.8%
Circumference81.45"85.16"+3.71"+4.6%
Revolutions per mile777.9744.0−33.9−4.4%

Speedometer difference

If your vehicle came with 185/75R15 and you fit 205/75R15, 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 mph41.8 mph+1.8 mph
50 mph52.3 mph+2.3 mph
60 mph62.7 mph+2.7 mph
65 mph68.0 mph+3.0 mph
70 mph73.2 mph+3.2 mph
75 mph78.4 mph+3.4 mph
80 mph83.6 mph+3.6 mph

Each size on its own

Questions

Which is bigger, 185/75R15 or 205/75R15?
205/75R15 is taller by 1.18 inches (27.11" vs 25.93"). 205/75R15 is wider by 0.79 inches.
Can I replace 185/75R15 with 205/75R15?
It is not recommended without checking carefully. The diameter difference is +4.6%, 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 205/75R15 change my speedometer?
When your speedometer reads 60 mph with 205/75R15 fitted (calibrated for 185/75R15), your real speed is 62.7 mph. Your odometer will under-count miles by about 4.6%.
Will 205/75R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.59 inches of ground clearance at the axle.

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