Tire Size Box

185/65R15 vs 205/65R15

205/65R15 compared with 185/65R15

+4.2% diameter, +0.8" width

205/65R15 is 25.49" tall vs 24.47". More than the 3% rule of thumb, so check carefully before switching.

24.5"15" rim4.7"7.3" wide
185/65R15 (solid) compared with 205/65R15 (dashed outline), drawn to scale

With 205/65R15 tires, when your speedometer says 60 mph you are really going

62.5 mph

205/65R15 is +1.02 inches (+4.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/65R15205/65R15Difference%
Overall diameter24.47"25.49"+1.02"+4.2%
Section width7.28"8.07"+0.79"+10.8%
Sidewall height4.73"5.25"+0.51"+10.8%
Circumference76.87"80.09"+3.22"+4.2%
Revolutions per mile824.2791.2−33.1−4.0%

Speedometer difference

If your vehicle came with 185/65R15 and you fit 205/65R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.3 mph+1.3 mph
40 mph41.7 mph+1.7 mph
50 mph52.1 mph+2.1 mph
60 mph62.5 mph+2.5 mph
65 mph67.7 mph+2.7 mph
70 mph72.9 mph+2.9 mph
75 mph78.1 mph+3.1 mph
80 mph83.3 mph+3.3 mph

Each size on its own

Questions

Which is bigger, 185/65R15 or 205/65R15?
205/65R15 is taller by 1.02 inches (25.49" vs 24.47"). 205/65R15 is wider by 0.79 inches.
Can I replace 185/65R15 with 205/65R15?
It is not recommended without checking carefully. The diameter difference is +4.2%, 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 205/65R15 change my speedometer?
When your speedometer reads 60 mph with 205/65R15 fitted (calibrated for 185/65R15), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.2%.
Will 205/65R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.51 inches of ground clearance at the axle.

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