Tire Size Box

185/85R15 vs 205/85R15

205/85R15 compared with 185/85R15

+4.9% diameter, +0.8" width

205/85R15 is 28.72" tall vs 27.38". More than the 3% rule of thumb, so check carefully before switching.

27.4"15" rim6.2"7.3" wide
185/85R15 (solid) compared with 205/85R15 (dashed outline), drawn to scale

With 205/85R15 tires, when your speedometer says 60 mph you are really going

62.9 mph

205/85R15 is +1.34 inches (+4.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/85R15205/85R15Difference%
Overall diameter27.38"28.72"+1.34"+4.9%
Section width7.28"8.07"+0.79"+10.8%
Sidewall height6.19"6.86"+0.67"+10.8%
Circumference86.02"90.23"+4.21"+4.9%
Revolutions per mile736.5702.2−34.3−4.7%

Speedometer difference

If your vehicle came with 185/85R15 and you fit 205/85R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.0 mph+1.0 mph
30 mph31.5 mph+1.5 mph
40 mph42.0 mph+2.0 mph
50 mph52.4 mph+2.4 mph
60 mph62.9 mph+2.9 mph
65 mph68.2 mph+3.2 mph
70 mph73.4 mph+3.4 mph
75 mph78.7 mph+3.7 mph
80 mph83.9 mph+3.9 mph

Each size on its own

Questions

Which is bigger, 185/85R15 or 205/85R15?
205/85R15 is taller by 1.34 inches (28.72" vs 27.38"). 205/85R15 is wider by 0.79 inches.
Can I replace 185/85R15 with 205/85R15?
It is not recommended without checking carefully. The diameter difference is +4.9%, 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 205/85R15 change my speedometer?
When your speedometer reads 60 mph with 205/85R15 fitted (calibrated for 185/85R15), your real speed is 62.9 mph. Your odometer will under-count miles by about 4.9%.
Will 205/85R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.67 inches of ground clearance at the axle.

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