Tire Size Box

185/75R17 vs 205/75R17

205/75R17 compared with 185/75R17

+4.2% diameter, +0.8" width

205/75R17 is 29.11" tall vs 27.93". More than the 3% rule of thumb, so check carefully before switching.

27.9"17" rim5.5"7.3" wide
185/75R17 (solid) compared with 205/75R17 (dashed outline), drawn to scale

With 205/75R17 tires, when your speedometer says 60 mph you are really going

62.5 mph

205/75R17 is +1.18 inches (+4.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/75R17205/75R17Difference%
Overall diameter27.93"29.11"+1.18"+4.2%
Section width7.28"8.07"+0.79"+10.8%
Sidewall height5.46"6.05"+0.59"+10.8%
Circumference87.73"91.44"+3.71"+4.2%
Revolutions per mile722.2692.9−29.3−4.1%

Speedometer difference

If your vehicle came with 185/75R17 and you fit 205/75R17, 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 mph73.0 mph+3.0 mph
75 mph78.2 mph+3.2 mph
80 mph83.4 mph+3.4 mph

Each size on its own

Questions

Which is bigger, 185/75R17 or 205/75R17?
205/75R17 is taller by 1.18 inches (29.11" vs 27.93"). 205/75R17 is wider by 0.79 inches.
Can I replace 185/75R17 with 205/75R17?
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 205/75R17 change my speedometer?
When your speedometer reads 60 mph with 205/75R17 fitted (calibrated for 185/75R17), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.2%.
Will 205/75R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.59 inches of ground clearance at the axle.

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