Tire Size Box

185/70R17 vs 205/70R17

205/70R17 compared with 185/70R17

+4.1% diameter, +0.8" width

205/70R17 is 28.30" tall vs 27.20". More than the 3% rule of thumb, so check carefully before switching.

27.2"17" rim5.1"7.3" wide
185/70R17 (solid) compared with 205/70R17 (dashed outline), drawn to scale

With 205/70R17 tires, when your speedometer says 60 mph you are really going

62.4 mph

205/70R17 is +1.10 inches (+4.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/70R17205/70R17Difference%
Overall diameter27.20"28.30"+1.10"+4.1%
Section width7.28"8.07"+0.79"+10.8%
Sidewall height5.10"5.65"+0.55"+10.8%
Circumference85.44"88.90"+3.46"+4.1%
Revolutions per mile741.6712.7−28.9−3.9%

Speedometer difference

If your vehicle came with 185/70R17 and you fit 205/70R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.2 mph+1.2 mph
40 mph41.6 mph+1.6 mph
50 mph52.0 mph+2.0 mph
60 mph62.4 mph+2.4 mph
65 mph67.6 mph+2.6 mph
70 mph72.8 mph+2.8 mph
75 mph78.0 mph+3.0 mph
80 mph83.2 mph+3.2 mph

Each size on its own

Questions

Which is bigger, 185/70R17 or 205/70R17?
205/70R17 is taller by 1.10 inches (28.30" vs 27.20"). 205/70R17 is wider by 0.79 inches.
Can I replace 185/70R17 with 205/70R17?
It is not recommended without checking carefully. The diameter difference is +4.1%, 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 205/70R17 change my speedometer?
When your speedometer reads 60 mph with 205/70R17 fitted (calibrated for 185/70R17), your real speed is 62.4 mph. Your odometer will under-count miles by about 4.1%.
Will 205/70R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.55 inches of ground clearance at the axle.

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