Tire Size Box

185/45R17 vs 205/45R17

205/45R17 compared with 185/45R17

+3.0% diameter, +0.8" width

205/45R17 is 24.26" tall vs 23.56". More than the 3% rule of thumb, so check carefully before switching.

23.6"17" rim3.3"7.3" wide
185/45R17 (solid) compared with 205/45R17 (dashed outline), drawn to scale

With 205/45R17 tires, when your speedometer says 60 mph you are really going

61.8 mph

205/45R17 is +0.71 inches (+3.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/45R17205/45R17Difference%
Overall diameter23.56"24.26"+0.71"+3.0%
Section width7.28"8.07"+0.79"+10.8%
Sidewall height3.28"3.63"+0.35"+10.8%
Circumference74.00"76.23"+2.23"+3.0%
Revolutions per mile856.2831.2−25.0−2.9%

Speedometer difference

If your vehicle came with 185/45R17 and you fit 205/45R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph30.9 mph+0.9 mph
40 mph41.2 mph+1.2 mph
50 mph51.5 mph+1.5 mph
60 mph61.8 mph+1.8 mph
65 mph67.0 mph+2.0 mph
70 mph72.1 mph+2.1 mph
75 mph77.3 mph+2.3 mph
80 mph82.4 mph+2.4 mph

Each size on its own

Questions

Which is bigger, 185/45R17 or 205/45R17?
205/45R17 is taller by 0.71 inches (24.26" vs 23.56"). 205/45R17 is wider by 0.79 inches.
Can I replace 185/45R17 with 205/45R17?
It is not recommended without checking carefully. The diameter difference is +3.0%, 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 205/45R17 change my speedometer?
When your speedometer reads 60 mph with 205/45R17 fitted (calibrated for 185/45R17), your real speed is 61.8 mph. Your odometer will under-count miles by about 3.0%.
Will 205/45R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.35 inches of ground clearance at the axle.

Other comparisons