Tire Size Box

205/45R17 vs 205/55R17

205/55R17 compared with 205/45R17

+6.7% diameter, 0.0" width

205/55R17 is 25.88" tall vs 24.26". More than the 3% rule of thumb, so check carefully before switching.

24.3"17" rim3.6"8.1" wide
205/45R17 (solid) compared with 205/55R17 (dashed outline), drawn to scale

With 205/55R17 tires, when your speedometer says 60 mph you are really going

64.0 mph

205/55R17 is +1.61 inches (+6.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

205/45R17205/55R17Difference%
Overall diameter24.26"25.88"+1.61"+6.7%
Section width8.07"8.07"0.00"0.0%
Sidewall height3.63"4.44"+0.81"+22.2%
Circumference76.23"81.30"+5.07"+6.7%
Revolutions per mile831.2779.4−51.8−6.2%

Speedometer difference

If your vehicle came with 205/45R17 and you fit 205/55R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.3 mph+1.3 mph
30 mph32.0 mph+2.0 mph
40 mph42.7 mph+2.7 mph
50 mph53.3 mph+3.3 mph
60 mph64.0 mph+4.0 mph
65 mph69.3 mph+4.3 mph
70 mph74.7 mph+4.7 mph
75 mph80.0 mph+5.0 mph
80 mph85.3 mph+5.3 mph

Each size on its own

Questions

Which is bigger, 205/45R17 or 205/55R17?
205/55R17 is taller by 1.61 inches (25.88" vs 24.26"). 205/45R17 is the same width.
Can I replace 205/45R17 with 205/55R17?
It is not recommended without checking carefully. The diameter difference is +6.7%, 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 205/55R17 change my speedometer?
When your speedometer reads 60 mph with 205/55R17 fitted (calibrated for 205/45R17), your real speed is 64.0 mph. Your odometer will under-count miles by about 6.7%.
Will 205/55R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.81 inches of ground clearance at the axle.

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