Tire Size Box

185/55R17 vs 185/65R17

185/65R17 compared with 185/55R17

+5.8% diameter, 0.0" width

185/65R17 is 26.47" tall vs 25.01". More than the 3% rule of thumb, so check carefully before switching.

25.0"17" rim4.0"7.3" wide
185/55R17 (solid) compared with 185/65R17 (dashed outline), drawn to scale

With 185/65R17 tires, when your speedometer says 60 mph you are really going

63.5 mph

185/65R17 is +1.46 inches (+5.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/55R17185/65R17Difference%
Overall diameter25.01"26.47"+1.46"+5.8%
Section width7.28"7.28"0.00"0.0%
Sidewall height4.01"4.73"+0.73"+18.2%
Circumference78.58"83.15"+4.58"+5.8%
Revolutions per mile806.3762.0−44.4−5.5%

Speedometer difference

If your vehicle came with 185/55R17 and you fit 185/65R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.2 mph+1.2 mph
30 mph31.7 mph+1.7 mph
40 mph42.3 mph+2.3 mph
50 mph52.9 mph+2.9 mph
60 mph63.5 mph+3.5 mph
65 mph68.8 mph+3.8 mph
70 mph74.1 mph+4.1 mph
75 mph79.4 mph+4.4 mph
80 mph84.7 mph+4.7 mph

Each size on its own

Questions

Which is bigger, 185/55R17 or 185/65R17?
185/65R17 is taller by 1.46 inches (26.47" vs 25.01"). 185/55R17 is the same width.
Can I replace 185/55R17 with 185/65R17?
It is not recommended without checking carefully. The diameter difference is +5.8%, 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 185/65R17 change my speedometer?
When your speedometer reads 60 mph with 185/65R17 fitted (calibrated for 185/55R17), your real speed is 63.5 mph. Your odometer will under-count miles by about 5.8%.
Will 185/65R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.73 inches of ground clearance at the axle.

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