Tire Size Box

185/55R16 vs 185/65R16

185/65R16 compared with 185/55R16

+6.1% diameter, 0.0" width

185/65R16 is 25.47" tall vs 24.01". More than the 3% rule of thumb, so check carefully before switching.

24.0"16" rim4.0"7.3" wide
185/55R16 (solid) compared with 185/65R16 (dashed outline), drawn to scale

With 185/65R16 tires, when your speedometer says 60 mph you are really going

63.6 mph

185/65R16 is +1.46 inches (+6.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

185/55R16185/65R16Difference%
Overall diameter24.01"25.47"+1.46"+6.1%
Section width7.28"7.28"0.00"0.0%
Sidewall height4.01"4.73"+0.73"+18.2%
Circumference75.44"80.01"+4.58"+6.1%
Revolutions per mile839.9791.9−48.0−5.7%

Speedometer difference

If your vehicle came with 185/55R16 and you fit 185/65R16, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.2 mph+1.2 mph
30 mph31.8 mph+1.8 mph
40 mph42.4 mph+2.4 mph
50 mph53.0 mph+3.0 mph
60 mph63.6 mph+3.6 mph
65 mph68.9 mph+3.9 mph
70 mph74.2 mph+4.2 mph
75 mph79.5 mph+4.5 mph
80 mph84.9 mph+4.9 mph

Each size on its own

Questions

Which is bigger, 185/55R16 or 185/65R16?
185/65R16 is taller by 1.46 inches (25.47" vs 24.01"). 185/55R16 is the same width.
Can I replace 185/55R16 with 185/65R16?
It is not recommended without checking carefully. The diameter difference is +6.1%, 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 185/65R16 change my speedometer?
When your speedometer reads 60 mph with 185/65R16 fitted (calibrated for 185/55R16), your real speed is 63.6 mph. Your odometer will under-count miles by about 6.1%.
Will 185/65R16 lift my vehicle?
Ride height changes by half the diameter difference: +0.73 inches of ground clearance at the axle.

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