Tire Size Box

165/60R15 vs 185/60R15

185/60R15 compared with 165/60R15

+4.1% diameter, +0.8" width

185/60R15 is 23.74" tall vs 22.80". More than the 3% rule of thumb, so check carefully before switching.

22.8"15" rim3.9"6.5" wide
165/60R15 (solid) compared with 185/60R15 (dashed outline), drawn to scale

With 185/60R15 tires, when your speedometer says 60 mph you are really going

62.5 mph

185/60R15 is +0.94 inches (+4.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

165/60R15185/60R15Difference%
Overall diameter22.80"23.74"+0.94"+4.1%
Section width6.50"7.28"+0.79"+12.1%
Sidewall height3.90"4.37"+0.47"+12.1%
Circumference71.61"74.58"+2.97"+4.1%
Revolutions per mile884.7849.5−35.2−4.0%

Speedometer difference

If your vehicle came with 165/60R15 and you fit 185/60R15, 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 mph41.7 mph+1.7 mph
50 mph52.1 mph+2.1 mph
60 mph62.5 mph+2.5 mph
65 mph67.7 mph+2.7 mph
70 mph72.9 mph+2.9 mph
75 mph78.1 mph+3.1 mph
80 mph83.3 mph+3.3 mph

Each size on its own

Questions

Which is bigger, 165/60R15 or 185/60R15?
185/60R15 is taller by 0.94 inches (23.74" vs 22.80"). 185/60R15 is wider by 0.79 inches.
Can I replace 165/60R15 with 185/60R15?
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 185/60R15 change my speedometer?
When your speedometer reads 60 mph with 185/60R15 fitted (calibrated for 165/60R15), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.1%.
Will 185/60R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.47 inches of ground clearance at the axle.

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