Tire Size Box

285/50R15 vs 185/70R16

185/70R16 compared with 285/50R15

−0.1% diameter, −3.9" width

185/70R16 is 26.20" tall vs 26.22". Within the 3% rule, so usually interchangeable.

26.2"15" rim5.6"11.2" wide
285/50R15 (solid) compared with 185/70R16 (dashed outline), drawn to scale

With 185/70R16 tires, when your speedometer says 60 mph you are really going

59.9 mph

185/70R16 is −0.02 inches (−0.1%) in overall diameter. That is within the 3% most shops and makers allow.

285/50R15185/70R16Difference%
Overall diameter26.22"26.20"−0.02"−0.1%
Section width11.22"7.28"−3.94"−35.1%
Sidewall height5.61"5.10"−0.51"−9.1%
Circumference82.37"82.30"−0.07"−0.1%
Revolutions per mile769.2769.9+0.7+0.1%

Speedometer difference

If your vehicle came with 285/50R15 and you fit 185/70R16, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.0 mph0.0 mph
30 mph30.0 mph0.0 mph
40 mph40.0 mph0.0 mph
50 mph50.0 mph0.0 mph
60 mph59.9 mph−0.1 mph
65 mph64.9 mph−0.1 mph
70 mph69.9 mph−0.1 mph
75 mph74.9 mph−0.1 mph
80 mph79.9 mph−0.1 mph

Each size on its own

Questions

Which is bigger, 285/50R15 or 185/70R16?
285/50R15 is taller by 0.02 inches (26.22" vs 26.20"). 285/50R15 is wider by 3.94 inches.
Can I replace 285/50R15 with 185/70R16?
Usually, yes. The diameter difference is −0.1%, inside the 3% rule of thumb most tire shops use. Check that the wider or taller tire clears your suspension and fenders, and that its load index meets your placard.
How much will 185/70R16 change my speedometer?
When your speedometer reads 60 mph with 185/70R16 fitted (calibrated for 285/50R15), your real speed is 59.9 mph. Your odometer will over-count miles by about 0.1%.
Will 185/70R16 lift my vehicle?
Ride height changes by half the diameter difference: −0.01 inches of ground clearance at the axle.

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