Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
38/15.5r20 vs 37/13.5r20 Tire Comparison Side By Side
  38/15.5-20 37/13.5-20 Difference
Diameter inches (mm) 37.99 (965.04) 37.01 (940.18) -0.98 (-24.86) -2.6%
Width inches (mm) 15.51 (394) 13.5 (343) -2.01 (-51) -12.9%
Circum. inches (mm) 119.36 (3031.76) 116.29 (2953.66) -3.07 (-78.1) -2.6%
Sidewall Height inches (mm) 9 (228.52) 8.51 (216.09) -0.49 (-12.43) -5.4%
Revolutions per mile (km) 530.83 (329.84) 544.86 (338.56) 14.04 (8.72) 2.6%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.48 mph (31.36 km/h)
25 mph (40.23 km/h)24.36 mph (39.2 km/h)
30 mph (48.28 km/h)29.23 mph (47.04 km/h)
35 mph (56.33 km/h)34.1 mph (54.88 km/h)
40 mph (64.37 km/h)38.97 mph (62.72 km/h)
45 mph (72.42 km/h)43.84 mph (70.56 km/h)
50 mph (80.47 km/h)48.71 mph (78.39 km/h)
55 mph (88.51 km/h)53.58 mph (86.23 km/h)
60 mph (96.56 km/h)58.45 mph (94.07 km/h)
65 mph (104.61 km/h)63.33 mph (101.91 km/h)
70 mph (112.65 km/h)68.2 mph (109.75 km/h)
75 mph (120.7 km/h)73.07 mph (117.59 km/h)
80 mph (128.75 km/h)77.94 mph (125.43 km/h)
85 mph (136.79 km/h)82.81 mph (133.27 km/h)
90 mph (144.84 km/h)87.68 mph (141.11 km/h)
95 mph (152.89 km/h)92.55 mph (148.95 km/h)
100 mph (160.93 km/h)97.42 mph (156.79 km/h)

Gear Ratio / RPMs for New Tire (@ 65 mph)
2.35 2.73 2.94 3.07 3.21 3.31 3.42 3.55 3.73 3.91 4.11 4.27 4.56 4.88 5.13 5.29 5.38 5.71 6.17 7.17
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