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 38/12.5r15 Tire Comparison Side By Side
  38/15.5-20 38/12.5-15 Difference
Diameter inches (mm) 37.99 (965.04) 38.04 (966.12) 0.04 (1.08) 0.1%
Width inches (mm) 15.51 (394) 12.52 (318) -2.99 (-76) -19.3%
Circum. inches (mm) 119.36 (3031.76) 119.49 (3035.16) 0.13 (3.39) 0.1%
Sidewall Height inches (mm) 9 (228.52) 11.52 (292.56) 2.52 (64.04) 28%
Revolutions per mile (km) 530.83 (329.84) 530.23 (329.47) -0.59 (-0.37) -0.1%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)20.02 mph (32.22 km/h)
25 mph (40.23 km/h)25.03 mph (40.28 km/h)
30 mph (48.28 km/h)30.03 mph (48.33 km/h)
35 mph (56.33 km/h)35.04 mph (56.39 km/h)
40 mph (64.37 km/h)40.04 mph (64.45 km/h)
45 mph (72.42 km/h)45.05 mph (72.5 km/h)
50 mph (80.47 km/h)50.06 mph (80.56 km/h)
55 mph (88.51 km/h)55.06 mph (88.61 km/h)
60 mph (96.56 km/h)60.07 mph (96.67 km/h)
65 mph (104.61 km/h)65.07 mph (104.72 km/h)
70 mph (112.65 km/h)70.08 mph (112.78 km/h)
75 mph (120.7 km/h)75.08 mph (120.84 km/h)
80 mph (128.75 km/h)80.09 mph (128.89 km/h)
85 mph (136.79 km/h)85.1 mph (136.95 km/h)
90 mph (144.84 km/h)90.1 mph (145 km/h)
95 mph (152.89 km/h)95.11 mph (153.06 km/h)
100 mph (160.93 km/h)100.11 mph (161.11 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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