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 315/50r20 Tire Comparison Side By Side
  38/15.5-20 315/50-20 Difference
Diameter inches (mm) 37.99 (965.04) 32.4 (823) -5.59 (-142.04) -14.7%
Width inches (mm) 15.51 (394) 12.4 (315) -3.11 (-79) -20.1%
Circum. inches (mm) 119.36 (3031.76) 101.79 (2585.53) -17.57 (-446.23) -14.7%
Sidewall Height inches (mm) 9 (228.52) 6.2 (157.5) -2.8 (-71.02) -31.1%
Revolutions per mile (km) 530.83 (329.84) 622.44 (386.77) 91.61 (56.93) 17.3%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)17.06 mph (27.45 km/h)
25 mph (40.23 km/h)21.32 mph (34.31 km/h)
30 mph (48.28 km/h)25.58 mph (41.17 km/h)
35 mph (56.33 km/h)29.85 mph (48.04 km/h)
40 mph (64.37 km/h)34.11 mph (54.9 km/h)
45 mph (72.42 km/h)38.38 mph (61.76 km/h)
50 mph (80.47 km/h)42.64 mph (68.62 km/h)
55 mph (88.51 km/h)46.9 mph (75.49 km/h)
60 mph (96.56 km/h)51.17 mph (82.35 km/h)
65 mph (104.61 km/h)55.43 mph (89.21 km/h)
70 mph (112.65 km/h)59.7 mph (96.07 km/h)
75 mph (120.7 km/h)63.96 mph (102.94 km/h)
80 mph (128.75 km/h)68.23 mph (109.8 km/h)
85 mph (136.79 km/h)72.49 mph (116.66 km/h)
90 mph (144.84 km/h)76.75 mph (123.52 km/h)
95 mph (152.89 km/h)81.02 mph (130.39 km/h)
100 mph (160.93 km/h)85.28 mph (137.25 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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