Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
40/12.5r20 vs 37/12.5r17 Tire Comparison Side By Side
  40/12.5-20 37/12.5-17 Difference
Diameter inches (mm) 40.03 (1016.8) 37.03 (940.6) -3 (-76.2) -7.5%
Width inches (mm) 12.52 (318) 12.52 (318) 0 (0) 0%
Circum. inches (mm) 125.76 (3194.37) 116.34 (2954.98) -9.42 (-239.39) -7.5%
Sidewall Height inches (mm) 10.02 (254.4) 10.02 (254.4) 0 (0) 0%
Revolutions per mile (km) 503.81 (313.05) 544.62 (338.41) 40.81 (25.36) 8.1%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)18.5 mph (29.77 km/h)
25 mph (40.23 km/h)23.13 mph (37.22 km/h)
30 mph (48.28 km/h)27.75 mph (44.66 km/h)
35 mph (56.33 km/h)32.38 mph (52.11 km/h)
40 mph (64.37 km/h)37 mph (59.55 km/h)
45 mph (72.42 km/h)41.63 mph (66.99 km/h)
50 mph (80.47 km/h)46.25 mph (74.44 km/h)
55 mph (88.51 km/h)50.88 mph (81.88 km/h)
60 mph (96.56 km/h)55.5 mph (89.32 km/h)
65 mph (104.61 km/h)60.13 mph (96.77 km/h)
70 mph (112.65 km/h)64.75 mph (104.21 km/h)
75 mph (120.7 km/h)69.38 mph (111.66 km/h)
80 mph (128.75 km/h)74 mph (119.1 km/h)
85 mph (136.79 km/h)78.63 mph (126.54 km/h)
90 mph (144.84 km/h)83.26 mph (133.99 km/h)
95 mph (152.89 km/h)87.88 mph (141.43 km/h)
100 mph (160.93 km/h)92.51 mph (148.87 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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