Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
120/100r18 vs 120/80r18 Tire Comparison Side By Side
  120/100-18 120/80-18 Difference
Diameter inches (mm) 27.45 (697.2) 25.56 (649.2) -1.89 (-48) -6.9%
Width inches (mm) 4.72 (120) 4.72 (120) 0 (0) 0%
Circum. inches (mm) 86.23 (2190.32) 80.3 (2039.52) -5.94 (-150.8) -6.9%
Sidewall Height inches (mm) 4.72 (120) 3.78 (96) -0.94 (-24) -20%
Revolutions per mile (km) 734.75 (456.55) 789.08 (490.31) 54.33 (33.76) 7.4%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)18.62 mph (29.97 km/h)
25 mph (40.23 km/h)23.28 mph (37.46 km/h)
30 mph (48.28 km/h)27.93 mph (44.96 km/h)
35 mph (56.33 km/h)32.59 mph (52.45 km/h)
40 mph (64.37 km/h)37.25 mph (59.94 km/h)
45 mph (72.42 km/h)41.9 mph (67.43 km/h)
50 mph (80.47 km/h)46.56 mph (74.93 km/h)
55 mph (88.51 km/h)51.21 mph (82.42 km/h)
60 mph (96.56 km/h)55.87 mph (89.91 km/h)
65 mph (104.61 km/h)60.52 mph (97.41 km/h)
70 mph (112.65 km/h)65.18 mph (104.9 km/h)
75 mph (120.7 km/h)69.84 mph (112.39 km/h)
80 mph (128.75 km/h)74.49 mph (119.88 km/h)
85 mph (136.79 km/h)79.15 mph (127.38 km/h)
90 mph (144.84 km/h)83.8 mph (134.87 km/h)
95 mph (152.89 km/h)88.46 mph (142.36 km/h)
100 mph (160.93 km/h)93.12 mph (149.85 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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