Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
145/60r20 vs 125/80r18 Tire Comparison Side By Side
  145/60-20 125/80-18 Difference
Diameter inches (mm) 26.85 (682) 25.87 (657.2) -0.98 (-24.8) -3.6%
Width inches (mm) 5.71 (145) 4.92 (125) -0.79 (-20) -13.8%
Circum. inches (mm) 84.35 (2142.57) 81.29 (2064.65) -3.07 (-77.91) -3.6%
Sidewall Height inches (mm) 3.43 (87) 3.94 (100) 0.51 (13) 14.9%
Revolutions per mile (km) 751.13 (466.73) 779.47 (484.34) 28.34 (17.61) 3.8%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.27 mph (31.02 km/h)
25 mph (40.23 km/h)24.09 mph (38.77 km/h)
30 mph (48.28 km/h)28.91 mph (46.52 km/h)
35 mph (56.33 km/h)33.73 mph (54.28 km/h)
40 mph (64.37 km/h)38.55 mph (62.03 km/h)
45 mph (72.42 km/h)43.36 mph (69.79 km/h)
50 mph (80.47 km/h)48.18 mph (77.54 km/h)
55 mph (88.51 km/h)53 mph (85.3 km/h)
60 mph (96.56 km/h)57.82 mph (93.05 km/h)
65 mph (104.61 km/h)62.64 mph (100.8 km/h)
70 mph (112.65 km/h)67.45 mph (108.56 km/h)
75 mph (120.7 km/h)72.27 mph (116.31 km/h)
80 mph (128.75 km/h)77.09 mph (124.07 km/h)
85 mph (136.79 km/h)81.91 mph (131.82 km/h)
90 mph (144.84 km/h)86.73 mph (139.57 km/h)
95 mph (152.89 km/h)91.55 mph (147.33 km/h)
100 mph (160.93 km/h)96.36 mph (155.08 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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