Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
325/70r18 vs 33/12.5r18 Tire Comparison Side By Side
  325/70-18 33/12.5-18 Difference
Diameter inches (mm) 35.91 (912.2) 33.02 (838.8) -2.89 (-73.4) -8%
Width inches (mm) 12.8 (325) 12.52 (318) -0.28 (-7) -2.2%
Circum. inches (mm) 112.83 (2865.76) 103.75 (2635.17) -9.08 (-230.59) -8%
Sidewall Height inches (mm) 8.96 (227.5) 7.51 (190.8) -1.44 (-36.7) -16.1%
Revolutions per mile (km) 561.58 (348.95) 610.72 (379.48) 49.14 (30.53) 8.8%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)18.39 mph (29.6 km/h)
25 mph (40.23 km/h)22.99 mph (37 km/h)
30 mph (48.28 km/h)27.59 mph (44.4 km/h)
35 mph (56.33 km/h)32.18 mph (51.79 km/h)
40 mph (64.37 km/h)36.78 mph (59.19 km/h)
45 mph (72.42 km/h)41.38 mph (66.59 km/h)
50 mph (80.47 km/h)45.98 mph (73.99 km/h)
55 mph (88.51 km/h)50.57 mph (81.39 km/h)
60 mph (96.56 km/h)55.17 mph (88.79 km/h)
65 mph (104.61 km/h)59.77 mph (96.19 km/h)
70 mph (112.65 km/h)64.37 mph (103.59 km/h)
75 mph (120.7 km/h)68.97 mph (110.99 km/h)
80 mph (128.75 km/h)73.56 mph (118.39 km/h)
85 mph (136.79 km/h)78.16 mph (125.79 km/h)
90 mph (144.84 km/h)82.76 mph (133.19 km/h)
95 mph (152.89 km/h)87.36 mph (140.59 km/h)
100 mph (160.93 km/h)91.95 mph (147.99 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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