Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
120/85r18 vs 325/35r18 Tire Comparison Side By Side
  120/85-18 325/35-18 Difference
Diameter inches (mm) 26.03 (661.2) 26.96 (684.7) 0.93 (23.5) 3.6%
Width inches (mm) 4.72 (120) 12.8 (325) 8.07 (205) 170.8%
Circum. inches (mm) 81.78 (2077.22) 84.69 (2151.05) 2.91 (73.83) 3.6%
Sidewall Height inches (mm) 4.02 (102) 4.48 (113.75) 0.46 (11.75) 11.5%
Revolutions per mile (km) 774.76 (481.41) 748.17 (464.89) -26.59 (-16.52) -3.4%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)20.71 mph (33.33 km/h)
25 mph (40.23 km/h)25.89 mph (41.66 km/h)
30 mph (48.28 km/h)31.07 mph (50 km/h)
35 mph (56.33 km/h)36.24 mph (58.33 km/h)
40 mph (64.37 km/h)41.42 mph (66.66 km/h)
45 mph (72.42 km/h)46.6 mph (74.99 km/h)
50 mph (80.47 km/h)51.78 mph (83.33 km/h)
55 mph (88.51 km/h)56.95 mph (91.66 km/h)
60 mph (96.56 km/h)62.13 mph (99.99 km/h)
65 mph (104.61 km/h)67.31 mph (108.33 km/h)
70 mph (112.65 km/h)72.49 mph (116.66 km/h)
75 mph (120.7 km/h)77.67 mph (124.99 km/h)
80 mph (128.75 km/h)82.84 mph (133.32 km/h)
85 mph (136.79 km/h)88.02 mph (141.66 km/h)
90 mph (144.84 km/h)93.2 mph (149.99 km/h)
95 mph (152.89 km/h)98.38 mph (158.32 km/h)
100 mph (160.93 km/h)103.55 mph (166.65 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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