Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
180/55r18 vs 185/50r18 Tire Comparison Side By Side
  180/55-18 185/50-18 Difference
Diameter inches (mm) 25.8 (655.2) 25.28 (642.2) -0.51 (-13) -2%
Width inches (mm) 7.09 (180) 7.28 (185) 0.2 (5) 2.8%
Circum. inches (mm) 81.04 (2058.37) 79.43 (2017.53) -1.61 (-40.84) -2%
Sidewall Height inches (mm) 3.9 (99) 3.64 (92.5) -0.26 (-6.5) -6.6%
Revolutions per mile (km) 781.85 (485.82) 797.68 (495.65) 15.83 (9.83) 2%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.6 mph (31.55 km/h)
25 mph (40.23 km/h)24.5 mph (39.44 km/h)
30 mph (48.28 km/h)29.4 mph (47.32 km/h)
35 mph (56.33 km/h)34.31 mph (55.21 km/h)
40 mph (64.37 km/h)39.21 mph (63.1 km/h)
45 mph (72.42 km/h)44.11 mph (70.98 km/h)
50 mph (80.47 km/h)49.01 mph (78.87 km/h)
55 mph (88.51 km/h)53.91 mph (86.76 km/h)
60 mph (96.56 km/h)58.81 mph (94.64 km/h)
65 mph (104.61 km/h)63.71 mph (102.53 km/h)
70 mph (112.65 km/h)68.61 mph (110.42 km/h)
75 mph (120.7 km/h)73.51 mph (118.31 km/h)
80 mph (128.75 km/h)78.41 mph (126.19 km/h)
85 mph (136.79 km/h)83.31 mph (134.08 km/h)
90 mph (144.84 km/h)88.21 mph (141.97 km/h)
95 mph (152.89 km/h)93.12 mph (149.85 km/h)
100 mph (160.93 km/h)98.02 mph (157.74 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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