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 170/55r18 Tire Comparison Side By Side
  180/55-18 170/55-18 Difference
Diameter inches (mm) 25.8 (655.2) 25.36 (644.2) -0.43 (-11) -1.7%
Width inches (mm) 7.09 (180) 6.69 (170) -0.39 (-10) -5.6%
Circum. inches (mm) 81.04 (2058.37) 79.68 (2023.81) -1.36 (-34.56) -1.7%
Sidewall Height inches (mm) 3.9 (99) 3.68 (93.5) -0.22 (-5.5) -5.6%
Revolutions per mile (km) 781.85 (485.82) 795.2 (494.12) 13.35 (8.3) 1.7%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.66 mph (31.65 km/h)
25 mph (40.23 km/h)24.58 mph (39.56 km/h)
30 mph (48.28 km/h)29.5 mph (47.47 km/h)
35 mph (56.33 km/h)34.41 mph (55.38 km/h)
40 mph (64.37 km/h)39.33 mph (63.29 km/h)
45 mph (72.42 km/h)44.24 mph (71.2 km/h)
50 mph (80.47 km/h)49.16 mph (79.12 km/h)
55 mph (88.51 km/h)54.08 mph (87.03 km/h)
60 mph (96.56 km/h)58.99 mph (94.94 km/h)
65 mph (104.61 km/h)63.91 mph (102.85 km/h)
70 mph (112.65 km/h)68.82 mph (110.76 km/h)
75 mph (120.7 km/h)73.74 mph (118.67 km/h)
80 mph (128.75 km/h)78.66 mph (126.59 km/h)
85 mph (136.79 km/h)83.57 mph (134.5 km/h)
90 mph (144.84 km/h)88.49 mph (142.41 km/h)
95 mph (152.89 km/h)93.41 mph (150.32 km/h)
100 mph (160.93 km/h)98.32 mph (158.23 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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