Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
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155/85r18 vs 145/85r18 Tire Comparison Side By Side
  155/85-18 145/85-18 Difference
Diameter inches (mm) 28.37 (720.7) 27.7 (703.7) -0.67 (-17) -2.4%
Width inches (mm) 6.1 (155) 5.71 (145) -0.39 (-10) -6.5%
Circum. inches (mm) 89.14 (2264.15) 87.04 (2210.74) -2.1 (-53.41) -2.4%
Sidewall Height inches (mm) 5.19 (131.75) 4.85 (123.25) -0.33 (-8.5) -6.5%
Revolutions per mile (km) 710.8 (441.67) 727.97 (452.34) 17.17 (10.67) 2.4%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.53 mph (31.43 km/h)
25 mph (40.23 km/h)24.41 mph (39.28 km/h)
30 mph (48.28 km/h)29.29 mph (47.14 km/h)
35 mph (56.33 km/h)34.17 mph (55 km/h)
40 mph (64.37 km/h)39.06 mph (62.86 km/h)
45 mph (72.42 km/h)43.94 mph (70.71 km/h)
50 mph (80.47 km/h)48.82 mph (78.57 km/h)
55 mph (88.51 km/h)53.7 mph (86.43 km/h)
60 mph (96.56 km/h)58.58 mph (94.28 km/h)
65 mph (104.61 km/h)63.47 mph (102.14 km/h)
70 mph (112.65 km/h)68.35 mph (110 km/h)
75 mph (120.7 km/h)73.23 mph (117.85 km/h)
80 mph (128.75 km/h)78.11 mph (125.71 km/h)
85 mph (136.79 km/h)83 mph (133.57 km/h)
90 mph (144.84 km/h)87.88 mph (141.42 km/h)
95 mph (152.89 km/h)92.76 mph (149.28 km/h)
100 mph (160.93 km/h)97.64 mph (157.14 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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