Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
145/80r18 vs 185/80r18 Tire Comparison Side By Side
  145/80-18 185/80-18 Difference
Diameter inches (mm) 27.13 (689.2) 29.65 (753.2) 2.52 (64) 9.3%
Width inches (mm) 5.71 (145) 7.28 (185) 1.57 (40) 27.6%
Circum. inches (mm) 85.24 (2165.19) 93.16 (2366.25) 7.92 (201.06) 9.3%
Sidewall Height inches (mm) 4.57 (116) 5.83 (148) 1.26 (32) 27.6%
Revolutions per mile (km) 743.28 (461.85) 680.12 (422.61) -63.16 (-39.24) -8.5%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)21.86 mph (35.18 km/h)
25 mph (40.23 km/h)27.32 mph (43.97 km/h)
30 mph (48.28 km/h)32.79 mph (52.76 km/h)
35 mph (56.33 km/h)38.25 mph (61.56 km/h)
40 mph (64.37 km/h)43.71 mph (70.35 km/h)
45 mph (72.42 km/h)49.18 mph (79.15 km/h)
50 mph (80.47 km/h)54.64 mph (87.94 km/h)
55 mph (88.51 km/h)60.11 mph (96.73 km/h)
60 mph (96.56 km/h)65.57 mph (105.53 km/h)
65 mph (104.61 km/h)71.04 mph (114.32 km/h)
70 mph (112.65 km/h)76.5 mph (123.12 km/h)
75 mph (120.7 km/h)81.96 mph (131.91 km/h)
80 mph (128.75 km/h)87.43 mph (140.7 km/h)
85 mph (136.79 km/h)92.89 mph (149.5 km/h)
90 mph (144.84 km/h)98.36 mph (158.29 km/h)
95 mph (152.89 km/h)103.82 mph (167.09 km/h)
100 mph (160.93 km/h)109.29 mph (175.88 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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