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 115/90r18 Tire Comparison Side By Side
  120/85-18 115/90-18 Difference
Diameter inches (mm) 26.03 (661.2) 26.15 (664.2) 0.12 (3) 0.5%
Width inches (mm) 4.72 (120) 4.53 (115) -0.2 (-5) -4.2%
Circum. inches (mm) 81.78 (2077.22) 82.15 (2086.65) 0.37 (9.42) 0.5%
Sidewall Height inches (mm) 4.02 (102) 4.07 (103.5) 0.06 (1.5) 1.5%
Revolutions per mile (km) 774.76 (481.41) 771.26 (479.24) -3.5 (-2.17) -0.5%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)20.09 mph (32.33 km/h)
25 mph (40.23 km/h)25.11 mph (40.42 km/h)
30 mph (48.28 km/h)30.14 mph (48.5 km/h)
35 mph (56.33 km/h)35.16 mph (56.58 km/h)
40 mph (64.37 km/h)40.18 mph (64.67 km/h)
45 mph (72.42 km/h)45.2 mph (72.75 km/h)
50 mph (80.47 km/h)50.23 mph (80.83 km/h)
55 mph (88.51 km/h)55.25 mph (88.92 km/h)
60 mph (96.56 km/h)60.27 mph (97 km/h)
65 mph (104.61 km/h)65.29 mph (105.08 km/h)
70 mph (112.65 km/h)70.32 mph (113.17 km/h)
75 mph (120.7 km/h)75.34 mph (121.25 km/h)
80 mph (128.75 km/h)80.36 mph (129.33 km/h)
85 mph (136.79 km/h)85.39 mph (137.42 km/h)
90 mph (144.84 km/h)90.41 mph (145.5 km/h)
95 mph (152.89 km/h)95.43 mph (153.58 km/h)
100 mph (160.93 km/h)100.45 mph (161.66 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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