Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
235/40r20 vs 235/50r18 Tire Comparison Side By Side
  235/40-20 235/50-18 Difference
Diameter inches (mm) 27.4 (696) 27.25 (692.2) -0.15 (-3.8) -0.5%
Width inches (mm) 9.25 (235) 9.25 (235) 0 (0) 0%
Circum. inches (mm) 86.08 (2186.55) 85.61 (2174.61) -0.47 (-11.94) -0.5%
Sidewall Height inches (mm) 3.7 (94) 4.63 (117.5) 0.93 (23.5) 25%
Revolutions per mile (km) 736.02 (457.34) 740.06 (459.85) 4.04 (2.51) 0.5%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.89 mph (32.01 km/h)
25 mph (40.23 km/h)24.86 mph (40.01 km/h)
30 mph (48.28 km/h)29.84 mph (48.02 km/h)
35 mph (56.33 km/h)34.81 mph (56.02 km/h)
40 mph (64.37 km/h)39.78 mph (64.02 km/h)
45 mph (72.42 km/h)44.75 mph (72.03 km/h)
50 mph (80.47 km/h)49.73 mph (80.03 km/h)
55 mph (88.51 km/h)54.7 mph (88.03 km/h)
60 mph (96.56 km/h)59.67 mph (96.03 km/h)
65 mph (104.61 km/h)64.65 mph (104.04 km/h)
70 mph (112.65 km/h)69.62 mph (112.04 km/h)
75 mph (120.7 km/h)74.59 mph (120.04 km/h)
80 mph (128.75 km/h)79.56 mph (128.04 km/h)
85 mph (136.79 km/h)84.54 mph (136.05 km/h)
90 mph (144.84 km/h)89.51 mph (144.05 km/h)
95 mph (152.89 km/h)94.48 mph (152.05 km/h)
100 mph (160.93 km/h)99.45 mph (160.06 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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