Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
225/40r20 vs 225/45r18 Tire Comparison Side By Side
  225/40-20 225/45-18 Difference
Diameter inches (mm) 27.09 (688) 25.97 (659.7) -1.11 (-28.3) -4.1%
Width inches (mm) 8.86 (225) 8.86 (225) 0 (0) 0%
Circum. inches (mm) 85.1 (2161.42) 81.59 (2072.51) -3.5 (-88.91) -4.1%
Sidewall Height inches (mm) 3.54 (90) 3.99 (101.25) 0.44 (11.25) 12.5%
Revolutions per mile (km) 744.58 (462.66) 776.52 (482.51) 31.94 (19.85) 4.3%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.18 mph (30.86 km/h)
25 mph (40.23 km/h)23.97 mph (38.58 km/h)
30 mph (48.28 km/h)28.77 mph (46.29 km/h)
35 mph (56.33 km/h)33.56 mph (54.01 km/h)
40 mph (64.37 km/h)38.35 mph (61.73 km/h)
45 mph (72.42 km/h)43.15 mph (69.44 km/h)
50 mph (80.47 km/h)47.94 mph (77.16 km/h)
55 mph (88.51 km/h)52.74 mph (84.87 km/h)
60 mph (96.56 km/h)57.53 mph (92.59 km/h)
65 mph (104.61 km/h)62.33 mph (100.3 km/h)
70 mph (112.65 km/h)67.12 mph (108.02 km/h)
75 mph (120.7 km/h)71.91 mph (115.74 km/h)
80 mph (128.75 km/h)76.71 mph (123.45 km/h)
85 mph (136.79 km/h)81.5 mph (131.17 km/h)
90 mph (144.84 km/h)86.3 mph (138.88 km/h)
95 mph (152.89 km/h)91.09 mph (146.6 km/h)
100 mph (160.93 km/h)95.89 mph (154.31 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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