Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
245/45r18 vs 245/40r20 Tire Comparison Side By Side
  245/45-18 245/40-20 Difference
Diameter inches (mm) 26.68 (677.7) 27.72 (704) 1.04 (26.3) 3.9%
Width inches (mm) 9.65 (245) 9.65 (245) 0 (0) 0%
Circum. inches (mm) 83.82 (2129.06) 87.07 (2211.68) 3.25 (82.62) 3.9%
Sidewall Height inches (mm) 4.34 (110.25) 3.86 (98) -0.48 (-12.25) -11.1%
Revolutions per mile (km) 755.9 (469.69) 727.66 (452.14) -28.24 (-17.55) -3.7%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)20.78 mph (33.44 km/h)
25 mph (40.23 km/h)25.97 mph (41.8 km/h)
30 mph (48.28 km/h)31.16 mph (50.15 km/h)
35 mph (56.33 km/h)36.36 mph (58.51 km/h)
40 mph (64.37 km/h)41.55 mph (66.87 km/h)
45 mph (72.42 km/h)46.75 mph (75.23 km/h)
50 mph (80.47 km/h)51.94 mph (83.59 km/h)
55 mph (88.51 km/h)57.13 mph (91.95 km/h)
60 mph (96.56 km/h)62.33 mph (100.31 km/h)
65 mph (104.61 km/h)67.52 mph (108.67 km/h)
70 mph (112.65 km/h)72.72 mph (117.03 km/h)
75 mph (120.7 km/h)77.91 mph (125.39 km/h)
80 mph (128.75 km/h)83.1 mph (133.74 km/h)
85 mph (136.79 km/h)88.3 mph (142.1 km/h)
90 mph (144.84 km/h)93.49 mph (150.46 km/h)
95 mph (152.89 km/h)98.69 mph (158.82 km/h)
100 mph (160.93 km/h)103.88 mph (167.18 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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