Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
305/75r20 vs 285/65r20 Tire Comparison Side By Side
  305/75-20 285/65-20 Difference
Diameter inches (mm) 38.01 (965.5) 34.59 (878.5) -3.43 (-87) -9%
Width inches (mm) 12.01 (305) 11.22 (285) -0.79 (-20) -6.6%
Circum. inches (mm) 119.42 (3033.21) 108.66 (2759.89) -10.76 (-273.32) -9%
Sidewall Height inches (mm) 9.01 (228.75) 7.29 (185.25) -1.71 (-43.5) -19%
Revolutions per mile (km) 530.57 (329.68) 583.12 (362.33) 52.54 (32.65) 9.9%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)18.2 mph (29.29 km/h)
25 mph (40.23 km/h)22.75 mph (36.61 km/h)
30 mph (48.28 km/h)27.3 mph (43.93 km/h)
35 mph (56.33 km/h)31.85 mph (51.25 km/h)
40 mph (64.37 km/h)36.4 mph (58.57 km/h)
45 mph (72.42 km/h)40.95 mph (65.89 km/h)
50 mph (80.47 km/h)45.49 mph (73.22 km/h)
55 mph (88.51 km/h)50.04 mph (80.54 km/h)
60 mph (96.56 km/h)54.59 mph (87.86 km/h)
65 mph (104.61 km/h)59.14 mph (95.18 km/h)
70 mph (112.65 km/h)63.69 mph (102.5 km/h)
75 mph (120.7 km/h)68.24 mph (109.82 km/h)
80 mph (128.75 km/h)72.79 mph (117.15 km/h)
85 mph (136.79 km/h)77.34 mph (124.47 km/h)
90 mph (144.84 km/h)81.89 mph (131.79 km/h)
95 mph (152.89 km/h)86.44 mph (139.11 km/h)
100 mph (160.93 km/h)90.99 mph (146.43 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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