Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
285/30r21 vs 285/30r20 Tire Comparison Side By Side
  285/30-21 285/30-20 Difference
Diameter inches (mm) 27.73 (704.4) 26.73 (679) -1 (-25.4) -3.6%
Width inches (mm) 11.22 (285) 11.22 (285) 0 (0) 0%
Circum. inches (mm) 87.12 (2212.94) 83.98 (2133.14) -3.14 (-79.8) -3.6%
Sidewall Height inches (mm) 3.37 (85.5) 3.37 (85.5) 0 (0) 0%
Revolutions per mile (km) 727.24 (451.89) 754.45 (468.79) 27.2 (16.9) 3.7%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.28 mph (31.03 km/h)
25 mph (40.23 km/h)24.1 mph (38.78 km/h)
30 mph (48.28 km/h)28.92 mph (46.54 km/h)
35 mph (56.33 km/h)33.74 mph (54.3 km/h)
40 mph (64.37 km/h)38.56 mph (62.05 km/h)
45 mph (72.42 km/h)43.38 mph (69.81 km/h)
50 mph (80.47 km/h)48.2 mph (77.57 km/h)
55 mph (88.51 km/h)53.02 mph (85.32 km/h)
60 mph (96.56 km/h)57.84 mph (93.08 km/h)
65 mph (104.61 km/h)62.66 mph (100.84 km/h)
70 mph (112.65 km/h)67.48 mph (108.59 km/h)
75 mph (120.7 km/h)72.3 mph (116.35 km/h)
80 mph (128.75 km/h)77.12 mph (124.11 km/h)
85 mph (136.79 km/h)81.93 mph (131.86 km/h)
90 mph (144.84 km/h)86.75 mph (139.62 km/h)
95 mph (152.89 km/h)91.57 mph (147.37 km/h)
100 mph (160.93 km/h)96.39 mph (155.13 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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