Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
285/40r21 vs 265/45r21 Tire Comparison Side By Side
  285/40-21 265/45-21 Difference
Diameter inches (mm) 29.98 (761.4) 30.39 (771.9) 0.41 (10.5) 1.4%
Width inches (mm) 11.22 (285) 10.43 (265) -0.79 (-20) -7%
Circum. inches (mm) 94.17 (2392.01) 95.47 (2425) 1.3 (32.99) 1.4%
Sidewall Height inches (mm) 4.49 (114) 4.69 (119.25) 0.21 (5.25) 4.6%
Revolutions per mile (km) 672.8 (418.06) 663.65 (412.37) -9.15 (-5.69) -1.4%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)20.28 mph (32.63 km/h)
25 mph (40.23 km/h)25.34 mph (40.79 km/h)
30 mph (48.28 km/h)30.41 mph (48.95 km/h)
35 mph (56.33 km/h)35.48 mph (57.1 km/h)
40 mph (64.37 km/h)40.55 mph (65.26 km/h)
45 mph (72.42 km/h)45.62 mph (73.42 km/h)
50 mph (80.47 km/h)50.69 mph (81.58 km/h)
55 mph (88.51 km/h)55.76 mph (89.73 km/h)
60 mph (96.56 km/h)60.83 mph (97.89 km/h)
65 mph (104.61 km/h)65.9 mph (106.05 km/h)
70 mph (112.65 km/h)70.97 mph (114.21 km/h)
75 mph (120.7 km/h)76.03 mph (122.37 km/h)
80 mph (128.75 km/h)81.1 mph (130.52 km/h)
85 mph (136.79 km/h)86.17 mph (138.68 km/h)
90 mph (144.84 km/h)91.24 mph (146.84 km/h)
95 mph (152.89 km/h)96.31 mph (155 km/h)
100 mph (160.93 km/h)101.38 mph (163.15 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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