Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
255/30r21 vs 305/25r21 Tire Comparison Side By Side
  255/30-21 305/25-21 Difference
Diameter inches (mm) 27.02 (686.4) 27 (685.9) -0.02 (-0.5) -0.1%
Width inches (mm) 10.04 (255) 12.01 (305) 1.97 (50) 19.6%
Circum. inches (mm) 84.9 (2156.39) 84.84 (2154.82) -0.06 (-1.57) -0.1%
Sidewall Height inches (mm) 3.01 (76.5) 3 (76.25) -0.01 (-0.25) -0.3%
Revolutions per mile (km) 746.31 (463.74) 746.86 (464.08) 0.54 (0.34) 0.1%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.99 mph (32.16 km/h)
25 mph (40.23 km/h)24.98 mph (40.2 km/h)
30 mph (48.28 km/h)29.98 mph (48.25 km/h)
35 mph (56.33 km/h)34.97 mph (56.29 km/h)
40 mph (64.37 km/h)39.97 mph (64.33 km/h)
45 mph (72.42 km/h)44.97 mph (72.37 km/h)
50 mph (80.47 km/h)49.96 mph (80.41 km/h)
55 mph (88.51 km/h)54.96 mph (88.45 km/h)
60 mph (96.56 km/h)59.96 mph (96.49 km/h)
65 mph (104.61 km/h)64.95 mph (104.53 km/h)
70 mph (112.65 km/h)69.95 mph (112.57 km/h)
75 mph (120.7 km/h)74.95 mph (120.61 km/h)
80 mph (128.75 km/h)79.94 mph (128.65 km/h)
85 mph (136.79 km/h)84.94 mph (136.69 km/h)
90 mph (144.84 km/h)89.93 mph (144.74 km/h)
95 mph (152.89 km/h)94.93 mph (152.78 km/h)
100 mph (160.93 km/h)99.93 mph (160.82 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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