Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
325/30r21 vs 275/40r20 Tire Comparison Side By Side
  325/30-21 275/40-20 Difference
Diameter inches (mm) 28.68 (728.4) 28.66 (728) -0.02 (-0.4) -0.1%
Width inches (mm) 12.8 (325) 10.83 (275) -1.97 (-50) -15.4%
Circum. inches (mm) 90.09 (2288.34) 90.04 (2287.08) -0.05 (-1.26) -0.1%
Sidewall Height inches (mm) 3.84 (97.5) 4.33 (110) 0.49 (12.5) 12.8%
Revolutions per mile (km) 703.28 (437) 703.67 (437.24) 0.39 (0.24) 0.1%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.99 mph (32.17 km/h)
25 mph (40.23 km/h)24.99 mph (40.21 km/h)
30 mph (48.28 km/h)29.98 mph (48.25 km/h)
35 mph (56.33 km/h)34.98 mph (56.3 km/h)
40 mph (64.37 km/h)39.98 mph (64.34 km/h)
45 mph (72.42 km/h)44.98 mph (72.38 km/h)
50 mph (80.47 km/h)49.97 mph (80.42 km/h)
55 mph (88.51 km/h)54.97 mph (88.47 km/h)
60 mph (96.56 km/h)59.97 mph (96.51 km/h)
65 mph (104.61 km/h)64.96 mph (104.55 km/h)
70 mph (112.65 km/h)69.96 mph (112.59 km/h)
75 mph (120.7 km/h)74.96 mph (120.63 km/h)
80 mph (128.75 km/h)79.96 mph (128.68 km/h)
85 mph (136.79 km/h)84.95 mph (136.72 km/h)
90 mph (144.84 km/h)89.95 mph (144.76 km/h)
95 mph (152.89 km/h)94.95 mph (152.8 km/h)
100 mph (160.93 km/h)99.95 mph (160.85 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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