Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
255/45r20 vs 255/40r21 Tire Comparison Side By Side
  255/45-20 255/40-21 Difference
Diameter inches (mm) 29.04 (737.5) 29.03 (737.4) -0 (-0.1) -0%
Width inches (mm) 10.04 (255) 10.04 (255) 0 (0) 0%
Circum. inches (mm) 91.22 (2316.92) 91.21 (2316.61) -0.01 (-0.31) -0%
Sidewall Height inches (mm) 4.52 (114.75) 4.02 (102) -0.5 (-12.75) -11.1%
Revolutions per mile (km) 694.6 (431.61) 694.7 (431.66) 0.09 (0.06) 0%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)20 mph (32.18 km/h)
25 mph (40.23 km/h)25 mph (40.23 km/h)
30 mph (48.28 km/h)30 mph (48.27 km/h)
35 mph (56.33 km/h)35 mph (56.32 km/h)
40 mph (64.37 km/h)39.99 mph (64.37 km/h)
45 mph (72.42 km/h)44.99 mph (72.41 km/h)
50 mph (80.47 km/h)49.99 mph (80.46 km/h)
55 mph (88.51 km/h)54.99 mph (88.5 km/h)
60 mph (96.56 km/h)59.99 mph (96.55 km/h)
65 mph (104.61 km/h)64.99 mph (104.59 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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