Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
235/85r15 vs 30/9.5r15 Tire Comparison Side By Side
  235/85-15 30/9.5-15 Difference
Diameter inches (mm) 30.73 (780.5) 29.99 (761.78) -0.74 (-18.72) -2.4%
Width inches (mm) 9.25 (235) 9.49 (241) 0.24 (6) 2.6%
Circum. inches (mm) 96.54 (2452.01) 94.22 (2393.2) -2.32 (-58.81) -2.4%
Sidewall Height inches (mm) 7.86 (199.75) 7.5 (190.39) -0.37 (-9.36) -4.7%
Revolutions per mile (km) 656.34 (407.83) 672.46 (417.85) 16.13 (10.02) 2.5%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.52 mph (31.41 km/h)
25 mph (40.23 km/h)24.4 mph (39.27 km/h)
30 mph (48.28 km/h)29.28 mph (47.12 km/h)
35 mph (56.33 km/h)34.16 mph (54.98 km/h)
40 mph (64.37 km/h)39.04 mph (62.83 km/h)
45 mph (72.42 km/h)43.92 mph (70.68 km/h)
50 mph (80.47 km/h)48.8 mph (78.54 km/h)
55 mph (88.51 km/h)53.68 mph (86.39 km/h)
60 mph (96.56 km/h)58.56 mph (94.24 km/h)
65 mph (104.61 km/h)63.44 mph (102.1 km/h)
70 mph (112.65 km/h)68.32 mph (109.95 km/h)
75 mph (120.7 km/h)73.2 mph (117.81 km/h)
80 mph (128.75 km/h)78.08 mph (125.66 km/h)
85 mph (136.79 km/h)82.96 mph (133.51 km/h)
90 mph (144.84 km/h)87.84 mph (141.37 km/h)
95 mph (152.89 km/h)92.72 mph (149.22 km/h)
100 mph (160.93 km/h)97.6 mph (157.07 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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