Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
225/80r15 vs 31/8.5r15 Tire Comparison Side By Side
  225/80-15 31/8.5-15 Difference
Diameter inches (mm) 29.17 (741) 30.99 (787.08) 1.81 (46.08) 6.2%
Width inches (mm) 8.86 (225) 8.5 (216) -0.35 (-9) -4%
Circum. inches (mm) 91.65 (2327.92) 97.35 (2472.68) 5.7 (144.76) 6.2%
Sidewall Height inches (mm) 7.09 (180) 7.99 (203.04) 0.91 (23.04) 12.8%
Revolutions per mile (km) 691.32 (429.57) 650.85 (404.42) -40.47 (-25.15) -5.9%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)21.24 mph (34.19 km/h)
25 mph (40.23 km/h)26.55 mph (42.74 km/h)
30 mph (48.28 km/h)31.87 mph (51.28 km/h)
35 mph (56.33 km/h)37.18 mph (59.83 km/h)
40 mph (64.37 km/h)42.49 mph (68.38 km/h)
45 mph (72.42 km/h)47.8 mph (76.92 km/h)
50 mph (80.47 km/h)53.11 mph (85.47 km/h)
55 mph (88.51 km/h)58.42 mph (94.02 km/h)
60 mph (96.56 km/h)63.73 mph (102.57 km/h)
65 mph (104.61 km/h)69.04 mph (111.11 km/h)
70 mph (112.65 km/h)74.35 mph (119.66 km/h)
75 mph (120.7 km/h)79.66 mph (128.21 km/h)
80 mph (128.75 km/h)84.97 mph (136.75 km/h)
85 mph (136.79 km/h)90.29 mph (145.3 km/h)
90 mph (144.84 km/h)95.6 mph (153.85 km/h)
95 mph (152.89 km/h)100.91 mph (162.4 km/h)
100 mph (160.93 km/h)106.22 mph (170.94 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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