Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
180/60r15 vs 185/65r15 Tire Comparison Side By Side
  180/60-15 185/65-15 Difference
Diameter inches (mm) 23.5 (597) 24.47 (621.5) 0.96 (24.5) 4.1%
Width inches (mm) 7.09 (180) 7.28 (185) 0.2 (5) 2.8%
Circum. inches (mm) 73.84 (1875.53) 76.87 (1952.5) 3.03 (76.97) 4.1%
Sidewall Height inches (mm) 4.25 (108) 4.73 (120.25) 0.48 (12.25) 11.3%
Revolutions per mile (km) 858.07 (533.18) 824.25 (512.16) -33.83 (-21.02) -3.9%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)20.82 mph (33.51 km/h)
25 mph (40.23 km/h)26.03 mph (41.88 km/h)
30 mph (48.28 km/h)31.23 mph (50.26 km/h)
35 mph (56.33 km/h)36.44 mph (58.64 km/h)
40 mph (64.37 km/h)41.64 mph (67.02 km/h)
45 mph (72.42 km/h)46.85 mph (75.39 km/h)
50 mph (80.47 km/h)52.05 mph (83.77 km/h)
55 mph (88.51 km/h)57.26 mph (92.15 km/h)
60 mph (96.56 km/h)62.46 mph (100.52 km/h)
65 mph (104.61 km/h)67.67 mph (108.9 km/h)
70 mph (112.65 km/h)72.87 mph (117.28 km/h)
75 mph (120.7 km/h)78.08 mph (125.65 km/h)
80 mph (128.75 km/h)83.28 mph (134.03 km/h)
85 mph (136.79 km/h)88.49 mph (142.41 km/h)
90 mph (144.84 km/h)93.69 mph (150.79 km/h)
95 mph (152.89 km/h)98.9 mph (159.16 km/h)
100 mph (160.93 km/h)104.1 mph (167.54 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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