Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
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185/65r15 vs 235/40r18 Tire Comparison Side By Side
  185/65-15 235/40-18 Difference
Diameter inches (mm) 24.47 (621.5) 25.4 (645.2) 0.93 (23.7) 3.8%
Width inches (mm) 7.28 (185) 9.25 (235) 1.97 (50) 27%
Circum. inches (mm) 76.87 (1952.5) 79.8 (2026.96) 2.93 (74.46) 3.8%
Sidewall Height inches (mm) 4.73 (120.25) 3.7 (94) -1.03 (-26.25) -21.8%
Revolutions per mile (km) 824.25 (512.16) 793.97 (493.35) -30.28 (-18.81) -3.7%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)20.76 mph (33.41 km/h)
25 mph (40.23 km/h)25.95 mph (41.77 km/h)
30 mph (48.28 km/h)31.14 mph (50.12 km/h)
35 mph (56.33 km/h)36.33 mph (58.48 km/h)
40 mph (64.37 km/h)41.53 mph (66.83 km/h)
45 mph (72.42 km/h)46.72 mph (75.18 km/h)
50 mph (80.47 km/h)51.91 mph (83.54 km/h)
55 mph (88.51 km/h)57.1 mph (91.89 km/h)
60 mph (96.56 km/h)62.29 mph (100.24 km/h)
65 mph (104.61 km/h)67.48 mph (108.6 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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