Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
325/30r20 vs 325/35r18 Tire Comparison Side By Side
  325/30-20 325/35-18 Difference
Diameter inches (mm) 27.68 (703) 26.96 (684.7) -0.72 (-18.3) -2.6%
Width inches (mm) 12.8 (325) 12.8 (325) 0 (0) 0%
Circum. inches (mm) 86.95 (2208.54) 84.69 (2151.05) -2.26 (-57.49) -2.6%
Sidewall Height inches (mm) 3.84 (97.5) 4.48 (113.75) 0.64 (16.25) 16.7%
Revolutions per mile (km) 728.69 (452.79) 748.17 (464.89) 19.48 (12.1) 2.7%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.48 mph (31.35 km/h)
25 mph (40.23 km/h)24.35 mph (39.19 km/h)
30 mph (48.28 km/h)29.22 mph (47.02 km/h)
35 mph (56.33 km/h)34.09 mph (54.86 km/h)
40 mph (64.37 km/h)38.96 mph (62.7 km/h)
45 mph (72.42 km/h)43.83 mph (70.54 km/h)
50 mph (80.47 km/h)48.7 mph (78.37 km/h)
55 mph (88.51 km/h)53.57 mph (86.21 km/h)
60 mph (96.56 km/h)58.44 mph (94.05 km/h)
65 mph (104.61 km/h)63.31 mph (101.88 km/h)
70 mph (112.65 km/h)68.18 mph (109.72 km/h)
75 mph (120.7 km/h)73.05 mph (117.56 km/h)
80 mph (128.75 km/h)77.92 mph (125.4 km/h)
85 mph (136.79 km/h)82.79 mph (133.23 km/h)
90 mph (144.84 km/h)87.66 mph (141.07 km/h)
95 mph (152.89 km/h)92.53 mph (148.91 km/h)
100 mph (160.93 km/h)97.4 mph (156.75 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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