Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
325/25r21 vs 245/30r21 Tire Comparison Side By Side
  325/25-21 245/30-21 Difference
Diameter inches (mm) 27.4 (695.9) 26.79 (680.4) -0.61 (-15.5) -2.2%
Width inches (mm) 12.8 (325) 9.65 (245) -3.15 (-80) -24.6%
Circum. inches (mm) 86.07 (2186.23) 84.16 (2137.54) -1.92 (-48.69) -2.2%
Sidewall Height inches (mm) 3.2 (81.25) 2.89 (73.5) -0.31 (-7.75) -9.5%
Revolutions per mile (km) 736.13 (457.41) 752.9 (467.83) 16.77 (10.42) 2.3%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)19.55 mph (31.47 km/h)
25 mph (40.23 km/h)24.44 mph (39.34 km/h)
30 mph (48.28 km/h)29.33 mph (47.21 km/h)
35 mph (56.33 km/h)34.22 mph (55.07 km/h)
40 mph (64.37 km/h)39.11 mph (62.94 km/h)
45 mph (72.42 km/h)44 mph (70.81 km/h)
50 mph (80.47 km/h)48.89 mph (78.68 km/h)
55 mph (88.51 km/h)53.77 mph (86.54 km/h)
60 mph (96.56 km/h)58.66 mph (94.41 km/h)
65 mph (104.61 km/h)63.55 mph (102.28 km/h)
70 mph (112.65 km/h)68.44 mph (110.15 km/h)
75 mph (120.7 km/h)73.33 mph (118.01 km/h)
80 mph (128.75 km/h)78.22 mph (125.88 km/h)
85 mph (136.79 km/h)83.11 mph (133.75 km/h)
90 mph (144.84 km/h)88 mph (141.62 km/h)
95 mph (152.89 km/h)92.88 mph (149.48 km/h)
100 mph (160.93 km/h)97.77 mph (157.35 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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