Tire Size Calculator

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Stock Sizes

  • 255/75-16

Plus Sizes

  • 255/75-16

Accepts P-Metric and Inches
/ R
/ R
325/30r21 vs 345/30r21 Tire Comparison Side By Side
  325/30-21 345/30-21 Difference
Diameter inches (mm) 28.68 (728.4) 29.15 (740.4) 0.47 (12) 1.6%
Width inches (mm) 12.8 (325) 13.58 (345) 0.79 (20) 6.2%
Circum. inches (mm) 90.09 (2288.34) 91.58 (2326.04) 1.48 (37.7) 1.6%
Sidewall Height inches (mm) 3.84 (97.5) 4.07 (103.5) 0.24 (6) 6.2%
Revolutions per mile (km) 703.28 (437) 691.88 (429.92) -11.4 (-7.08) -1.6%

Speedometer Difference

Speedo Reading Actual Speed
20 mph (32.19 km/h)20.33 mph (32.72 km/h)
25 mph (40.23 km/h)25.41 mph (40.9 km/h)
30 mph (48.28 km/h)30.49 mph (49.08 km/h)
35 mph (56.33 km/h)35.58 mph (57.26 km/h)
40 mph (64.37 km/h)40.66 mph (65.43 km/h)
45 mph (72.42 km/h)45.74 mph (73.61 km/h)
50 mph (80.47 km/h)50.82 mph (81.79 km/h)
55 mph (88.51 km/h)55.91 mph (89.97 km/h)
60 mph (96.56 km/h)60.99 mph (98.15 km/h)
65 mph (104.61 km/h)66.07 mph (106.33 km/h)
70 mph (112.65 km/h)71.15 mph (114.51 km/h)
75 mph (120.7 km/h)76.24 mph (122.69 km/h)
80 mph (128.75 km/h)81.32 mph (130.87 km/h)
85 mph (136.79 km/h)86.4 mph (139.05 km/h)
90 mph (144.84 km/h)91.48 mph (147.23 km/h)
95 mph (152.89 km/h)96.57 mph (155.41 km/h)
100 mph (160.93 km/h)101.65 mph (163.59 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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