Tire Size Calculator
This converter requires the use of Javascript enabled and capable browsers. These calculators are designed to give the approximate tire size (diameter from ground to top of the tire while mounted on the vehicle), based on data entered. That data consists of the ring gear and pinion gear ratio, the target speed of the vehicle and the transmission final gear ratio. The default values are for a typical V8 small block Chevrolet vehicle, however you may enter any legal value you wish. The first calculator assumes you want all the possible tire size change reflective values. The changes show what a tire size change would do to speed. While the math is exact, tires only come in certain sizes so you would need to select the closest possible size to your needs. The second calculator shows the required tire size for the values you entered. The higher the RGP ratio, the lower the top end speed but faster acceleration and more pulling power. The same is true of the transmission final gear ratio. Although there is a point of diminishing returns, the larger the tire diameter, the higher the potential speed. We do assume safe tire air pressure and tread. The calculator does not take into consideration any drive train loss, road and weather conditions or driver skills. The calculated results are displayed; the higher the engine RPM, the greater the potential speed at the cost of fuel, heat, friction and engine longevity. We urge you to drive safely.
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Designation
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Number
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Various Tire Size Change Calculations
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Required Data Entry
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| Ring Gear and Pinion Ratio (3.08, 3.55, etc.) |
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| Engine RPM |
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| Target Vehicle MPH |
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| Transmission Final Gear Ratio (2.54, 1.43, 1.00, etc.) |
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Calculated Results From Change Of YOur Entry
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Speed Changes
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Tire Size Changes
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| A MPH Change To MPH (-6%) |
Inches |
| A MPH Change To MPH (-3%) |
Inches |
| Tire Height - Your Entered Values |
Inches |
| A MPH Change To MPH (+3%) |
Inches |
| A MPH Change To MPH (+6%) |
Inches |
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Designation
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Number
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Tire Size Calculation Manual Entry
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Required Data Entry
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| Ring Gear and Pinion Ratio (3.08, 3.55, etc.) |
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| Engine RPM |
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| Target Vehicle MPH |
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| Transmission Final Gear Ratio (2.54, 1.43, 1.00, etc.) |
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Calculated Results
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| Tire Height Required |
Inches
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Updated 8.15.11
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