Gear Ratio Calculator for Bigger Tires

Formula

To calculate the new gear ratio (NGR):

\[ NGR = CR \times \frac{ND}{OD} \]

Where:

\(NGR\) is the new gear ratio
\(CR\) is the current gear ratio
\(ND\) is the new tire diameter (inches)
\(OD\) is the old tire diameter (inches)

What is the Gear Ratio?

The gear ratio is the ratio of the number of rotations of the input shaft (from the engine) to the number of rotations of the output shaft (to the wheels). Changing tire size affects the effective gear ratio, which can impact vehicle performance.

Example Calculation 1

Let's assume the following values:

Current Gear Ratio (\(CR\)) = 4.0
Old Tire Diameter (\(OD\)) = 30 inches
New Tire Diameter (\(ND\)) = 35 inches

Using the formula:

\[ NGR = 4.0 \times \frac{35}{30} = 4.6667 \]

The new gear ratio is 4.6667.

Example Calculation 2

Let's assume the following values:

Current Gear Ratio (\(CR\)) = 3.5
Old Tire Diameter (\(OD\)) = 28 inches
New Tire Diameter (\(ND\)) = 33 inches

Using the formula:

\[ NGR = 3.5 \times \frac{33}{28} = 4.125 \]

The new gear ratio is 4.125.