Gear Chart A HELPFUL HINT FROM 4X4 CONNECTION Did you know that when changing tire size, it is imperative that you change gear ratios accordingly for your vehicle to maintain PEAK PERFORMANCE. The Chart below will help you choose the right gear set ratio for your application. When selecting a Gear Ratio, you should consider the following: 1. Tire Size 2. Transmission Ratio 3. Final Gear Ratio 4. Engine RPM at Cruise Speed The following formula has been developed to calculate the optimum final Gear Ratio and Tire Diameter. According to this chart, the acceptable RPM range is 2000-3000 which is represented by the entire shaded area of the chart. The optimum RPM range is 2300-2600, and is represented by the light yellow shading. When changing ratios to improve mileage, choose a ratio within the dark yellow shaded band below the optimum range.