Tire Size Gear Ratio Calculator
Calculate your vehicle's gear ratio based on tire size. This tool helps you determine how different tire sizes affect the performance of your vehicle's drivetrain.
Enter Tire Size
Understanding Gear Ratios and Tire Sizes
Your vehicle's tire size directly impacts its gear ratio. When you change your tire size, the overall gear ratio changes, affecting your speed, acceleration, and fuel economy. This section will explain how tire size affects your gear ratio and performance.
How Tire Size Affects Gear Ratio
Changing your tire size alters the circumference of your tires, which in turn affects how far your vehicle travels with each rotation of the wheels. The gear ratio will change based on the new effective tire diameter. Here's how it works:
- Increased tire diameter = lower effective gear ratio (slower acceleration, higher top speed)
- Decreased tire diameter = higher effective gear ratio (faster acceleration, lower top speed)
Formula to Calculate Effective Gear Ratio
To calculate the effective gear ratio with a new tire size, use this formula:
| Formula |
|---|
| New Gear Ratio = (Current Gear Ratio × Old Tire Diameter) ÷ New Tire Diameter |
What Is the Tire Diameter?
The tire diameter is calculated from the width, aspect ratio, and rim size. Use the following formula to calculate the diameter:
| Formula |
|---|
| Diameter (inches) = (Tire Width × Aspect Ratio ÷ 100 × 2) ÷ 25.4 + Rim Diameter |
Frequently Asked Questions
Why does tire size affect the gear ratio?
When you change the tire size, you change the number of revolutions per mile that the tire makes. This alters the overall drive ratio, which affects acceleration and speed. For example, larger tires cover more distance per revolution, which makes your vehicle feel slower at lower speeds and faster at higher speeds.
How do I calculate my tire diameter?
To calculate your tire diameter, you'll need to know your tire width, aspect ratio, and rim diameter. Use the formula provided in the guide to compute the tire diameter.
Will changing tire size affect my speedometer?
Yes, changing your tire size will impact the accuracy of your speedometer. Larger tires will make the speedometer read slower than your actual speed, while smaller tires will make it read faster. Adjusting the gear ratio can help compensate for this change.
What’s the ideal gear ratio for my vehicle?
The ideal gear ratio depends on your driving needs. A lower gear ratio (e.g., 3.08) is good for highway cruising, while a higher gear ratio (e.g., 4.10) is better for performance and acceleration. Consider your vehicle's primary use when choosing the right gear ratio.