1. What is a Tire Size Change Speed Calculator?

Definition: This calculator determines how changing your tire size affects your vehicle's speedometer reading.

Purpose: It helps vehicle owners and mechanics understand speedometer calibration needs when installing different sized tires.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S_{new} \) — Actual speed with new tires (mph)
• \( S_{old} \) — Speedometer reading (mph)
• \( TD_{new} \) — Diameter of new tires (inches)
• \( TD_{old} \) — Diameter of original tires (inches)

Explanation: The speed difference is proportional to the change in tire diameter - larger tires make your actual speed higher than indicated, while smaller tires make it lower.

3. Importance of Speed Calculation

Details: Proper speed calculation ensures accurate speedometer readings, helps maintain proper gearing, and prevents speeding tickets from incorrect speed readings.

4. Using the Calculator

Tips: Enter your original speedometer reading, original tire diameter, and new tire diameter. All values must be > 0. Measure tire diameter accurately for best results.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure my tire diameter?
A: Measure from the ground to the top of the tire (while loaded) or calculate using: (wheel diameter) + 2*(sidewall height).

Q2: What if I change both width and aspect ratio?
A: The calculator still works as long as you know the overall diameter difference. The formula depends only on diameter, not width.

Q3: How does this affect my odometer?
A: The same ratio applies - larger tires cause your odometer to undercount miles, smaller tires make it overcount.

Q4: What's a typical tire diameter change?
A: Most tire changes alter diameter by 1-3 inches. More than 3 inches may require speedometer recalibration.

Q5: Does this account for tire wear?
A: No, the calculation assumes new tires. Worn tires would have slightly smaller diameters.