1. What is a Tire Size And Speed Comparison Calculator?

Definition: This calculator compares vehicle speeds when changing tire sizes, showing how the actual speed differs from the speedometer reading.

Purpose: It helps drivers understand how changing tire sizes affects their actual speed, which is important for safety and speed limit compliance.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \text{S\_new} \) — Actual speed with new tires (mph)
• \( \text{S\_old} \) — Speedometer reading (mph)
• \( \text{D\_new} \) — Diameter of new tires (inches)
• \( \text{D\_old} \) — Diameter of original tires (inches)

Explanation: The speed difference occurs because larger tires rotate fewer times per mile than smaller tires, while the speedometer is calibrated for the original tire size.

3. Importance of Speed Comparison

Details: Understanding this difference helps prevent speeding tickets (when using larger tires) or driving too slowly (when using smaller tires).

4. Using the Calculator

Tips: Enter your speedometer reading, original tire diameter, and new tire diameter. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: How do I find my tire diameter?
A: Check your tire sidewall for size (e.g., 235/75R15) and use a tire size calculator to determine diameter.

Q2: Will larger tires always increase my speed?
A: Yes, if your speedometer shows 60 mph but you have larger tires, your actual speed will be higher.

Q3: How accurate is this calculation?
A: Very accurate for comparing theoretical speeds, but actual results may vary slightly due to tire pressure and wear.

Q4: Does this affect odometer readings?
A: Yes, larger tires will cause your odometer to underreport mileage, while smaller tires overreport.

Q5: Should I recalibrate my speedometer after changing tire sizes?
A: For significant changes (3% or more difference), professional recalibration is recommended.