Speedometer Correction Calculator
Calculate how different tire sizes affect your speedometer accuracy.
Speedometer Correction Calculator
When you change your tire size, your speedometer reading can become inaccurate. This calculator helps you determine the true speed of your vehicle with new tires.
About Speedometer Accuracy
When you change your tire size, your vehicle's speedometer reading can become inaccurate because it's calibrated based on the original tire's diameter. Here's why:
- Your speedometer measures the rotational speed of your transmission or wheels
- It converts this to vehicle speed based on the assumption that your tires have a specific diameter
- Larger diameter tires travel farther in one rotation than smaller diameter tires
- Therefore, changing tire size affects the relationship between wheel rotation and actual vehicle speed
How Tire Size Affects Speedometer Reading
- Larger Tires: Your actual speed will be faster than what your speedometer shows
- Smaller Tires: Your actual speed will be slower than what your speedometer shows
Important Safety Considerations
Speedometer inaccuracy can lead to unintentionally speeding or driving too slowly, which can be dangerous and may result in traffic violations.
If you've changed your tire size significantly:
- Consider getting your speedometer recalibrated professionally
- Use a GPS device to verify your actual speed
- Adjust your driving accordingly based on the calculations from this tool
Remember: In many jurisdictions, having an inaccurate speedometer is not a legal defense for speeding tickets.